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Enhanced dewatering remains a major challenge in sludge disposal. In this paper, a thermal solidification treatment under low temperatures was first and successfully employed to improve the dewaterability of sludge from water-based ink wastewater. A total of 95.1% of dewatering ratio, 36.6% of moisture content, and 91.9% of sludge volume reduction could be acquired at 75 °C and 30 min setting time by the reported approach. The DSC results indicated that a large amount of bound water trapped in sludge could be released into the bulk solution to become free water after thermal solidification treatment. The bound water content of sludge can be reduced from 3.40 to 0.20 g g−1 dry solid. The reported thermal solidification treatment is a thermophysical process that does not involve the solubilization of solid substrates and does not cause an increase in the COD value of dehydrated water. The obtained sludge after cooling was a clot of compacted cake with a uniform coralline-like structure. The softening and shrinking of acrylic resin within the sludge during heating contributed to the formation of compacted cake and thus enhanced the dewaterability. This study offers an economical and efficient treatment of sludge for the water-based ink printing industry. [ABSTRACT FROM AUTHOR]

Sludge treatment reed bed planted (STRB) with Phragmites australis (P.australis) and Arundo donax (A.donax) was assessed in the presence of Eisenia fetida under control condition during the dry season. Worm-planted units were fed with mixed sewage sludge (dry and volatile solids of 29.44 g DS.L−1 and 24.23 g VS.L−1). Sludge loading rates (SLR) of 50, 60, and 70 kg DS m−2 year−1 were examined to assess dewatering efficiency. Surface layers in units with P.australis and A.donax achieved DS of 80 and 81% at a loading rate of 50 kg DS m−2 year−1, while their subsurface DS were 41 and 25%, respectively. Units with A.donax experienced plant loss when subjected to SLR exceeding 60 kg DS m−2 year−1. More than 10 cm of residual sludge accumulated on the top of units after a 2-month final rest. Evapotranspiration was greater in the unit with P.australis (5.23 mm day−1) compared to the unit with A.donax (4.24 mm day−1) while both were fed with 70 kg DS m−2 year−1. Water loss contributions from residual sludge layer, drained water, and evapotranspiration were 3, 46, and 51%, respectively. Units with P.australis indicated 20% higher water loss compared to units with A.donax. Although the drained water quality improved over time, it did not meet standard limits. The residual sludge layer contained macro and micronutrients, and heavy metals with a significant elemental order of N > Ca > P > S > mg > K (N:P:K = 31:8:1), Fe > Na > B > Mn > Mo and Zn > Cr > Cu > Pb > Ni > Cd. Overall, STRB could be a sustainable alternative technology to conventional sewage sludge management techniques. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study presents the application of cationic celluloses in sludge dewatering. The source of cellulose used in this study were microcrystalline cellulose and alkaline-treated rice straw. The cationic celluloses were synthesized in a two-step reaction involving oxidation of cellulose with sodium periodate and followed by Schiff base reaction with Girard reagent T to introduce quaternary ammonium cations. The functional groups and chemical structure were confirmed by FTIR and NMR spectroscopy. The molecular weight and cationicity index of cationic cellulose were determined. Owing to their low molecular weight, the cationic celluloses functioned as coagulants and brought about charge neutralization through electric patches. The cationic celluloses were effective in promoting rapid sludge settling and improving the sludge filterability. The cationic celluloses are eco-friendly and non-toxic alternatives to acrylamide-based flocculants. [ABSTRACT FROM AUTHOR]

Sewage sludge was considered a critical reservoir for the propagation of antibiotic resistance genes (ARGs) and its treatment and disposal were important for the environment and human health. This study investigated the efficiency of the bioleaching technology for reducing eight typical antibiotic resistance genes in municipal sewage sludge, which was an emerging environmentally friendly technology for sludge dewatering. The prevalence of forty ARGs subtypes (including two mobile gene elements, MEGs) and one 16SrRNA gene were concerned with high throughput quantitative polymerase chain reaction during sludge bioleaching and a total of sixteen ARGs subtypes (including two transposase genes) were presented in the sludge samples. These genes were significantly decreasing after bioleaching, namely, one sulfonamide resistance gene (sul2), five tetracycline resistance genes (tetA-02, tetB-01, tetG-01, tetO-01, tetX), four macrolide-lincosamide-streptogramin B (MLSB) resistance genes (ermF, mphA-01, mphA-02, lnuB-01), two β-lactam resistance genes (blaOXA1/blaOXA30, blaPSE), two aminoglycoside resistance genes [aac(6´)-Ib, strB] and two MEGs (tnpA-01, tnpA-03). This result indicated that the bioleaching technology could significantly reduce the ARGs abundance of sewage sludge and the maximum removal efficiency was sixty-eight percent (mphA-02) and other ARGs subtypes such as tetA-02, tetB-01, mphA-01 and blaOXA1/blaOXA30 were decreased over fifty percent. The characteristics of Acidithiobacillus ferrooxidans contributed to the sludge bioleaching and may influence the diversity and composition of bacterial community and consequentially result in the change of ARGs abundance. [ABSTRACT FROM AUTHOR]

