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Sludge is one of the by-products of wastewater treatment plants (WWTPs). To assist biological processes, part of the produced sludge is returned to the treatment process and the excess is removed from the treatment plant whereby it undergoes thickening and dewatering. Numerous studies have been conducted to investigate the effect of different coagulants on dewatering from sludge, but the effect of using divalent iron for this purpose has not been investigated so far. In this research, the effect of divalent and trivalent iron compounds (ferrous sulfate and ferric chloride) on the dewatering of excess sludge of the first module of the Bojnourd WWTP (Iran) has been investigated. In this regard, first, the effect of different doses of each coagulant to optimize the dewatering characteristics of sludge was investigated and then the effect of pH change by adding lime was investigated. The results showed that the addition of optimal doses of FeSO4 (0.6 and 0.4 g/l) and lime (0.664 and 1.5866 g/l) reduced the capillary suction time of sludge by 30.6 and 32.7%, respectively, while reducing the moisture content of sludge cake by 26 and 30.6%.

The combination of a submerged anaerobic membrane bioreactor (SAnMBR) and two biowaste adsorption columns (eggshell (EGSL) and seagrass (SG)) was studied for the first time to evaluate the recovery of phosphates from wastewater. Reject wastewater from anaerobic sludge dewatering process was fed into the SAnMBR and the results showed a COD removal of 50%. The phosphate removal efficiency was low and as such, the effluent from SAnMBR was then passed through two columns containing thermally treated eggshell and seagrass residues for further phosphate removal. The final effluent analysis confirmed that phosphates could be additionally removed resulting in over 95% recovery (flow rate 0.3 L d−1), for both biowaste materials. The ammonium and COD removal after the adsorption columns was low, indicating the high selectivity towards phosphates. Moreover, the solid residues after adsorption were evaluated as soil conditioners on Lepidium sativum and Sinapis alba seeds. The SG end product exhibited high GI values for both seeds tested indicating a positive effect on plant growth, while the EGSL end product negatively affected the seed germination. The fractionation analysis of phosphorus showed that inorganically bound phosphorus (IP) was the major phosphorus fraction in EGSL and SG end product, accounting for 92.6 and 95.7% of TP, respectively. The results of this study suggest that the SG and EGSL could be effectively reclaimed as selective adsorbents towards phosphates in combination with a SAnMBR and the SG solid residues after adsorption can be directly applied for agricultural purposes, contributing to the development of a zero-waste technology.

The ever-present environmental crises are current research hotspots. Nature-based solutions have been shown to have multiple co-benefits toward solving these crises. Plant-based coagulants are known to be a cost-effective and environmentally friendly approach for coagulation and flocculation processes for drinking-water treatment. In this study, a natural coagulant was extracted from Annona diversifolia seed, and its effectiveness was investigated for turbidity reduction using jar test in kaolin suspension, river water, and evaluation of factors for sludge dewatering. The characterisation studies of Annona diversifolia seed extract were carried out using techniques including Fourier-transform infrared spectroscopy (FTIR), zeta potential analyser, and transmission electron microscopy (TEM). Response surface methodology (RSM) was also performed for the optimisation study. The results from FTIR showed that Annona diversifolia seed extract contains carboxyl and hydroxyl functional groups. The charge density was found to be negative. A web-like structure surface morphology was observed from TEM. The optimum treatment settings were found to be at pH 3 and a dosage of 25 mg/L for water treatment, and 50 mg/L for sludge dewatering, which were comparable to the metal–salts coagulants. Annona diversifolia seed extract has been shown to be a good natural coagulant. Further research can be conducted to modify and enhance its performance.

Most sludges are dewatered using mechanical dewatering systems that can bring the weight percentage of the sludge solids up to a maximum of about 40 TS%. This study examined a new way to enhance pr...

Moringa Oleifera (MO) is a highly effective conditioner in the dewatering of Fecal sludge (FS). However, the model for the prediction of its optimal dose has not yet been documented. This article presents the results of the developed model for the prediction of MO optimal doses. The developed model was based on assessing the FS parameters and MO stock solution. The FS samples were obtained from a mixture of a pit latrine and septic tank and were analyzed at the water quality laboratory of the University of Dar es Salaam. The multiple linear regression model was used to establish a relationship between MO optimal dose as a function of FS characteristics (pH, Electrical Conductivity, Total Solids and Total Suspended Solids) and concentration of MO stock solution. The results indicated that the main contributing factors which determine the MO optimal dose were the concentration of MO stock solution, followed by pH of FS. The model results showed a good agreement between the predicted and observed MO optimal dose with a coefficient of determination of R2 = 0.72 and 0.9 for calibration and validation respectively. Therefore, the model can be adapted to determine the MO optimal dose without running the Jar-test experiment.

Рассмотрены разработанные компанией Alfa Laval инновационные технологические решения, воплощенные в декантерной центрифуге Aldec G3. Для обезвоживания осадков сточных вод компания Alfa Laval изготавливает два вида современных декантерных центрифуг (всего их более 12 типов для применения в различных сферах: от пищевой промышленности и биофармацевтики до обезвоживания нефтешламов или отвальных хвостов горнодобывающей промышленности). Использование декантерной центрифуги Aldec G3 обеспечивает максимальное сокращение совокупных издержек на обезвоживание осадков сточных вод. Описаны виды ремонтных работ декантерных центрифуг, осуществляемые в единственном на территории России сертифицированном по стандартам ISO сервисном центре Альфа Лаваль.

Faecal sludge dewatering is often a necessary step in many treatment and reuse processes, and it can decrease costs of transporting large volumes of high water content sludge. Common dewatering methods such as settling-thickening tanks and drying beds are not feasible in space-constrained areas such as urban informal settlements, therefore innovative dewatering methods are needed. This study evaluated permeable membranes as a dewatering method for a transfer station operated by Sanergy in Nairobi, Kenya. The objective was to determine if membranes could provide a sustainable and economically-feasible dewatering method within the constraints of Nairobi’s informal settlements by evaluating multiple variables, such as flocculant dosage and initial total solids content, and their relation to faecal sludge dewatering. Experiments were conducted with several membrane types including commercial geotextiles and locally-produced plastic woven bags (gunny sacks). Increasing the flocculant dosage within an optimal range was seen to increase dewatering rates, but had minimal effect on the final dewatered solids content. Sludge with initial total solids contents below 3% was seen to require longer dewatering times to allow for drainage, while sludge above 3% required a minimal drainage period before evaporation began. A settling step proved paramount for sludge with high water content where the supernatant was then decanted prior to dewatering through permeable membranes; however, this may not be recommended in all cases depending on the treatment objectives. Reuse of geotextile membranes may lead to a reduction in dewatering performance, and single-use, locally-produced membranes are a more cost-effective, though operationally intensive, option.

Coagulants and flocculants have been widely used in various applications, especially in wastewater treatment and sludge dewatering, which result in their high accumulation in waste-activated sludge (WAS). In the past years, the fate and impact of coagulants/flocculants in WAS anaerobic treatment have been extensively studied. Many efforts have been made to explore their effects on WAS anaerobic treatment performance, reveal the underlying mechanism, and establish regulation methods. To date, however, no efforts have systematically summarized or critically considered the fate and impact of coagulants/flocculants in WAS anaerobic treatment systems. In this work, the use and distribution of flocculants/coagulants in wastewater collection and treatment system are summarized, the presence of coagulants/flocculants promoted the formation of large sludge floc, increased the mass transfer resistance of WAS anaerobic treatment, hindered the release of organics from the solid sludge to the liquid phase, and inhibited some related bioprocesses, thus reducing the WAS anaerobic treatment efficiency. In addition, the fates of coagulants/flocculants in anaerobic systems are also clarified, and the regulation strategies (e.g., pH adjustment) to mitigate the harmful effects are analyzed. Herein, the opportunities and challenges of coagulants/flocculants applied in wastewater and sludge treatment systems are rethought, and further research perspectives are put forward.

