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Sludge disposal is becoming an issue at the municipal solid waste incinerator (MSWI), especially for environmental and economic reasons. This paper describes a case study of the optimization of the sludge management (SM) system at the MSWI in the Czech Republic. The original concept of SM at MSWI was designed as waste-free. However, the present operation indicates that there is a need to carry out regular extraction and disposal of sludge settling at the bottom ash tank and the bottom of the retention basin. The current status of SM causes problems not only in terms of operation but it also entails significant financial costs given the necessary regular cleaning of tanks. The aim of the applied research presented in this paper is SM optimization by a mobile sludge dewatering (DW) press unit with optimal polymer combination for DW.

[Display omitted] • Both Cu+ and Cu+/H 2 O 2 facilitate sludge dewatering. • The CST reduction rate was about 80%. • Cu+ based treatments destructed the EPS matrix and increase the zeta potential. • Cu3+ was the predominant reactive species rather than hydroxyl radicals. The high water content of sewage sludge increases the processing costs and hampers its further disposal. Fenton technology has proven to be efficient and been widely used to enhance sludge dewaterability, but it usually needs acidification and subsequent neutralization, thus consuming a lot of chemicals. It's well documented that hydroxyl radicals produced in various Fenton or Fenton-like reactions play a crucial role in sludge dewatering. Based on the latest study, Cu+ and Cu+/H 2 O 2 pretreatments for the enhanced dewaterability of sludge without extra pH adjustment were proposed. Results showed that Cu+ with and without H 2 O 2 can significantly improve the dewatering performance of sludge, which was ascertained by a capillary suction time (CST) reduction rate of about 80 %. The proteins and polysaccharides in tightly-bound extracellular polymeric substance (TB-EPS) were decreased, while increased in soluble extracellular polymeric substance (S-EPS). In addition, a hydrophobic and porous surface was formed, and zeta potential increased after conditioned. These changes may release bound water and thus improve sludge dewaterability. The results of electron spin resonance and scavenging tests signaled that the Cu3+ was mainly accountable for the dissolution of EPS, rather than the hydroxyl radicals (OH). Our results substantiate and untangle a distinct reinforcement mechanisms for sludge dewatering by high valent copper (Cu3+). This study demonstrates for the first time that Cu3+ plays an important role in sludge dewatering, which has long been credited to hydroxyl radicals. It also urges re-evaluation of the Fenton(-like) system for sludge dewatering, given that Cu3+ could also cause potential oxidative destruction of EPS compared with reactive oxygen species. [ABSTRACT FROM AUTHOR]

Among the common treatment/disposal routes of excessive activated sludge from municipal wastewater treatment plant, dewatering process functions as an essential pre-/post-treatment for volume minimization and transportation facilitation. Since inorganic coagulants have long been criticized for their high dosage and solid residue in sludge cake, there is an urgent need for investigations regarding the potential of applying organic chemicals as the conditioner. In this study, combined use of poly dimethyldiallylammonium chloride (PDMD) and tannic acid (TA) were investigated as an all-organic co-conditioning method for sewage sludge pre-treatment. Results showed that this all-organic conditioning strategy can effectively improve the dewaterability of sewage sludge. The capillary suction time reduced from 128.8 s to 23.1 s, and the filtration resistance reduced from 1.24 × 1012 cm/g to 7.38 × 1010 cm/g. The moisture content of dewatered sludge cake decreased to as low as 55.83%, showing the highest dewatering efficiency reported so far. In addition, the combination of PDMD and TA maximized the treating efficiency with very limited consumption of conditioners (added up to 4% of total solid). Based on the physic-chemical and rheological property investigation, it was proposed that the intermediate molecular weight polymer-based flocculation process and the TA agent-based protein precipitation process, could remarkably strengthen the compactness and structure robustness of sludge. In all, this PDMD-TA-based conditioning method suggested practical significance in consideration of its cost-effectiveness and disposal convenience of sludge cake. [Display omitted] • An all-organic co-conditioning method was developed to dewater sludge in depth. • Moisture content of dewatered sludge cake decreased significantly to 55.83%. • The utmost conditioning effect was obtained with minimum organic conditioners. • Floc property was profoundly analyzed to explain the dewaterability enhancement. • Three-stage variation model was proposed to explain the conditioning process. [ABSTRACT FROM AUTHOR]