This research was carried out to evaluate the effects of different dosages (1.85–4.44 g kg−1 Ts−1) of three cationic polyelectrolytes with charge densities (CD) of 20%, 40%, and 60% on the dewatering properties of an aerobically digested sludge. The sludge was collected from the sludge processing line in a wastewater treatment plant in the city of Mashhad, Iran (MWWTP). To assess the sludge dewatering properties, parameters such as specific resistance to filtration, sludge cluster geometry, filtration rate, and filtrate turbidity and volume were measured. The experimental results were then compared with the effects of a reference polyelectrolyte that was used in the conditioning of the sludge in that treatment plant. The results indicated that the sludge samples treated with the polyelectrolyte of the highest CD matched better dewatering performance than the samples conditioned with the other two polyelectrolytes. This polyelectrolyte (60%CD) presented its best effects at the dosage of 4.07 g kg−1 Ts−1. With this dosage, its performance was similar to the performance of the reference polyelectrolyte at the dosage of 4.44 g kg−1 Ts−1. [ABSTRACT FROM AUTHOR]

The advanced anaerobic digestion process enhances sludge resource utilization. However, thermal hydrolysis pretreatment of anaerobically digested sludge reduces dewatering efficiency due to excessive organic matter decomposition. This necessitates significant time and effort for sludge conditioning in wastewater treatment plants. Using conditioning agents can achieve high dewatering efficiency. This study investigates how the order of adding coagulants and flocculants impacts the dewatering performance of digested sludge. The results indicate that, compared to the flocculation–coagulation process with the same dosage, the coagulation–flocculation process leads to a 15–20% increase in the average particle size of digested sludge. The content of polysaccharides and proteins in S-EPS decreases by 28.8–30.8% and 10.1–11.3%, respectively. The filter cake solids content increases by 8.5%, and there is an increase in surface water channels within the flocs. This is because initially adding coagulants efficiently adsorbs small particles, forming larger aggregates that settle effectively. This promotes the breakdown of extracellular polymeric substances, releasing more bound water. Adding flocculants later bridges the aggregates, further enhancing settling and filtration performance, thereby improving sludge dewatering efficiency. These research findings contribute to a better understanding of the mechanisms of coagulant and flocculant co-conditioning for digested sludge and provide recommendations for optimizing sludge conditioning steps. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Applied Chemical Industry is the property of Shaanxi Research Design Insitute of Petroleum & Chemical Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the effort to identify sustainable sludge management options, pilot-scale sludge treatment reed beds (STRBs) were tested and assessed in the Sultanate of Oman in the first integrated experimental study of this nature-based solution in the Middle East region. A total of 18 pilot STRB units were established and monitored for almost 2 years; half were planted with native Phragmites australis reed species, and half served as unplanted control units. Employing a randomized complete block design, the study examined varying sludge loading rates (SLR) of 75, 100, and 125 kg/m2/year. Results underscored the effectiveness of STRBs in reducing the sludge volume, with observed reductions reaching 98.0% of the applied sludge volume, particularly prominent in the SLR75 units. During the final resting phase, the STRBs showed slightly higher concentrations of total Kjeldahl nitrogen (TKN) and total phosphorus (TP) compared to the unplanted beds, while maintaining concentrations lower than those of the applied activated sludge. Furthermore, heavy metal concentrations were consistently diminished in the STRBs compared to the unplanted beds, aligning with the established national and international standards for sludge reuse in agricultural contexts. The results of this study provide the first valuable insight into the potential of STRBs as an effective, sustainable, and climatically suitable approach for sludge dewatering. Specifically, an SLR of 100 kg/m2/year is proposed as an optimum loading rate for the hot and arid Middle East climate. This study advances our understanding of STRBs as a pivotal component in the realm of arid-region sludge treatment, shedding light on their capacity to facilitate enhanced dewatering, mineralization, and nutrient removal, thereby contributing to the broader discourse on sustainable waste management practices. [ABSTRACT FROM AUTHOR]

Sludge biochar supported Fe(II) (Fe(II)-SBC) was successfully prepared using waste activated sludge as peroxydisulfate (PDS) activator to condition sludge for deep dewatering. The experimental results showed that Fe(II)-SBC with FeO on it could effectively active PDS to produce ${\rm SO}_4^{-\cdot }$ SO 4 − ⋅ and ${\rm HO}\cdot$ HO ⋅. The radicals could destroy the structure of sludge cells and extracellular polymeric substance (EPS), transformed the hydrophilic and tightly bound EPS into soluble-EPS, degrade partial proteins and polysaccharides and released bound water. The negatively charged groups on sludge floc were dripped off by ${\rm SO}_4^{-\cdot }$ SO 4 − ⋅ / $\; {\rm HO}\cdot$ HO ⋅ or neutralized with Fe2+, Fe3+, H+, or Fe(II)-SBC, leading to an increase in zeta potential to −2.24 mV and sludge destabilization. The residual Fe(II)-SBC served as a skeleton builder that decreased the compression coefficient of the sludge cake to 0.75. Under the combined functions, the CST and SRF were reduced by 70% and 82.7%, respectively, and Wc was reduced to 72.4%. The byproducts of Fe3+ and SO42- finally remained in sludge cake in the form of NaFeSi2O6 and CaSO4. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The sludge treatment reed bed is a sustainable sewage sludge management technology that offers promising sludge dewatering and stabilisation, due to its low energy and labour requirements, and minimal operating and maintenance costs. Despite numerous existing studies and increasing applications of sludge treatment reed bed in both developed and developing countries, the lack of standard system configurations and operating regimes led to several operational problems, including bed clogging and poor dewatering and mineralisation efficiency. Sludge dewatering and stabilisation in STBRs are complex processes governed by system- and operation-related factors such as the substrate media, macrophytes, loading regime, sludge characteristics, and climate conditions. Rather than the complex experimental study, process-based modelling has become a promising approach to investigating the influence of specific factors on the efficiency of sludge dewatering and stabilisation. This paper presents an overview of the critical system and operating parameters in sludge treatment reed beds and a summary of the interactions between the factors. Then, a framework of process-based modelling is proposed, which provides a useful platform to study the interactions of operating parameters and other factors in the complex processes of sludge dewatering and stabilisation, which supports the system design and optimisation of sludge treatment reed beds. [ABSTRACT FROM AUTHOR]