Sludge dewatering is the fundamental process of sludge treatment. Environmentally friendly and efficient sludge conditioning methods are the premises of sludge to achieve dehydration reduction and resource utilization. In response to sewage plant sludge dehydration, fly ash (FA), polymerized aluminum chloride (PAC), and polymer sulfate (PFS) were studied separately to determine their sludge dehydration performance, and the effects of these three conditioner composite regulations on sludge dehydration properties were studied. Compared to the sludge treated only with conditioner, the average particle size of floc increased and the organic matter content in the filtrate decreased. The sludge dewatering efficiency after the conditioning effect is better than that after conditioning a single conditioner. After PFS conditioning with fly ash, the water content and specific resistance (SRF) of the sludge cake can be reduced to 76.39% and 6.63 × 1010 m/kg, respectively. The moisture content and specific resistance (SRF) of the sludge cake can be reduced to 76.10% and 6.91 × 1010 m/kg, respectively. The pH of the sludge and filtrate changed slightly after PAC conditioning with fly ash coupling. These results indicate that fly-ash coupled with PAC and fly-ash coupled with PFS are expected to become a novel and effective environmental protection combined conditioning method for sludge dewatering.

Much research has been conducted to improve sludge dewaterability and reveal its dewatering process. However, to date, two key issues remain unsolved: (1) the difficulty of dewatering sludge and (2...

At present, the sludge production has increased sharply, and sludge treatment remains a serious problem. Rapid sludge dewatering is the key problem of sludge treatment, and the main approach for reducing the cost of the sludge treatment is to reduce the cost of sludge dewatering. In this paper, two groups of sludge dewatering tests were carried out using homemade instruments and equipment. One group was conducted without rice straw, and the other group was conducted with rice straw. The relevant mechanism was analyzed, and the results indicate that sludge dewatering with a vacuum negative pressure load of the full section at the bottom is better than mechanical sludge dewatering. The sludge dewatering effect with rice straw is better than that without rice straw. Additionally, the vacuum degree inside the sludge decreased sharply. The pore water pressure slowly dissipates during the early and late stages and quickly during the middle stage. Sludge pore water seepage does not obey Darcy’s law, and sludge dewatering is intermittent.

The effects of rice husk flour (RHF), rice husk biochar (RHB), and rice husk-sludge cake biochar (RH-SCB, expresses sludge cake biochar deriving from a sludge that has been previously conditioned with rice husk) used as physical conditioners on sludge dewaterability were compared. The effects of characteristics of physical conditioners on sludge compressibility and zeta potential were analyzed. The optimal rice husk-based powder was RH-SCB, which presented the highest net sludge solid yield (YN, expresses the dry mass flow by filtration) at 20.39 kg/(m2 h) for 70% dry sludge (DS). Characterization analysis indicates that the hardness and surface Fe content of powders which could influence the compressibility coefficient of sludge cake and sludge zeta potential were the major factors influencing sludge dewaterability. The comparison of feasibility and economic analysis showed that adding RH-SCB improves the quality of the sludge filtrate and reduces the pollution potential of conditioned sludge (the ratio of secondary and primary (RSP) of Cu, Zn, Cd reduces from 43.05, 144.00, 7.25 to 7.89, 14.63, 4.27, respectively), and the costs of using RH-SCB were the lowest (at 88.4% lower than that of the raw sludge). Therefore, it is feasible to use RH-SCB to improve sludge dewaterability.

A combination of hydrothermal treatment and FeSO4/Ca(ClO)2 oxidation was developed in our previous work and was proved to be significantly useful for improving the sludge dewaterability. The dewatering mechanism of the sludge after the combined treatment of hydrothermal treatment and FeSO4·7H2O/Ca(ClO)2 was obtained for the first time based on the moisture distribution analysis. Moreover, the noncovalent interaction between the hydrophilic sites of sludge EPS in sludge and water molecules was studied for the first time by using density functional theory. The electrostatic potentials of three representative EPS molecules, that is, dextran, poly-gamma-glutamate, and poly-l-lysine, were calculated and analyzed. AIM and RDG of the representative EPS·water complex models were calculated to study the noncovalent interaction mechanism. The moisture distribution and noncovalent interactions analyzed in this paper will provide information for improving sludge dewatering performance.

Dewatering pre-treatment, chemical conditions for sludge are practical approaches to advance the performance of sludge-dewatering, hence lessen the cost of sludge transportation and treatment. Cationic polymeric flocculants are used as chemical regulators because of their excellent performance and economic advantages. Current research focused on synthesizing flocculants Polyacrylamide, methacrylamido propyl trimethyl ammonium chloride, Lauryl acrylate, and Poly Acrylamide, methacrylamido propyl trimethyl ammonium chloride (PAT). The synthesis was achieved by ultraviolet initiated (UV-initiated)-induced polymerization technique. The chemical composition of the samples was investigated using Fourier transform infrared (FTIR) spectroscopy and hydrogen nuclear magnetic resonance (1H NMR). This study also evaluated the thermal stability of PATL and PAT by using thermogravimetric/differential scanning calorimetry (TGA). Moreover, the results of scanning electron microscopy (SEM) confirmed the strong floc structure has the ability to form porous and channel construction, making the filter cake a constructive drainage way. It is able to be used for water release and therefore helps to improve dehydration capacity. The hydrophobic flocculants properties in water were investigated by initiator concentration, initiation time and urea concentration. The experimental results confirmed that the optimal values for preparation of PATL were composed of initiator concentration of 0.4 wt.‰, urea level of 1.2 wt.‰; molar ratio of MPTAC to AM (5:95), irradiation time of 60 min and flocculants intrinsic viscosity of 1350 mL/g. Furthermore, it was found that PATL had stronger hydrophobic collaboration with satisfactory water solubility and also improved the dewatering performance. Sludge dewatering experiments confirmed that filter cake moisture content (FCMC) and specific resistance to filtration (SRF) for PATL flocculants reached to 65% and 6 × 1012 m/kg, respectively at the optimal dosage of dry solids about 30 mg · L–1 of sludge, exhibiting better performance than the conventional cationic flocculants (PAT).

Cellulose filter aid (CFA), a skeleton builder, has been studied for sludge conditioning at laboratory scale because of its function in reducing compressibility of sludge cake. However, there are few practical applications of CFA at the pilot and factory scales. In this study, we combined CFA with an advanced sludge dewatering technology, in practical applications. For jar test, the optimum CFA dose was 3 wt.% dry solid (DS); furthermore, the combination of CFA with polyaluminum chloride (PAC) and polyacrylamide (PAM) resulted in the lowest moisture content (73.92%) and the highest calorific value (13,628 kJ/kg) of the sludge cake. In the pilot test, the 5 wt.% DS of the CFA resulted in the optimal sludge feeding amount. In the factory test, the optimal CFA dose was further increased to 10%, and the amount of sludge feeding in a single batch was 20.5% higher than that without CFA. The optimal dose of CFA in the jar-pilot-factory test increased, which may occur because the CFA more easily penetrated the cake and performed better in building the skeleton when the sludge cake was thin. This study could provide a reference for the application of CFA and other skeleton builders in sludge dewatering and drying. PRACTITIONER POINTS: An advanced sludge treatment process-low-temperature vacuum dewatering and drying was tested. Cellulose filter aid showed good effect in jar test, pilot test, and factory test. When the scale of the experiment was from jar to factory, the optimal dosage of the cellulose filter aid was magnified. The amplification phenomenon of optimal dosage was related to the distribution pattern of cellulose filter aid in different thickness mud cakes.