The process of wastewater treatment generates significant volumes of sludge, typically characterized by high water content. The practice of sludge dewatering plays a crucial role in reducing the volume of sludge and consequently, the associated costs of subsequent treatment, transportation, and disposal. This paper provides an exhaustive and impartial summary of research trends in sludge dewatering, spanning the period from 1993 to 2022. The bibliometric data utilized in this study were sourced from the Web of Science Core Collection database. Over 30 y, 5,836 papers have been published on sludge dewatering, witnessing a rapid growth trend in the number of published papers. The highest contributions in terms of the number of papers were made by authors hailing from China, followed by authors from the USA, Canada, Australia, and Japan. An analysis of keywords indicated that anaerobic digestion was the most frequently used. Three prominent research hotspots emerged: the impact of extracellular polymeric substances on sludge dewatering; the role of thermal hydrolysis in enhancing sludge anaerobic digestion; and the dual aspects of hydrothermal carbonization and heavy metals recovery in the context of sludge reuse and disposal. [ABSTRACT FROM AUTHOR]

This article presents the experience in the field of using ultrasonication as a pre-treatment method of SS (sewage sludge). On the basis of a review of the literature, the effect of pretreatment of sewage sludge by US (power ultrasound) with different parameters on SS quality parameters and energy effects of the process was presented. The status of commercial applications of US as a sewage sludge pretreatment method was also presented, using the example of wastewater treatment plants in Poland. It was shown that the effective management of SS is an important technological and environmental problem in many wastewater treatment plants. Therefore, new strategies for dealing with this by-product are constantly being sought. In large wastewater treatment plants, the dominant method of stabilizing SS is AD (anaerobic digestion). However, due to the characteristics of SS, it shows low efficiency. Among the numerous strategies, US is one of the new technologies that is finding several full-scale implementations. Its application allows for solubilization of organic matter, disruption of microbial cells, as well as SS floc description and enzyme release. A number of benefits can be obtained as a result of these developments, including increased methane production, improved reaction kinetics and removal of organic matter, as well as enhanced settability and dewatering of SS, thus contributing to savings in wastewater treatment plants. [ABSTRACT FROM AUTHOR]

During the dewatering process, centrate is produced, which is returned to the beginning of the technological system. The quality of the resulting centrate, and therefore the size of the returned load of pollutants, affects the demand for electricity in the process of biological wastewater treatment. The following study presents the results of centrate quality tests at five wastewater treatment plants located in Poland. The dependence between suspended solids content and ammonia and COD concentrations in the centrate was determined. It was estimated that an increase in the overall suspended solids leads to an increase in COD by about 1.15 kgCOD/kgTSS. No correlation was found between TSS concentration and ammonia. It was calculated that the complete elimination of suspended solids from the sludge would reduce the electricity consumption for all five objects by about 535 MWh/y. [ABSTRACT FROM AUTHOR]

To enhance sludge dewatering performance, Zero-valent iron/peroxymonosulfate/walnut shell powder was used to condition sludge at 55 °C and pH=3 (ZVI/PMS/WSP-T/pH), and the dewatering mechanism was also analyzed. The results showed that the capillary suction time (CST) and water content of sludge cake (Wc) were reduced to 6.8 s and 62.1%, respectively, and net sludge yield (YN) increased to 58.74kg/(m2·h) after being treated by ZVI/PMS/WSP-T/pH. The thermal and acid conditions could promote the corrosion of Fe2+ from ZVI and enhance PMS to produce more SO4−· and ·OH. The radicals combined with acid and thermal hydrolysis could efficiently reduce extracellular polymeric substances (EPS), especially tightly bound EPS (TB-EPS), destroy sludge floc and release bound water. The stripping off of EPS and neutralization of Fe3+, Fe2+ and H+ caused the zeta potential to increase to −0.91 mV The flocculation of cations and adsorption of WSP further increased the fractal dimension to 1.71. Moreover, the rigid and porosity structure of WSP increased sludge incompressibility and formed channels for water. Under the combined oxidation, acid/thermal hydrolysis, re-aggregation and skeleton builder functions, the sludge dewatering performance was greatly improved. [ABSTRACT FROM AUTHOR]

The article discusses the issue of dewatering sludge from municipal wastewater. Separating solids from sewage sludge constitutes one of the initial steps in managing sewage sludge for further use or processing. The process of removing water from sewage sludge is particularly significant due to its high content in the raw sludge. This translates into problems with transporting and storing sludge. Additionally, the high water content relates to a reduction in the calorific value of the sludge. This paper focuses on the effect of adding polyelectrolytes and solid mineral substances on increasing the efficiency of the sludge dewatering process and eliminating total carbon from the oversedimentary water. The technical aspects of preparing sludge prior to dewatering are described on the basis of studies conducted on municipal sewage sludge. This research focused on conditioning and separating solids from wastewater coming from a selected treatment plant in terms of achieving the lowest final hydration and lowering the amount of total organic carbon in the leachate. The change in sludge compressibility after conditioning, the efficiency and speed of the filtration process were also analysed to reveal the mechanisms involved in the dewatering process. [ABSTRACT FROM AUTHOR]

The sludge dewatering is a significant part of municipal wastewater treatment industry, and efficient disposal techniques for the sludge dewatering is still a challenge among worldwide environmental fields. To achieve sludge reduction, the research and exploitation of environment-friendly natural polymer dehydrating agents have caused broad attention. In this study, a coconut shellbased composite was prepared by grafting hydroxypropyltrimethyl ammonium chloride chitosan (HACC) on the surface of coconut shell skeleton particles as a novel type of dewatering agent. The response surface methodology was used to optimize the preparation process of grafted coconut shell-based skeleton particles. The consumption per unit area of HACC could reach 0.1732 g/g under the optimal preparation conditions: reaction temperature at 40°C, material particle size at 120-200 mesh, mass ratio of M1:M2 at 0.75 without dilution, and ultrasonic time for 5 min. Compared to the composites without graft, the dewatering rate of sludge was obviously improved by the grafted coconut shell-based composites under the same treatment procedures. Moreover, the grafted coconut shell-based composite also possessed the potential for effectively adsorbing the total organic matters in sludge dewatering filtrate. This work provides a promising dehydrating agent and disposal method for the practical application of municipal sludge dewatering. [ABSTRACT FROM AUTHOR]

Sludge is a by-product of wastewater treatment, and it has a high-water content. Sludge dewatering is typically performed to reduce its water content prior to its disposal. Dewatering is implemented by combining certain reagents with the sludge followed by a low- or high-pressure process to extract the water from the sludge thereby forming dry solids (DS). The overall objective is to simultaneously minimize the water content of the sludge and the total operating cost. However, these objectives may be conflicting in nature. To address this, a fuzzy optimization model which integrates these two objectives is developed to determine the satisficing solution and to identify the optimal condition in terms of cetyl trimethyl ammonium bromide (CTAB), ferrous ion (Fe2+), and hydrogen peroxide (H2O2) dosage. The optimization model includes—(1) an empirical equation which describes the influence of chemical reagent dosage on the water content of the sludge; (2) operational costs associated with chemical reagent dosage; and (3) cumulative uncertainty on water content. The ε -constraint is used to determine the Pareto frontier. The integration of the three variables is observed to enhance the dewaterability of the sludge. The optimal solution results in Fe2+, H2O2, and CTAB dosages of 1.00 mg g−1 DS, 204.53 mg g−1 DS, and 162.96 mg g−1 DS, respectively. This results in an optimal water content of 67.97%, an operating cost of 1,783.18 USD L−1, and an overall satisfaction level of 40.47%. [ABSTRACT FROM AUTHOR]

The dewatering process reduces the water quantity in sludge, allowing the decrease in its volume, which facilitates its storage, transport, stabilization, and improves the post-treatment efficiency. Chemical polymers including aluminum sulphate and polyaluminum chloride were applied as flocculants in the conditioning process in order to prepare sludge for dewatering. However, these synthetic polymers may cause risks for human health, and should be substituted with ecofriendly and safe materials. These materials include plant-based flocculants, animal-based flocculants, and microbial-based flocculants. Sludge dewaterability was evaluated by considering many parameters, such as moisture content (MC), dry solids (DS), specific resistance to filtration (SRF), capillary suction time (CST), and sludge volume index (SVI). The use of microorganisms for sludge dewatering is an available option, since many strains (R. erythropolis, A. ferrooxidans, P. mirabilis, T. flavus, etc.) demonstrated their ability to produce polymers useful for dewatering sludge from various origins (chemically treated primary sludge, activated sludge, anaerobically digested sludge, etc.). For plant-based flocculants, only okra (Abelmoschus esculentus), cactus (Opuntia ficus Indica), moringa (M. oleifera), and aloe (A. vera) plants are examined for sludge dewatering. Compared to synthetic polymers, plant-based flocculants showed a viable alternative to chemicals and a step forward in green sludge treatment technology. Among the animal-based flocculants, chitosan and aminated chitosan were able to reduce the SRF (SRF reduction rate > 80%) of the anaerobically digested sludge. A new strategy using methylated hemoglobin also showed a significant enhancement in cake solid content of sludge (47%) and a decrease in sludge bound water content of 17.30%. Generally, extensive investigations are needed to explore and optimize all the related parameters (operating conditions, preparation procedure, production cost, etc.) and to choose the appropriate materials for large-scale application. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to that the continuous growth of global sludge production has caused serious environmental problems, the reduction and harmless treatment of sludge is imperative. Taking an actual sludge dewatering project based on biochemical conditioning and vertical filter press in a sewage treatment plant of Guangdong's Dongguan as an example, this study minimized sludge water content and control economic cost without adding lime by regulating the optimal proportion of lactic acid bacteria (LAB), polyacrylamide (PAM), and polymeric aluminum ferric chloride (PAFC). The results demonstrate that the system runs stably for 190 days, the average water content decreases to 61.59%, and the direct running cost of sludge dewatering is 94.13 yuan/ton under optimal conditioning scheme of 2.5‰ PAM + 1.5‰ LAB + 2.0‰ PAFC. Our study effectively reduces the sludge water content while controlling cost, which can also provide practical engineering reference and theoretical basis for the combined application of biochemical conditioning and vertical filter press for sludge dewatering. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Flocculation is an important pretreatment technology for sludge dewatering, and the flocculant's performance is the key factor to determine the flocculation effect. Cationic polyacrylamide (CPAM) is commonly used in dewatering and conditioning of printing and dyeing sludge (PD sludge), and the research of high-efficiency flocculant is a hot spot in the field of PD sludge dewatering. Hydrophobic butylacrylate (BA) and (2-(Methacryloyloxy)ethyl) trimethylammonium chloride (DMC) were introduced into the copolymer, and amphiphilic (hydrophilic/lipophilic) CPAM, namely TP-ADB, with microblock structure was synthesized by ultrasonic initiated template copolymerization in this study. The functional group composition of TP-ADB was determined by FTIR and 1H NMR. Thermogravimetric analysis (TGA) showed that TP-ADB had good thermal stability. The amphiphilic rheological properties of the copolymer were measured according to the apparent viscosity. In addition, 1H NMR and TGA results confirmed the existence of microblock structure in the copolymer chain. The polymerization mechanism was discussed by association coefficient (KM) measurement. The results showed that the template copolymerization initiated by ultrasonic followed the law of free radical copolymerization. The pre-adsorption of DMC with sodium polyacrylate template (NaPAA) before the reaction confirmed that the template polymerization accorded with ZIP I mechanism. The cationic microblock structure and hydrophobic association of TP-ADB promoted the dewatering performance of PD sludge (FCMC = 72.9%, turbidity removal rate = 98.9%, SRF = 4.2 × 1012 m·kg−1). Hydrophobic association enhanced the bridging, sweeping, and net catching effect, and promoted the growth of floc size and fractal dimension. Cationic microblock structure can produce compact floc with higher mechanical strength by enhancing electrical neutralization and electrical patching. As a skeleton, the compressibility of filter cake was reduced and the permeability was enhanced, and the PD sludge dewatering effect was significantly improved. [ABSTRACT FROM AUTHOR]