Acrylamide (AM) monomer is one of the harmful type substance, are commonly using to produce polyacrylamide (PAMs) flocculants for water treatment. Because of incomplete polymerization, the molecules of AM monomers also in exit marketable polymers. Therefore, discharge of AM from the usage of PAM based polymers flocculants in to environment. Currently study focus on, the AM leaching behaviour (emulsion and powder) polymer produced by two different production processes was studied with WTP sludge dewatering as the research object. The flocculants type's effects, Concentration of sludge and dosage on the discharge of AM residual monomer in sludge dewatering effluent were studied. The powder form flocculants results show, the regardless of the flocculants concentration and sludge concentration, the leaching concentration is not significant, but in the emulsion flocculants, the leaching concentration changes significantly. The Monomers of residual acrylamide be absorbed on the surface of sludge. Sludge concentration plays an active role in improving dehydration efficiency. Considering the trade-off between emulsion and powder polymer, the results of this study are related to the water treatment process.

Review Sludge Treatment Reed Beds (STRBs) have been used worldwide over the past few decades. This review aims to overarchingly identify and appraise the currently available knowledge of STRB technology and discern climatic patterns through Meta-Analysis (MA). We systematically searched Google Scholar, Scopus, and Web of Science databases (up to Dec 2021) via a combination of keywords to identify English-language studies published in peer-reviewed journals. Of 142 potential articles, 73 studies met the present review objectives and inclusion criteria. Four STRB classifications including typical STRB, earthworm STRB, Sludge Treatment Electro Wetland (STEW), and earthworm STEW were found since 1990. The data and information on STRBs' configuration, operational parameters in terms of location, type of sewage sludge, study scale, Sludge Loading Rate (SLR), Dry Solid (DS), the proportion of Volatile Solid to DS (VS/DS), and their association with the feeding and resting modes were extracted fromthe selected articles. The analysis was focused on the interconnections between operational parameters and system efficiency for Temperate type 1 (low intensity of solar radiation), Temperate type 2 (high intensity of solar radiation), and Tropical climates. Based on MA, we found the average SLRs of 50, 70, and 101 Kg.DM.m−2.year−1 for Temperate type 1, Temperate type 2, and Tropical climates respectively, and DS during the feeding of 33 %, 35 %, and 40 %. A qualitative comparison of Arid and Polar climates was also performed given the reduced number of studies available in these climates. The volume of the sludge reduced was 60 % higher and the height of accumulated sludge was annually 2 cm in the earthworm STRBs, and STEWs compared to typical STRBs, which was 6 cm annually in Tropical climates. Correlation analysis, media characterization, list of plant species, and the removal efficiency of STRBs in the residual sludge and leachate are mentioned as well info:eu-repo/semantics/publishedVersion

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do Paraná The world is facing a water crisis because the population is growing, people are using more water, and more wastewater is being produced. The increase in wastewater production means that there needs to be more treatment of this waste. This treatment generates sludge, which is dangerous for the environment and for people's health. Dewatering sludge is an important part of treating it, which can be done better by treating this with coagulants. The seeds of Moringa oleifera, or MO, have the potential to be employed as a coagulant, making them a less expensive and environmentally friendly alternative. MO seeds were shelled, crushed, and their oil content removed before being dried at 45°C for 24 hours to extract the active coagulant. The active coagulant components were extracted by mixing the processed seed with a NaCl solution (10 % m/v), being the 1.0 M concentration found to be optimal. The extraction was done in two ways: one with ordinary agitation (MOC) and the other with ultrasound assistance (MOC-U), both of which were filtered to remove undissolved particles. The sludge was conditioned using a jar test with fixed rapid and slow mix configurations and different coagulant dosages. The dewatering trials were carried out for 24 hours in dewatering columns with varying sludge height (10, 20 and 40 cm) and a fixed 10 cm filtering medium of inert material. TS, volume of filtered removed, COD, pH, and turbidity were the parameters analyzed. For all experiments, the MOC coagulant increased the sludge's dewatering capacities, however the MOC-U coagulant had most of the outcomes below the control experiment results. The MOC coagulant produced the most satisfactory results in studies with an initial sludge height of 10 cm. The best TS and filtrated removal values were 18.6% and 87 mL, respectively. COD values have been demonstrated to increase as coagulant dosage is increased. In addition, the initial sludge height has been shown to have a negative impact on the sludge's dewatering abilities. To optimize the extraction process employing ultrasound technology, more research is needed. Further testing in the conditioning phase is also required to enhance the sludge dewatering process. O mundo enfrenta uma crise de água porque a população continua a crescer, as pessoas estão a utilizar mais água, e a produzir mais água residual. O aumento da produção de águas residuais torna necessário haver mais tratamento destes resíduos. Este tratamento gera lamas, que são perigosas para o ambiente e para a saúde das pessoas. A desidratação das lamas são uma parte importante do seu tratamento, o que pode ser melhorado tratando-as com coagulantes. As sementes de Moringa oleifera, ou MO, possuem potencial para serem empregadas como coagulante, tornando-as uma alternativa menos custosa e ecologicamente correta. As sementes de MO foram descascadas, trituradas, e o seu teor de óleo foi removido antes de serem secas a 45°C durante 24 horas para extrair o coagulante activo. Os componentes do coagulante activo foram extraídos misturando a semente processada com uma solução de NaCl (10 % m/v), sendo a concentração de 1.0 M óptima. A extração foi feita de duas maneiras: uma com agitação normal (MOC) e outra com assistência de ultra-sons (MOC-U), ambas filtradas para remover partículas não dissolvidas. A lama foi condicionada utilizando um teste em frasco com configurações de mistura rápida e lenta fixas e diferentes dosagens de coagulante. Os ensaios de desidratação foram realizados durante 24 horas em colunas de desidratação com altura variável da lama (10, 20 e 40 cm) e um meio filtrante fixo de 10 cm de material inerte. TS, volume de filtrado removido, COD, pH e turbidez foram os parâmetros analisados. Para todas as experiências, o coagulante MOC aumentou a capacidade de desidratação da lama, contudo o coagulante MOC-U teve a maioria dos resultados abaixo dos resultados da experiência de controlo. O coagulante MOC produziu os resultados mais satisfatórios em estudos com uma altura inicial de lodo de 10 cm. Os melhores valores de TS e de remoção de filtrado foram de 18.6% e 87 mL, respectivamente. Foi demonstrado que os valores de COD aumentam à medida que a dosagem do coagulante é aumentada. Além disso, foi demonstrado que a altura inicial da lama tem um impacto negativo nas capacidades de desidratação da lama. Para optimizar o processo de extração empregando tecnologia de ultra-sons, é necessário realizar nova investigações. São também necessários mais testes na fase de condicionamento para melhorar o processo de desidratação das lamas.