Municipal sludge is characterized by high organic matter content, high viscosity, and fine particles, resulting in poor dewatering performance. This article analyzes the composition and properties of municipal sludge, examines the factors affecting the dewatering performance of sludge and the mechanisms corresponding to each influencing factor, and introduces chemical conditioning in detail. Chemical conditioning includes flocculation conditioning, oxidation conditioning, acid-base conditioning, and aggregate conditioning. The principles and applications of existing sludge conditioning technologies are systematically analyzed. By comparing the advantages and disadvantages of different technologies, it is pointed out that the key to developing sludge conditioning technology lies in developing a more appropriate combination of the sludge conditioning and dewatering process according to the sludge quality of different municipal wastewater treatment plants, taking into account their local environment, input costs, subsequent sludge disposal methods, and other factors, and further optimizing the sludge dewatering process by developing new efficient and environmentally friendly sludge conditioning agents. [ABSTRACT FROM AUTHOR]

The dewaterability of waste activated sludge (WAS) plays the key role in sludge dewatering in wastewater treatment plants. The magnetic field as a source of clean energy has been reported to be able to cause changes in sludge properties and to enhance sludge dewatering by chemical treatment. This paper focuses on the effect of pre-magnetization on the sludge dewatering performance by ozonation. The results showed that ozonation reduced the capillary suction time (CST) and water content of sludge cake (Wsc) of WAS. The CST reduced from 21.5 s to 12.7 s; and the Wsc reduced from 85.6% to 85%. However, the addition of pre-magnetization with a magnetic field did not make much improvement of the dewaterability. Further investigation on sludge properties such as EPS, TOC, particle size, and the SEM images of the treated WAS showed that the pre-magnetization prior to ozonation led to stronger oxidation and WAS particle broken, which was proofed not necessarily correlated to sludge dewaterability enhancement. [ABSTRACT FROM AUTHOR]

Copyright of Applied Chemical Industry is the property of Shaanxi Research Design Insitute of Petroleum & Chemical Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, we proposed an advanced oxidation process of pyrite (FeS2) and peroxymonosulfate (PMS) and prepared a modified polyaluminum chloride biochar (P-BC). The motivation is to use the combination of FeS2 + PMS + P-BC to improve waste activated sludge (WAS) dewaterability. The method to improve the sludge dewatering effect with the combination of FeS2 + PMS + P-BC is as follows: in the first step, pour 0.75 g/g TSS FeS2 and 0.6 g/g TSS PMS into the sludge, and stir for 15 min. Then, add P-BC and stir for 5 min; complete the entire WAS processing process. The vacuum filtration test was used to evaluate the dehydration effect. The water content (Wc) and specific resistance to filtration (SRF) of the raw sludge can be reduced from the original values of 92% and 2.36 × 1013 m/kg to 67% and 9.89 × 1011 m/kg, respectively. The results showed that the combination of FeS2 + PMS + P-BC can effectively improve the sludge dewatering effect through oxidation. A laser particle size analyzer is used to observe changes in sludge particle size. The median diameter of sludge particles increased from 55.37 to 64.56 μm. A zeta analyzer to is used observe changes in sludge zeta potential. The zeta potential of sludge particles increased from − 15.8 to 0.4 mV. In the analysis of extracellular polymeric substances (EPS) of sludge, it was found that protein (PN) and polysaccharide (PS) in EPS decreased significantly. To further analyze the phenomenon of PN and PS drop, excitation-emission-matrix spectra (3D-EEM) was used. To observe the changes of sludge functional group, X-ray photoelectron spectroscopy was used. It was found that FeS2 + PMS + P-BC can destroy the functional groups of sludge, such as O–H, C–C, and O═C—NH– related to proteins and polysaccharides. [ABSTRACT FROM AUTHOR]

In this study, cationic polyacrylamide (CPAM)-modified diatomite and cetyl trimethyl ammonium bromide (CTAB)-modified diatomite were synthesized and used as conditioners for sewage sludge dewatering. The effects of these two types of modified diatomite on the dewaterability and settling performance of the activated sludge were studied. The mechanisms of the two modified diatomite types in the activated sludge system were elucidated. The efficiency of the CPAM-modified diatomite was better than that of the CTAB-modified diatomite in improving the settleability and dewaterability of sludge. The results indicated that specific resistance to filtration (SRF) was decreased from 8.52 × 1012 to 0.92 × 1012 m/Kg, and the water content in the remaining sludge cake after pumping filtration was decreased from 92.2 to 68.1% by adding 0.4% of CPAM-modified diatomite and pH = 3.5, which resulted in excellent sludge settling of activated sludge. Further studies showed that the polymer/surfactant adsorbed in diatomite increased sludge dewaterability and improved the sedimentation rate owing to stripping extracellular polymeric substances (EPS) and damaging the internal structure of the sludge, leading to sludge conduce bound water release. According to scanning electron microscope (SEM) images, the two types of modified diatomite powder maintained the porous structure and showed a more complete and uniform structure compared to natural diatomite. [ABSTRACT FROM AUTHOR]

Flocculation is one of the commonly used sludge conditioning methods in water supply plants, which can improve the sludge dewatering performance by reducing the specific resistance of sludge (SRF), decreasing the amount of sludge, and finally lowering the transportation cost and subsequent disposal cost of sludge. Therefore, it is particularly important to develop new and efficient flocculants. In this paper, the template copolymer of acryloxy trimethylammonium chloride (DAC) and acrylamide (AM) was successfully synthesized by microwave-template copolymerization (MV-TP) using sodium polyacrylate (NaPAA) as template. The template copolymer was analyzed by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), and scanning electron microscopy (SEM). It was found that this template copolymer had obvious cationic microblock structure. In addition, the test results of association constant (KM) and polymerization kinetics showed that the MW-TP was assigned to free radical initiated polymerization and the polymerization mechanism was I Zip-up (ZIP). It confirmed the formation of cation fragment structure again. Due to its dense positive charges in this new cationic microblock structure, it greatly improved the functions of electric neutralization, electrical patching, and adsorption bridging. The cationic fragment structure in the template copolymer could help to generate large and dense floc structure and form stable drainage channels. Under external pressure, these large and compact floc structures had greater compressive resistance, which avoided deformation and blockage of drainage channels and voids. It was beneficial to reduce SRF and evidently enhanced sludge dewatering performance. [ABSTRACT FROM AUTHOR]

The article presents the plant trial results to evaluate the use of organic polymer AS-43124M as filter aid for conditioning and dewatering of sludge from gas scrubbing system in ferroalloy plant. It is shown that using the filter aid allows increasing sludge throughput of plate-and-frame presses due to increasing sludge filtration rate, to reduce cake moisture and suspended solids in filtrate, minimize sludge sticking to the filter cloth thereby facilitating and speeding up release of the cake from the medium during the discharge stage. At present moment organic polymer AS-43124M is used as filter aid for dewatering of sludge from gas scrubbing system in ferroalloy plant on plate-and-frame presses. [ABSTRACT FROM AUTHOR]

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 ( SO 4 − ∙) 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. [ABSTRACT FROM AUTHOR]

Flocculant played an important role in water treatment and sludge dewatering. It is imperative to design and synthesize an eco-friendly and biodegradable flocculant based on natural polymer. In the present work, a new amphoteric CMC-based flocculant, CMC-g-PDMC was synthesized via grafting DMC onto hydroxyl of CMC initiated by potassium persulfate under traditional heating condition. The optimal graft copolymerization condition was optimized by orthogonal experiment. The structure, morphology and thermostability of the obtained graft copolymer were characterized by measuring FT-IR, XRD, SEM and TGA analyzer, respectively. Moreover, comparing with the commercial flocculant PAM, PAC and CPAM, the dewatering capacity of municipal sludge was evaluated using CMC-g-PDMC by FCMC, SRF, SVI and light transmittance. It suggested that the flocculation to municipal sludge was related to the ion properties of the flocculant. [ABSTRACT FROM AUTHOR]

FeSO4 was used to activate K2S2O8 mixed with paper sludge to condition activated sludge, and its effect on sludge dewaterability was investigated. Interaction effects of various parameters on sludge dewaterability were investigated and analysed by considering the moisture content of cake, specific resistance to filtration (SRF) and capillary suction time (CST) as indicators and the Box–Behnken design of response surface methodology (RSM). Results indicated that the moisture content of cake, SRF and CST decreased from 74.52 to 69.57%, 25.39 × 1012 to 11.80 × 1012 m/kg and 199.8 to 146.4 s, respectively, under optimal conditions. RSM results presented that only 0.13% of the response values cannot be interpreted with this model, and the three‐factor interaction was observed to be significant. Additionally, sludge dewaterability mechanism observed that K2S2O8 mixed with paper sludge used the strong oxidising properties of SO4−• to crack sludge flocs. Fine fibres and calcium carbonate in the paper sludge played important roles as the skeleton support in the sludge filtration process, and the internal moisture was rapidly eliminated. [ABSTRACT FROM AUTHOR]