Flocculation and dewatering of anaerobically digested sludge is known to be a major cost factor in the economy of wastewater treatment plants. Hence, several endeavors have been underway in search of affordable and effective alternatives. This study focuses on the effects of different metal cations, including FeCl3, CaCl2 and MgSO4, on the dewaterability of digested sludge. The effects of these metal flocculants were also investigated in the presence of co-polymers and surfactants, which can be considered the novelty of this study. The polymers and surfactants investigated in this study were emulsion polymer, CTAB and SDS. Sampling and characterization of digested sludge was conducted, and total solid (TS), volatile solid (VS), dewaterability in capillary suction time (CST), total dissolved solids (TDS), chemical oxygen demand (COD), pH and conductivity of the unconditioned digested sludge samples were determined. The dewaterability of FeCl3, CaCl2 and MgSO4 conditioned digested sludge samples were compared, and MgSO4 conditioned digested sludge showed better dewaterability compared to the other two metal conditioning agents at a pH of 6.8. The dewaterability was further improved by the addition of emulsion polymer (EMA 8854), cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). Fe Cl3 was found to perform better under an acidic pH of around 3. The dual conditioning using polymer and CTAB resulted in better dewaterability, with CaCl2 as metal conditioning agent. Moreover, the effects of pH, metal dose and polymer dose on the dewaterability of digested sludge were also investigated. The effects of metal and polymer conditioning on the particle size of the sludge flocs was also investigated. Optimum dewatering performance was achieved for metal doses of 0.16 v/v, 0.075 v/v and 0.16 v/v for FeCl3, CaCl2 and MgSO4, respectively, and a corresponding CTAB dose of 0.1 v/v and EMA dose of 15 kg/TDS were found to be the optimum. SDS as a polymer conditioning agent resulted in the deterioration of dewatering performance.

Mine water usually contains heavy metals and other inorganic and organic pollutants that contaminate water bodies. Reverse osmosis (RO) techniques are capable of producing purified water that meets discharge regulations. However, the problem of RO concentrate disposal and utilization is still not solved. The well-known zero liquid discharge (ZLD) process provides total concentrate utilization at the power industries but seems unreasonably expensive for the treatment of large amounts of mine water due to required chemical softening and the evaporation of concentrate. In the present article, a new approach to increase the recovery of reverse osmosis and to avoid high operational costs is demonstrated and discussed. The new technique involves radical RO concentrate flow reduction and withdrawal, together with dewatered sludge. The idea to “hide” concentrate in dewatered sludge is proposed and demonstrated during experiments. The article demonstrates results of the conducted experimental program aimed at reduction of volumes of all liquid wastes produced during mine water treatment using a new approach to concentrate it with a cascade of nanofiltration membranes and to reach a TDS value of 110–120 g per liter. The obtained concentrate is mixed with the wet sludge, which is further dewatered and withdrawn together with the dewatered sludge. Experiments are conducted that demonstrate a reduction in calcium in the concentrate due to deposition of calcium carbonate on the “seed crystals” in the circulation mode. Another distinguishing feature of the new technique is the separation of concentrate into two streams containing high concentrations of monovalent ions (sodium and ammonium chlorides) and divalent ions (calcium, magnesium and copper sulphates). Flow diagrams of the processes are presented to demonstrate the water treatment technique used to produce deionized water and two types of sludges: sludge after clarification and sludge after calcium carbonate deposition.

A new technology is described that enables us to completely exclude liquid discharges during production of drinking water from surface sources. The proposed described technological scheme separates the natural water into a stream of purified drinking water and dewatered sludge. The sludge moisture has a value of 80 percent. The experimental program is described to treat the natural water with nanofiltration membranes and to produce a drinking-quality water with recovery value of 0.99 and higher. Concentrate of membrane plant is mixed with the wet sludge and the reject effluent after sludge dewatering is again treated by reverse osmosis membranes and returned back to the sludge thickening tank. Results of experiments to treat reject water after sludge dewatering are presented. The use of nanofiltration membranes provides reduction in the Total Dissolved Solids content (TDS), aluminum, color and oxidation to meet drinking water standards. Experimental plots are presented that can be used to select membrane characteristics and to predict product water chemical composition at each stage of the membrane treatment scheme. Concentrate of membrane treatment plant is mixed with the wet sludge in the thickening tank. The sludge, after the thickening tank, is dewatered using either filter-press or centrifugal equipment. The reject (or fugate), after sludge dewatering, is treated by membrane facility to separate it into deionized water stream and concentrate stream. The deionized water can be mixed with the feed water or drinking water and the concentrate stream is returned back to the thickening tank. Thus, the salt balance is maintained in the thickening tank, whereby all dissolved salts and impurities that are rejected by membranes are collected in the thickening tank, and then are withdrawn together with the dewatered sludge. Based on the results of experimental data processing, balance diagrams of the sludge dehydration process with waste water purification at the membrane plant and with the addition of the membrane plant concentrate to the sludge thickener are presented, according to which all contaminants removed by the membranes are removed together with the sludge.

During recent decades the quality of pulp and paper mill sludge has changed. This has awakened the need for an applicable means to observe the sludge dewatering process diversely and accurately. To maximize the solids content and energy efficiency of board mill sludge dewatering, different process monitoring options were studied. Novel methods for monitoring the sludge dewatering operation of a belt filter were tested. Continuous run-time measurements and test response experiments were carried out at a board mill site. IR transmittance measurement through the filter web and sludge mat thickness measurement using a light curtain turned out to be very promising techniques. IR transmittance responded to the polymer content of the sludge without a notable time lag, while the solid content measurement of the filtrate did not give a measurable response.

The effects of lysozyme (LZM) and freeze-thaw conditioning, alone or in combination, on sludge dewatering performance were comparatively investigated. After the optimization of the dewatering conditions using response surface methodology (RSM), the co-conditioning exhibited obvious superiority to the separate conditioning in improving the dewaterability of municipal sludge, with the capillary suction time (CST) and the water content (W) of the dewatered sludge reduced to 12 ± 0.5 s and 52.0% ± 0.4% from 61.8 s and 73.0%, respectively. The co-conditioning appeared not only to destroy the structure of extracellular polymeric substance (EPS) and microbial cell wall by virtue of enzymatic conditioning, but it formed larger particles and compact sludge floc structure with the help of freeze-thaw conditioning. Additionally, the bound water content of sludge decreased by 47.5% after co-conditioning, consistent with the enhancement in sludge dewaterability. All the results showed that LZM in combination with freeze-thaw conditioning had a great potential in sludge reduction, providing more opportunity of resource utilization for the dewatered sludge.

Quaternized lignin-based flocculant (QL) was prepared by a single-step reaction of an extracted lignin (EL) derived from oil palm empty fruit bunches (OPEFB) with 3-chloro-2-hydroxypropyl trimethyl...

Urbanisation is putting enormous pressure on wastewater treatment plant facilities. Optimising the liquid and sludge process streams in existing plants is one way of prolonging the life span of such installations. Many Wastewater treatment plants (WWTP) have sludge dewatering installations where treated wastewater sludge is dewatered using belt filter presses amongst others, before final disposal. One of the most expensive inputs in these plants is the polymers used as flocculants. Controlling the optimum dosing in the dewatering process cannot currently be done in real-time. It has been shown that huge savings can be made by optimising the dosing rates of polymers based on the sludge rheology. An Ultrasound Velocity Profiling (UVP) and pressure drop (PD) measurement system was specially designed and commissioned for a WWTP. The system was installed in a WWTP to measure the rheological properties of sludge in-line and in real-time prior to mechanical dewatering using a belt filter press. This non-invasive in-line system was able to accurately measure the rheological parameters in real-time in a 100 mm stainless pipe. It was shown for the first time what the maximum in-line yield stress is that is required for optimum dewatering based on a relationship determined between the yield stress and the total suspended solids in the filtrate exiting the belt filter press.