Featured Application: This review paper is the first one that summarizes the limited available information on the application of the green technology of Sludge Treatment Reed Beds (STRBs) for dewatering of industrial sludge. Although STRBs are widely used as a low-cost and sustainable nature-based solution for domestic sludge dewatering, the number of applications for industrial sludge treatment is very limited. This study presents the few available pilot and full-scale STRB systems from various countries that receive and treat sludge from industrial wastewater treatment plants or sludge from Water Works. The overall efficiency and performance for this particular application is also discussed along with the advantages of this green technology. Finally, this study proposes the optimum design parameters for proper dimensioning and operation of STRBs for industrial sludge dewatering. Sludge treatment reed beds (STRBs) are an established sludge treatment technology with multiple environmental and economic advantages in dewatering sludge generated during domestic wastewater treatment. However, little is reported regarding their appropriateness and efficiency for the treatment of sludge produced during industrial wastewater treatment and from water works. These sludge types may have significantly different quality characteristics than typical domestic sludge and may contain constituents that could affect their dewaterability. Therefore, the dewatering of these industrial sludge types is usually tested in small-scale pilot STRBs before the construction of full-scale systems. This paper presents and summarizes the state-of-the-art experience from existing pilot and full-scale STRB systems from various countries and climates treating sludge from various industrial sources, evaluates the suitability and the advantages of this sustainable treatment technology, and proposes the required dimensioning for efficient full-scale STRB operation and performance. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The addition of the surfactant can greatly reduce the moisture content of the sludge. But little research has been done on the synthesis of surfactants and the mechanism of dehydration. Thus, a novel cationic surfactant ZWY-28 with higher surface activity and more surface charge was investigating for sludge dewatering in this research. Results showed that when the content of ZWY-28 was 1% (0.14 g/L), the specific resistance to the filtration of sludge had a minimum value of 2.04 × 1012 m/kg, the moisture content of the dehydrated sludge cake reached a minimum of 78.9%, the bound water reduced to 6.32 g/g, decreased by 39.2%. What's more, the ZWY-28 is extremely helpful in releasing Extracellular polymers substances from sludge, lead to the removal of bound water, which is the key point of affecting sludge dewatering. The study clearly illustrated that the surfactant ZWY-28 accelerated the dewatering process and could be used as a potential agent for sludge. Meanwhile, it provides ideas for the selection and structure design of surfactants in sludge dewatering. [ABSTRACT FROM AUTHOR]

Copyright of Waste Forum is the property of Czech Environment Management Center (CEMC) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: The aim of this study was to harvest a biopolymer from acid hydrolyzed rice stover with phosphate salts as pH buffer, and to enhance sludge dewatering by using this biopolymer combined with chemicals. Methods: Rhodococcus erythropolis was first inoculated in 250 mL seed medium and incubated on a reciprocal shaker at 150 r min−1 and 35 °C for 24 h, and then, 2.0% (V/V) of the above inoculum was used to inoculate the cultivation medium and incubated in the same procedure to produce biopolymer. For sludge dewatering, the biopolymer was added into a 200 mL mixing chamber with 100 mL of sludge, and then the mixtures were stirred at the design agitation speed for 10 min, finally, dry solids (DS) and specific resistance to filtration (SRF) of the sludge were examined. Results: Rhodococcus erythropolis obtained its maximum biomass (OD600) of 0.79 when 5 g L−1 K2HPO4 and 2 g L−1 KH2PO4 were presented in cultivation medium. The fermented broth from the medium with phosphate salts appeared high flocculating activity of 94.6%, higher than that from the phosphate-free medium. Meanwhile, the biopolymer performed a great potential in sludge dewatering, after treated by this biopolymer, DS and SRF of the sludge reached 18.4% and 4.8 × 1012 m kg−1, respectively. Sludge dewatering was further enhanced when the biopolymer and polyaluminum chloride (PAC) were used simultaneously, under the optimal sludge treatment conditions of biopolymer of 13.5 g kg−1, PAC of 19.4 g kg−1, and pH of 8.1, sludge SRF decreased by 73.5% and DS increased to 24.1%, respectively. Conclusion: It is meaningful to enhance the dewatering of the sludge by the composite use of the biopolymer and PAC. [ABSTRACT FROM AUTHOR]

The use of engineering textile materials has emerged as a viable alternative to conventional methods of sludge dewatering in numerous application areas including municipal wastewater, mining, and pulp and paper. Previous studies have focused on the development of empirical ratios between dewatering performance and the porous properties of the textile material, the challenge is that the latter is difficult to characterize using currently available techniques. In this study, a series of dewatering filters were produced using advanced microfabrication techniques to create well-defined slit-pore geometries; a full-factorial design-of-experiments was employed to evaluate the effects of slit-pore dimensions and slit-pore spacing on the cake layer development and overall dewatering performance in constant-rate dewatering tests with municipal digestate that had been pre-treated with a commercial polymer flocculant. The results from this study provide new insights into the importance of the cake layer in textile dewatering and the impact of textile porosity and flocculation conditions on dewatering performance. It was found that an inverse relationship exists between the porosity of a dewatering fabric and both medium and cake resistances between 0.1% and 1.0% filter porosity, while these properties are comparatively independent of pore structure beyond 1.0%. In addition, the efficacy of the polymer pre-treatment conditions employed was determined to have a substantial impact on solids retention. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shaanxi University of Science & Technology is the property of Journal of Shaanxi University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coagulation/flocculation is a major phenomenon occurring during industrial and municipal water treatment to remove suspended particles. Common coagulants are metal salts, whereas flocculants are synthetic organic polymers. Those materials are appreciated for their high performance, low cost, ease of use, availability and efficiency. Nonetheless, their use has induced environmental health issues such as water pollution by metals and production of large amounts of sludges. As a consequence, alternative coagulants and flocculants, named biocoagulants and bioflocculants due to their biological origin and biodegradability, have been recently developed for water and wastewater treatment. In particular, chitosan and chitosan-based products have found applications as bioflocculants for the removal of particulate and dissolved pollutants by direct bioflocculation. Direct flocculation is done with water-soluble, ionic organic polymers without classical metal-based coagulants, thus limiting water pollution. Chitosan is a partially deacetylated polysaccharide obtained from chitin, a biopolymer extracted from shellfish sources. This polysaccharide exhibits a variety of physicochemical and functional properties resulting in numerous practical applications. Key findings show that chitosan removed more than 90% of solids and more than 95% of residual oil from palm oil mill effluents. Chitosan reduced efficiently the turbidity of agricultural wastewater and of seawater, below 0.4 NTU for the latter. 99% turbidity removal and 97% phosphate removal were observed over a wide pH range using 3-chloro-2-hydroxypropyl trimethylammonium chloride grafted onto carboxymethyl chitosan. Chitosan also removed 99% Microcystis aeruginosa cells and more than 50% of microcystins. Here, we review advantages and drawbacks of chitosan as bioflocculant. Then, we present examples in water and wastewater treatment, sludge dewatering and post-treatment of sanitary landfill leachate. [ABSTRACT FROM AUTHOR]