BACKGROUND: Extracellular polymeric substances (EPS) play an important role in sludge dewatering. Inorganic coagulants treatment has been widely used to remove the EPS and improve sludge dewaterability. This research evaluates whether there are advantages of selecting one of two chemical coagulation pretreatments, conventional aluminium or iron salts, over the other to enhance sludge dewaterability. The study traced variations in EPS characteristics to understand the mechanisms of sludge dewaterability. RESULTS: The results showed that iron coagulants improved dewatering more than aluminium coagulants, by approximately 28.66%. The improved sludge dewaterability was further confirmed in pilot‐scale experiments. Compared with aluminium salts conditioning, iron salts were better able to neutralize stronger charge, formed smaller and more compact flocs, and had a stronger acidification effect. Sludge dewaterability was significantly related to EPS concentrations (i.e. the protein and polysaccharides), EPS composition (i.e. tyrosine/tryptophan amino acid, tyrosine/tryptophan protein, and polysaccharide), and functional groups (i.e. random coil, β‐sheet, and Nₚᵣ) in the loosely bound EPS (LB‐EPS). A two‐step mechanism was proposed for the iron conditioning process. Moreover, the economic analysis shows iron treatment was more economical than that of aluminium. CONCLUSION: Iron salts conditioning removed more LB‐EPS than aluminium salts, thus more significantly improving sludge dewaterability. © 2018 Society of Chemical Industry

The minimization of sludge produced by municipal wastewater treatment plants (MWWTPs) is critical as its handling accounts for approximately 50% of the total operating cost. The challenges in predicting dewatering performance can be overcome by optimizing the sludge treatment process, especially conditioning and dewatering. This study aimed to investigate sludge dewaterability at four different MWWTPs, using a gravity drainage test unit and a bench-scale press. The effect of differently treated effluent used as a solvent to mix the flocculation polymers was observed during dewatering. The membrane bioreactor (MBR) treated effluent yielded the highest filtrate volume in the lowest amount of time, with the least polymer flocculant dosage. The Box Behnken Design model fitted the data and proved a relationship between polymer dosage, cake solids concentration, and cake height during the bench-scale press tests. Highlights The type of water used for polymer flocculant dissolution has, to an extent, a considerable impact on the gravity drainage of the sludge.; Increasing polymer flocculant dosing is not directly proportional to the cake height and cake dryness.; Significant correlation between sludge characteristics (e.g. feed solids) and the cake formed.

Mechanical dewatering is a key process in the management of sewage sludge. However, the drainage efficiency depends on a number of factors, from the type and dose of the conditioning agent to the parameters of the drainage device. The selection of appropriate methods and parameters of conditioning and dewatering of sewage sludge is the task of laboratory work. This work can be accelerated through the use of artificial neural network (ANNs). The paper discusses the possibilities of using ANNs in predicting the dewatering efficiency of physically conditioned sludge. The input variables were only four parameters characterizing the conditioning methods and the dewatering method by centrifugation. These were the dose of the sludge skeleton builders (cement, gypsum, fly ash, and liquid glass), sonication parameters (sonication amplitude and time), and relative centrifugal force. Dewatering efficiency parameters such as sludge hydration and separation factor were output variables. Due to the nature of the research problem, two nonlinear networks were selected: a multilayer perceptron and a radial neural network. Based on the results of the prediction of artificial neural networks, it was found that these networks can be used to forecast the effectiveness of municipal sludge dewatering. The prediction error did not exceed 1.0% of the real value. ANN can therefore be useful in optimizing the dewatering process. In the case of the conducted research, it was the optimization of the sludge dewatering efficiency as a function of the type and parameters of conditioning factors. Therefore, it is possible to predict the dewatering efficiency of sludge that has not been tested in the laboratory, for example, with the use of other doses of physical conditioner. However, the condition for correct prediction and optimization was the use of a large dataset in the neural network training process.

Sludge dewatering is a prerequisite for the subsequent utilization of sludge. However, the existing mechanical dewatering cannot achieve satisfactory water content (< 60%). Herein, pressure and electric dewatering in alternate operation (P/EDWalt) was proposed to improve dewatering efficiency. Compared with conventional simultaneous mode, P/EDWalt performed better in sludge dewatering. Its optimal dewatering conditions were voltage of 30 V for 20 min in two electric dewaterings, and pressure of 0.04, 0.07 and 0.10 MPa in three pressure dewaterings. Such conditions, the water content of sludge was reduced from 83.7% to 53.3%, the dewatering efficiency was 36.3%, and the energy consumption was 0.138 kWh/kgtotal removed water. These phenomena such as electroosmosis, the ohmic heating and electrophoresis facilitated the removal of water in sludge, and the dewatered sludge has good reusability in incineration, landfill and agriculture. Therefore, P/EDWalt could serve as a promising method for the sludge dewatering.

Sewage sludge dewatering and drying is one of the major challenges in the current wastewater treatment systems. The current dewatering methods in centralized wastewater treatment plants whether using frame or belt filter press or centrifuges are energy intensive and requires up to 50% of the cost of wastewater treatment. The moisture content of the sludge cake after dewatering is also a key factor in determining the efficiency of sludge handling and utilization including energy efficiency and pollutant emission. This is even more challenging for decentralized sludge management aiming at resource recovery and local resource utilization from the perspective of circular economy. To overcome these challenges, an experiment was designed to develop an alternative sludge dewatering and drying method for decentralized wastewater treatment systems and local production of sludge-based biochar. Raw sludge was collected from Frogn Renseanlegg, a wastewater treatment plant in Drøbak, in Viken county of Norway. The sludge was filtered in the laboratory using a solid-liquid separation system containing a 200µm and 100µm mesh integrated with sand filtration to remove free water through gravity to produce a sludge cake. The effect of different percentages of Wood pellets (WP), Spent Coffee Grounds (SCG) and different mixture of the two as bulking agents for deep-dewatering (removal of tightly bound water) was investigated without energy input. The percentages of Wood Pellets (WP) and Spent Coffee Grounds (SCG), varied from 0% (control) to 20% by weight of the raw sludge. The moisture content of the mixture was determined at an average temperature of 17°C after 1, 24, 48, 72 and 96 hr. In the experiment, sludge with addition of 5% SCG, 10% SCG and 20% SCG had an average moisture content of 71.1%, 66.0% and 46.0%, respectively, after 96 hours. For 5% WP, 10% WP and 20% WP, the average moisture content after 96 hours were 70.3%, 55.9% and 45.6%. Adding a small amount of superabsorbent facilitated reduction of the amounts of SCG and WP and achieved a moisture content reduction down to 9.0% after 72 hours. The removal of tightly bound sludge water and fast drying in sludge conditioned with WP and SCG may be mainly explained by absorption by the amendment and subsequently a better porosity and larger surface area for evaporation. M-MINA

In an activated sludge system, the high hydrophilicity of extracellular polymeric substances (EPS) and the high compressibility of sludge greatly hinder sludge dewatering. A new method for improving the dehydration of waste activated sludge was explored by using iron powder activated peroxomonosulfate combined with waste straw (Fe0+PMS + WS). Specific resistance to filtration (SRF) and water content (Wc) were used to characterize the dewatering performance of sludge. Under the optimal measurement, Wc and SRF were significantly reduced. To reveal the synergistic effect of this joint treatment, zeta potential, particle size distribution, three-dimension excitation emission matrix (3D-EEM) fluorescence spectroscopy, bound water content analysis, and scanning electron microscopy (SEM) were used to investigate the mechanism of sludge dewatering. Results showed that the tightly bound EPS (TB-EPS) was oxidized by sulfate radicals (SO4−∙) to loose bound EPS (LB-EPS) and soluble EPS(S-EPS). SEM analysis displayed that the Fe0+PMS + WS combination regulated the formation of a more porous sludge filter cake structure. In addition, the low calorific value of the dewatered sludge after 12 h in open air was significantly increased, and the Wc of the dewatered sludge cake was reduced to 25%. These parameters were beneficial to the subsequent disposal of sludge.

Дисертація на здобуття наукового ступеня доктора філософії за спеціальністю 101 – Екологія (10 – Природничі науки). – Національний технічний університет "Харківський політехнічний інститут" Міністерства освіти і науки України, м. Харків, 2021. Роботу виконано на кафедрі хімічної техніки та промислової екології Національного технічного університету "Харківський політехнічний інститут" Міністерства освіти і науки України. Об’єктом дослідження є процеси очищення шламів мокрої газоочистки металургійного виробництва на основі флокуляції та седиментації завислих часток. Предмет досліджень – рішення питань екологічної безпеки при очищенні та зневодненні шламів металургійних підприємств на основі запропонованих методик пошуку оптимальних умов флокуляції і збереження міцності флокул при їх транспортуванні для агрегатоутворення твердої фази. Дисертаційне дослідження присвячене розв’язанню задач екобезпеки при пошуку оптимальних умов очищення та зневоднення тонкодисперсних шламів металургійних виробництв з використанням інноваційного рішення щодо процесу агрегатоутворення завислих часток шляхом флокуляції твердої фази. У вступі обґрунтовано наукову актуальність дисертаційної роботи, сформульовано мету і задачі, визначено об’єкт, предмет і методи дослідження, показано зв’язок роботи з науковими темами, сформульовано наукову новизну та наведено практичне значення отриманих результатів. Перший розділ присвячено аналізу та систематизації наукових і статистичних даних, отриманих з джерел інформації, щодо впливу металургійного виробництва на екологічний стан навколишнього середовища, сучасних методів очищення стічних вод і шламів, процесів зневоднення та утилізації осадів підприємств металургійної галузі. Визначені основні тенденції з пошуку шляхів розв’язання задач екологічної безпеки на металургійних підприємствах відповідно до методів інтенсифікації процесу очищення стічних вод і шламів при використанні флокулянтів, для яких позначені оптимальні умови використання для підвищення рівня безпечності та екологічної якості на виробництві. На підставі аналізу обґрунтовано наукові задачі дисертаційного дослідження. У другому розділі наведено характеристику засобів та методів дослідження технологічних рішень для підвищення екологічної ефективності очищення шламів на основі флокуляції. Лабораторні досліди з вивчення флокуляції і особливостей змін швидкості осідання флокул, визначення гідродинамічного впливу на флокули, встановлення складу та властивостей речовин здійснювалось за допомогою об’ємних, вагових та фізико-хімічних методів дослідження за стандартними методиками. Експериментальні роботи з модельними шламами проводилися в лабораторії кафедри хімічної техніки та промислової екології НТУ "ХПІ" і відокремленій аналітичній лабораторії ТОВ "НТЦ "Екомаш". Третій розділ присвячений результатам експериментальних дослідів флокуляції тонкодисперсних шламів, проведених в лабораторних умовах з модельними суспензіями і в промислових умовах на реальних стічних водах металургійних виробництв на модулі очищення стічних вод. У розділі досліджені питання екологічної безпеки при отриманні металонаповнених композитів з використанням відходів металургійного виробництва. За експериментальними дослідами отримані такі результати: – досліджено вплив концентрації твердої фази модельних шламів мокрої очистки газу і витрати флокулянту на зміни величини швидкості осідання твердої фази і міцності флокул; флокуляція здійснюється найбільш ефективно, а саме для дослідженого виду шламу вона склала 8–12 г/л; – установлено, що зміни швидкості руху рідини додатково на і понад 1–1,5 м/с призводить до значного руйнування флокул, що є більш дієвим за тривалість перебігу процесу за висновками дослідження гідромеханічного впливу на агрегати, руйнуюча дія якого залежить від концентрації твердої фази, часу та інтенсивності перемішування сфлокульованого шламу; – виявлено, що вологість осаду та ефективність затримання твердої фази залежить від міцності флокул перед центрифугою; – встановлена залежність міцності флокул від параметрів агрегатоутврення (концентрації, витрати флокулянта та продуктивності) за результатами дослідження ефективності затримання твердої фази і зневоднення тонкодисперсних шламів металургійного підприємства на модулі очищення і зневоднення шламу; – визначені умови утилізації дрібнодисперсного пилу ливарних виробництв в якості наповнювача композитів холодного затвердіння за результатами дослідження впливу дисперсної твердої фази металевих відходів на міцність та експлуатаційні характеристики металонаповнених епоксидних композитів. У четвертому розділі подані результати статистичної обробки даних експериментів, математичного моделювання процесів очищення й зневоднення шламів та пошуку оптимальних значень параметрів утилізації з урахуванням вимог екологічної безпеки для металургійного виробництва. За отриманими аналітичними даними надані такі висновки: – установлені розрахункові залежності дозволяють визначати кількість флокулянту або швидкість осадження флокул при врахуванні інших чинників, вплив факторів агрегатоутворення на зміну швидкості осідання твердої фази і залишкову міцність флокул після гідродинамічного впливу; – визначені розрахункові залежності для промислового модуля надають можливість оперативно розрахувати концентрацію твердої фази в шламі, кількість флокулянту та швидкість осадження флокул до відстійника та після нього, на основі яких робиться заключення про досягнення певного рівня екологічної ефективності зневоднення осаду у центрифузі та відповідності вимогам екобезпеки при утилізації шламів; – прийнято за оптимальний екобезпечний вміст наповнювача для досліджуваних металонаповнених епоксидних композитів з використанням відходів у концентраційному інтервалі 45–60 % мас. У п’ятому розділі розроблено науково-обгрунтовані рекомендації щодо вибору оптимальних умов проведення процесу очищення та зневоднення шламів металургійних виробництв і надані такі результати. 1. Визначені мінімальні витрати флокулянту шляхом контролю залишкової швидкості осадження флокул перед зневоднюючим устаткуванням відповідно до запропонованих рекомендацій щодо вибору оптимальних технологічних параметрів очищення стічних вод після очищення газів у металургійному виробництві, методики підбору робочих параметрів устаткування, критерію міцності флокул. Встановлено за необхідне підтримувати постійною концентрацію твердої фази у стічній воді, що надходить на очищення, або регулювати витрати флокулянту залежно від концентрації твердої фази в шламі для досягнення необхідного критерію міцності флокул і потрібного рівня екологічної безпечності стічних вод. 2. Розроблена удосконалена схема технологічного рішення очищення стічних вод і зневоднення шламів з урахуванням можливості автоматичного управління процесами для досягнення певного рівня екологічної ефективності утилізації шламів. Thesis for the degree of Doctor of Philosophy in specialty 101 – Ecology (10 – Natural Sciences). – National Technical University "Kharkiv Polytechnic Institute" of the Ministry of Education and Science of Ukraine, Kharkiv, 2021. The work is carried out at the Department of Chemical Engineering and Ecology of the National Technical University "Kharkiv Polytechnic Institute" of the Ministry of Education and Science of Ukraine. The object of the research is the processes of cleaning sludge from wet gas cleaning of metallurgical production based on flocculation and sedimentation of suspended particles. The subject of the research is the solution of environmental safety issues during the purification and dehydration of sludge from metallurgical enterprises based on the proposed methods for finding optimal conditions for flocculation and maintaining the strength of floccules during their transportation for the aggregation of the solid phase The thesis research is devoted to solving environmental safety problems when searching for optimal conditions for cleaning and dewatering fine sludge from metallurgical industries using an innovative solution on the process of aggregation of suspended particles by flocculation of the solid phase. In the introduction, the scientific relevance of the thesis is substantiated, the aim and objectives are formulated, the object, subject and methods of research are determined, the connection of work with scientific topics is shown, the scientific novelty is formulated and the practical significance of the results obtained is given. The first section is devoted to the analysis and systematization of scientific and statistical data obtained from information sources on the impact of metallurgical production on the environment, modern methods of wastewater and sludge treatment, processes of dehydration and disposal of sludge from metallurgical enterprises. The main trends in the search for ways to solve environmental safety problems at metallurgical enterprises in accordance with the methods of intensifying the process of purification of wastewater and sludge using flocculants are determined, for which the optimal conditions of use are indicated to increase the level of environmental safety in production. Based on the analysis, the scientific tasks of the dissertation research are substantiated. The second section describes the means and methods of researching technological solutions to improve the environmental efficiency of sludge treatment based on flocculation. Laboratory experiments to study flocculation and the characteristics of changes in the sedimentation rate of floccules, to determine the hydrodynamic effect on floccules, to establish the composition and properties of substances are carried out using volumetric, weight and physicochemical research methods according to standard techniques. Experimental work with sludge is carried out in the laboratory of the Department of Chemical Engineering and Ecology of NTU "KhPI" and a secluded analytical laboratory of LLC "STC "Ekomash". The third section is devoted to the results of experimental studies of flocculation of fine sludge, carried out in laboratory conditions with model suspensions and in industrial conditions on real waste waters of metallurgical plants for wastewater treatment modules. The section investigates the issues of environmental safety in the production of metal-reinforced composites using metallurgical waste. According to experimental experiments, the following results are obtained: – the influence of the concentration of the solid phase of model sludge of wet gas cleaning and the flow rate of the flocculant on the change in the rate of sedimentation of the solid phase and the mystics of floccules is investigated; – the optimal concentration of the solid phase is established, at which flocculation is carried out most effectively, namely, for the investigated type of sludge, it is 8–12 g/l; – it is found that changes in the speed of fluid movement by more than 1– 1.5 m/s lead to significant destruction of floccules, which is more effective than the duration of the process, according to the conclusion of the study of hydromechanical action on aggregates, the destructive effect of which depends on the concentration of the solid phase, time and intensity of mixing flocculated sludge; – it is found that the moisture content of the sediment and the efficiency of the retention of the solid phase depends on the strength of the floccules before the centrifuge; – the dependence of the strength of floccules on the parameters of the aggregate-setting (concentration, flocculant consumption and productivity) is established based on the results of a study of the efficiency of the retention of the solid phase and dehydration of fine sludge from a metallurgical enterprise for purification and dehydration modules – the conditions for the utilization of fine dust from foundries as a filler for cold-curing composites are determined based on the results of a study of the effect of the dispersed solid phase of metal waste on the strength and performance characteristics of metal-filled epoxy composites. The fourth section presents the results of statistical processing of experimental data, mathematical modeling of sludge treatment and dewatering processes, and the search for optimal values of disposal parameters, taking into account environmental safety requirements for metallurgical production. Based on the analytical data obtained, the following conclusions are obtained: – calculated dependencies are established that make it possible to determine the amount of flocculant or the deposition rate of floccules, taking into account other factors, the influence of aggregation factors on the change in the sedimentation rate of the solid phase and the residual strength of floccules after hydrodynamic action; – calculated dependencies for the industrial module are determined that provide an opportunity to quickly calculate the concentration of the solid phase in the sludge, the amount of flocculant and the sedimentation rate of floccules to the settling tank and after it, on the basis of which a conclusion is made on the achievement of a certain level of environmental efficiency of sludge dewatering in a centrifuge and compliance with environmental safety requirements during disposal sludge; – accepted as the optimal Eco-friendly content of the filler for the investigated metal-based epoxy composites using waste in a concentration range of 45–60 wt%. In the fifth section, scientifically grounded recommendations for the choice of optimal conditions for the process of purification and dehydration of sludge from metallurgical industries are developed and the following conclusions are drawn. 1. The minimum costs of the flocculant are determined by controlling the residual sedimentation rate of floccules before dewatering equipment in accordance with the proposed recommendations for the selection of optimal technological parameters for wastewater treatment after gas purification in metallurgical production, methods for selecting operating parameters of equipment, criteria for floccule strength. It is established that it is necessary to maintain a constant concentration of the solid phase in the wastewater supplied for treatment, or to regulate the flow rate of the flocculant depending on the concentration of the solid phase in the sludge to achieve the required criterion of floccule strength and the required level of environmental safety of wastewater. 2. An improved scheme of technological solutions for wastewater treatment and sludge dewatering is developed, taking into account the possibility of automatic control of processes to achieve a certain level of environmental efficiency of sludge disposal.