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 trimethylammonium chloride (CHPTAC) under alkaline condition. The performance of QLs was studied for various β values (molar ratios of CHPTAC to phenylpropanoid unit of lignin), flocculant dosages, pH values, kaolin concentrations, slow mixing rates and sedimentation times. The QL10 achieved the highest turbidity removal efficiency (εt) with increasing flocculant dosage, pH and kaolin concentration to the optimal conditions of 5 mg L−1, pH 7 and 1000 mg L−1, and required 20 min of sedimentation time at all the mixing rates tested. The flocculation kinetics agreed well with the particle collision model. The QL10 has good sludge dewatering properties compared to the alum. It also showed encouraging results in water quality analysis for sewage wastewater flocculation in comparison to that of the alum. This indicates the potential application of QL in treating water and wastewater. [ABSTRACT FROM AUTHOR]

Wastewater treatment generates considerable amounts of sludge. Reducing sludge volume by dewatering is an important part of many wastewater treatment processes. We investigated the effects of a combination of sodium dodecyl sulfate (SDS) and polydimethyldiallylammonium chloride (PDMDAAC) on anaerobically digested sludge dewaterability. Capillary suction time (CST) and specific resistance to filtration (SRF) were measured as indicators of sludge dewaterability. Extracellular polymeric substances (EPS) content, particle size, zeta potential, and bound water in sludge floc were also measured. We found that CST increased from 348.5 to 530.5 s as the SDS dosage increased. However, with a dose 0.03 g g-1 DS PDMDAAC only, SRF and CST were 3.78 × 1012 m kg-1 and 79.2 s; with a combined dose of 0.025 g g-1 DS SDS and 0.03 g g-1 DS PDMDAAC, SRF and CST decreased to 3.21 × 1012 m kg-1 and 68.7 s. These results indicate that above a certain dose, SDS reduces sludge dewaterability and that an optimum dose of SDS in sludge pre-treatment would improve subsequent PDMDAAC conditioning. Sludge conditioned with a combination of SDS and PDMDAAC increases dewaterability more than conditioned with SDS only or PDMDAAC only. Freeing EPS-bound water with SDS followed by re-flocculation using PDMDAAC gave improvement in sludge dewaterability. [ABSTRACT FROM AUTHOR]

Sludge dewatering is an important process for determining the operation cost of sludge disposal. Hence, improving the dewaterability of anaerobically digested sludge containing high water content is of paramount significance. For this challenge, we developed a novel process in which fibrous materials initially collected from a primary sedimentation tank, namely recovered fibers, were used as an auxiliary agent to improve the dewaterability of anaerobically digested sludge. The objective of this study was to investigate the feasibility of using the developed process to improve sludge dewaterability. Three fibrous materials individually recovered from the respective primary sedimentation tanks in different wastewater treatment plants (WWTPs) were used to investigate sludge dewaterability, organic C compositions, and calorific values. The recovered fibers showed comparable compositions irrespective of the WWTP. Six different WWTP sludge samples after anaerobic digestion were continuously supplied to three different dewatering devices, i.e., screw press, centrifuge, and belt press machines, with or without the supply of recovered fibers. Irrespective of the type of a dewatering device, the supply of recovered fibers mixed with the tested sludge samples at a feed ratio of 0.18–0.20 g-fibers/g-sludge (dry weight) reduced the amount of polymer flocculant by 13–50%, thereby displaying the superiority of the addition of recovered fibers. Furthermore, at fiber feed ratios of 0.20 g-fibers/g-sludge and 0.40 g-fibers/g-sludge when the rates of sludge supply and polymer flocculant were kept constant, the corresponding water contents in the dewatered sludge cakes decreased to about 74–76% and 69–72%, respectively. The consistent results regardless of the dewatering device or sludge sample showed the significance of the addition of recovered fibers for improvement in sludge dewaterability. [ABSTRACT FROM AUTHOR]

The difficulty of residual sludge dehydration is the major problem in sewage treatment. The reduction of moisture content in sludge can reduce the sludge volume significantly and is conducive to the subsequent disposal of sludge. As an organic polymer flocculant, chitosan (CTS) is widely used in water and waste water treatment. In this study, CTS was used in sludge treatment to improve the sedimentation and dehydration properties of sludge. When treated with CTS, the moisture content of sludge cake decreased from 85.9% to 83.0%, the SV30 decreased to about 1/2, and the sludge volume reduced to 82.9%. Further analysis showed that the zeta potential (ζ-potential) of the sludge changed from negative value to positive value, and the D50 of the sludge was larger than that of the raw sludge. In addition, when the moisture content of the sludge cake was reduced to the lowest, the concentration of extracellular polymeric substances (EPS) and SCOD was the largest and the /ζ/ decreased to the lowest. CTS improved the dehydration and sedimentation performance of sludge mainly by factors of electrical neutralization, adsorption bridging and dissolution of EPS. [ABSTRACT FROM AUTHOR]