High-solid anaerobic digestion (HS-AD) has been applied extensively during the last few decades for treating various organic wastes, such as agricultural wastes, organic fractions of municipal solid wastes, and kitchen wastes. However, the application of HS-AD to the processing of sewage sludge (SS) remains limited, which is largely attributable to its poor process stability and performance. Extensive research has been conducted to attempt to surmount these limitations. In this review, the main factors affecting process stability and performance in the HS-AD of SS are comprehensively reviewed, and the improved methods in current use, such as HS sludge pre-treatment and anaerobic co-digestion with other organic wastes, are summarised. Besides, this paper also discusses the characteristics of substance transformation in the HS-AD of SS with and without thermal pre-treatment. Research has shown that the HS effect is due to the presence of high concentrations of substances that may inhibit the function of anaerobic microorganisms, and that it also results in poor mass transfer, a low diffusion coefficient, and high viscosity. Finally, knowledge gaps in the current research on HS-AD of SS are identified. Based on these, it proposes that future efforts should be devoted to standardising the definition of HS sludge, revealing the law of migration and transformation of pollutants, describing the metabolic pathways by which specific substances are degraded, and establishing accurate mathematical models. Moreover, developing green sludge dewatering agents, obtaining high value-added products, and revealing effects of the above two on HS-AD of SS can also be considered in future.

Due to the environmental risks caused by microplastics, understanding the sources and characteristics of microplastics and cutting off their routes into the environment are crucial. However, so far, studies on microplastics in the landfill leachate system (a major pathway of microplastics into the environment) are still limited, especially for tiny particles

Phosphorus and nutrient recovery from wastewater as mineral salts can support local replenishment of fertilisers and reduce mining, contributing to the circular economy. Wastewater and related streams are rich in nutrients, however; there is need to develop bio-based processes to recover them. This study investigates the fractions of phosphorus (P) used by Brevibacterium antiquum to form struvite biominerals (bio-struvite) in wastewater sludge dewatering liquors. After 72h of incubation, 25.6 mg P/L were recovered as bio-struvite from 12.4 mg P/L organic plus condensed P and 13.2 mg P/L of ortho-phosphate. The potential of sludge dewatering liquors to recover nutrients as struvite was investigated by characterising ten types of sludge liquors (originating from primary, secondary sludge, feed to anaerobic digester and digestate, from 3 types of wastewater treatment plants) for their P fractions together with other parameters relevant for B. antiquum growth. Results indicated that liquors obtained from primary sludge, feed to anaerobic digesters and digestate were the most suitable to produce bio-struvite, as these were found to frequently have a high content of organic and condensed P, between to 276 – 732 mg P/L. Liquors, from all the investigated sites, presented a higher potential for bio-struvite production than with conventional struvite precipitation. This study demonstrated that B. antiquum could convert organic and condensed P into bio-struvite, and this opens up a completely new way to recover forms of phosphorus that are not typically available for nutrient recovery in a single process.

This study investigated digestibility of biological trickling filter (BTF) sludge (in terms of the mass and volume reduction of the sludge) and the effect of anaerobic digestion on sludge d...

This study was undertaken to develops a new sludge dewatering technology based on polyethylene glycol solution dialysis. This method significantly reduced the final water content of sludge when compared to conventional dewatering methods. It was found that when the osmotic pressure difference between the polyethylene glycol solution and the sludge reached 8 MPa, the moisture content in the sludge was reduced to 28.6%, facilitating deep dehydration. To further improve the dehydration effect and explore the technical feasibility of dialysis dehydration, a dehydration experiment was designed using the polyethylene glycol solution dialysis method combined with external pressure. By applying external pressure to the dialysis membranes, the particles in the sludge were compacted, which reduced the internal voids of the sludge and propelled continuous water discharge. The results demonstrated that the dehydration effect was significantly improved when compared to single dialysis. A scanning electron microscope (SEM) was used to observe and quantitatively analyze the microstructure of the sludge before and after dehydration and to compare the variations in sludge microstructure throughout the dehydration process. The relationships between the sludge moisture content and the porosity and pore equivalent diameter were obtained. This demonstrated the effectiveness of the dewatering experiment using sludge dialysis combined with external pressure. This study also investigates the dehydration mechanism of this method during the sludge dehydration process. This study provides a novel solution for sludge volume reduction that can be applied to sewage treatment in the future.

Sludge treatment in wastewater treatment plants are one of the most difficult challenges. The purpose of this study is to determine the effect of ultrasonic waves on soluble chemical oxygen demand (SCOD), temperature and pH of the sludge during improving the sludge dewatering properties. In this research variables include ultrasound density and Time. With the increase of time, the SCOD also increased, which is due to increasing exposure of cells and microorganisms to sonification. This Enhancing Contacts with ultrasound waves leads to increasing cell wall collapse and the withdrawal of intracellular water, proteins and nutrients into the sludge. Also with the increase of ultrasound density, the rate of SCOD increase has raised. This means an increase of SCOD of the sludge and it is due to the higher import of energy and production of nano-bubbles and damage of cells and biological flocs. By increasing the ultrasound density and sonification time, the temperature was significantly increased.

Sludge disposal such as land application is suspected as a significant source of microplastic (MP) pollution in the environment. To examine such a hypothesis, the present study was conducted to investigate the occurrence of MPs in sludge by analyzing 79 sewage sludge samples collected from 28 wastewater treatment plants (WWTPs) in 11 Chinese provinces. MP concentrations in the sludge samples ranged from 1.60–56.4 × 103 particles per kilogram of dry sludge, with an average of 22.7 ± 12.1 × 103 particles per kilogram of dry sludge. Thereinto, the sludge-based MP contents were greater in eastern China than in western China and varied during different months. Their colors and types were mainly white (59.6%) and fibers (63%), respectively. Microscope Fourier Transform infrared spectroscopy revealed that most of MPs belonged to polyolefin, acrylic fibers, polyethylene and polyamide. Some WWTP parameters, such as servicing area, proportion of industrial wastewater, secondary treatment and sludge dewatering may have affected MP concentrations in sludge. Based on the total sludge production in China, the average amount of sludge-based MPs entering into natural environmental was estimated to be 1.56 × 1014 particles per year. The findings confirmed that sewage sludge discharge is an important source of MP pollution in the environment. Further evaluation of the associated environmental hazards with MPs is deemed necessary.

Dewatering and handling of pulp and paper mill sludge is challenging and often comprises more than half of the overall wastewater treatment costs at a mill. Primary sludge is usually more dewaterable than biosludge (waste activated sludge), and the ratio between both types of sludge largely determines the dewaterability of the sludge mix. This study has quantified the benefits of adding primary sludge to biosludge to enhance the dewaterability in terms of cake solids and filtrate/pressate solids content. Furthermore, the effects of the particle size distribution and the monovalent to divalent cation ratio of the various types of sludge were investigated. Biosludge and three types of primary sludge from a Canadian pulp and paper mill were mixed at various ratios and tested for dewaterability using a Crown Press®, a bench-scale device which simulates industrial belt press dewatering. Results show that after addition of primary sludge at up to 40% mass proportion (dry solids basis) the dewatered cake solids content increased substantially, from 10.4% to 18.7–19.9%, depending on the type of primary sludge added. Further addition of primary sludge led to comparably only small improvements. Primary sludge addition also resulted in decreased total suspended solids (TSS) concentrations in the combined gravity filtrate / Crown Press pressate. Primary sludge content of only 10% in the sludge mix was sufficient to decrease the TSS concentration from 1.8 g/L to 0.2 – 0.4 g/L. The study shows that only less than half of the sludge mix needs to consist of primary sludge, in order to achieve adequate dewaterability. This opens up the possibility of retaining more primary fiber within the pulping process, without compromising downstream sludge dewatering.

Electro-dewatering (ED) pretreatment could improve sludge dewatering performance and remove heavy metal, but the effect of ED pretreatment on nitrous oxide (N2O) emission and related functional genes in sludge composting process is still unknown, which was firstly investigated in this study. The results revealed that ED pretreatment changed the physicochemical characteristics of sludge and impacted N2O related functional genes, resulting in the reduction of cumulative N2O emission by 77.04% during 60 days composting. The higher pH and NH4+-N, but lower moisture, ORP and NO2−-N emerged in the composting of ED sludge compared to mechanical dewatering (MD) sludge. Furthermore, ED pretreatment reduced amoA, hao, narG, nirK and nosZ in ED sludge on Day-10 and Day-60 of composting. It was found that nirK reduction was the major factor impacting N2O generation in the initial composting of ED sludge, and the decline of amoA restricted N2O production in the curing period.

© 2018 Elsevier Ltd. All rights reserved. Understanding the interactions between sludge particles and polymers during sludge dewatering is necessary to: firstly, maximize dewatered cake solids content; and secondly, minimize polymer demand. In this study, two scientific methodologies, namely the 'y-intercept' concept and Higgins modified centrifugal technique (Higgins MCT) were used to identify the optimum polymer demand and type for effective conditioning and dewatering. Results from the 'y-intercept' concept show that a large amount of polymer required during conditioning of anaerobically digested sludge (ADS) is mainly due to neutralization of soluble biopolymers. In contrast, conditioning of aerobically digested sludge (AEDS) and waste activated sludge (WAS) is mostly controlled by a polymer bridging mechanism. The results indicated that, in order to achieve maximum dewatering performance with minimum conditioning polymer requirement, high charge density polymers are suitable for ADS while branched (or cross-linked) polymers can be used for AEDS and WAS. The new lab-scale technique, Higgins MCT, was successfully implemented for measuring cake solids content achievable by centrifuge and determining the optimum polymer demand (OPD). The Higgins MCT also helped to understand the relationship between digestion, conditioning and dewatering.

The present paper aims to introduce a novel and environment-friendly sludge dewatering method based on the osmotic technique, and to examine the efficiency of this method from macro- and micro-points of view. Intact sample, taken from the primary settler of a local wastewater treatment plant in Guangzhou (China), was firstly dewatered by mechanical methods (i.e. vacuum filtration and centrifugation), then by the osmotic technique. Macroscopic experimental results show that: the vacuum filtration and centrifugation can only dewater the sludge from 94.5 to 78.3% and to 78.8%, respectively, whereas, using the osmotic technique, water content of the sludge can be decreased to 44.2% in 12 h and to 35.9% in about two days. The micro-structure, obtained by scanning electron microscope (SEM), shows that: the sludge samples after vacuum filtration and centrifugation have a porous structure and water can be drained either through the cracks that have been developed under the vacuum pressure or by the micro-...