This paper studied the dewatering performance of modified kaolin conditioned sludge, and focused on the molecular composition and transformation of extracellular biological organic matter (EBOM) and supernatant dissolved organic matter (DOM) during the conditioning process. The results showed that the sludge dewatering performance was significantly improved after conditioning with modified kaolin. Under the dosage of 20% DS (200 g conditioner was added to each 1 kg sludge dry solids), the specific resistance to filtration (SRF) of sludge was reduced by 85.05%, the water content of sludge cake was decreased to 66.70%, and the time to filter (TTF) reduction rate was increased to 71.35%. The modified kaolin can broke the structure of sludge floc, which caused the transfer of organic matter from the solid phase to the liquid phase, thus promoting the release of bound water. In this process, the hydrophilic fraction in the inner layer of the sludge floc was released and enhanced the aromaticity of supernatant DOM. The transfer of proteins of the acidic fractions and polysaccharides of each fraction in the sludge EBOM to the supernatant DOM occurred. The reduction of hydrophobic and transitional proteins, hydrophobic and neutral humic acid-like substances, soluble microbial byproducts-like and fulvic acid-like materials in the sludge EBOM facilitated the breakage of the sludge floc. [Display omitted] • Sludge dewatering performance effectively improved by adding modified kaolin. • The release of protein and polysaccharide reduces the hydrophilicity of sludge. • Organic matters in the sludge EBOM transferred to the supernatant DOM. • Sludge floc structure was destroyed by modified kaolin. [ABSTRACT FROM AUTHOR]

Sludge dewatering is crucial for cutting the cost of sludge post-disposal in wastewater treatment plants. Response surface methodology (RSM) was used in this study to sufficiently investigate the interaction among persulfate, zero-valent iron (ZVI) and reaction time on the sludge dewatering. Under the experimental condition at the central point in RSM, the sludge moisture content was reduced to 54%. The sludge-based biochar obtained from the pyrolysis of persulfate-ZVI treated sludge at the central point in RSM was marked as SC-M and tested for catalytic activity. With the catalyst SC-M, the removal rates of m-cresol and total organic carbon (TOC) were 98.1% and 84.2%, respectively. The persulfate-ZVI treatment for sludge dewatering facilitated increasing the proportion of iron species in SC-M, which contributed to its high catalytic activity. M-cresol degradation with SC-M was a two-period reaction including an induction period and a rapid reaction with the apparent activation energy at a low level. This study integrates the sludge dewatering by persulfate-ZVI treatment and m-cresol degradation by catalytic oxidation with the biochar SC-M prepared from the dewatered iron-rich sludge, providing an effective, economic and environment-friendly approach for sewage sludge utilization and management. [Display omitted] • Sludge moisture content was reduced to 54% at the central point of experiments by RSM. • M-cresol removal rate with biochar from the persulfate-ZVI treated sludge reached 98.1%. • The magnetic property and catalytic activity were related with the iron species in catalyst. • The apparent activation energy was below 25 kJ/mol in the two-period degradation of m-cresol. [ABSTRACT FROM AUTHOR]

Flocculation is one of the most widely applied techniques for water treatment and sludge dewatering. A fresh environmentally friendly and powerful flocculant is highly eager in the sludge dewatering area. In this work, a highly efficient cationic flocculant, chitosan-g-PDMDAAC was synthesized through grafting a monomer, dimethy ldiallyl ammonium chloride(DMDAAC), onto chitosan initiated by ceric sulfate under ultrasonic-assisted and conventional heating condition. The graft copolymer was characterized using FT-IR, XRD and SEM. Further, the dewatering performance of municipal activated sludge was evaluated by the filter cake moisture content and specific resistance in filtration. Its application as a flocculant for wastewater treatment was investigated. The prepared chitosan-g-PDMDAAC showed a highly effective flocculation capability for activated sludge compared with chitosan, polyacrylamide(PAM), cationic polyacrylamide(CPAM). [ABSTRACT FROM AUTHOR]

The magnetic iron nanoparticles (MFeNp) were biosynthesised using the extract of Cinnamomum tamala (bay leaf) and examined for its efficacy on sludge dewatering. The characteristics of MFeNp were studied using scanning electron microscope (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectrometer (XPS) techniques. The presence of polyphenolic compounds were confirmed by FTIR and XPS analysis. The reduction in capillary suction time (CST) (71.36 to 16.5 s) and specific resistance to filtration (SRF) (53.71 × 10 to 1.47 × 10 m/kg) values have indicated that the use of Fenton nanocatalyst enhanced the sludge dewaterability. The differential scanning calorimetry (DSC) analysis has shown that the mass of bound water in the treated sludge was decreased significantly from 1.45 to 0.92 kg HO/kg DS. The breakdown of extracellular polymeric substances (EPS) by the MFeNp leads to the significant reduction in proteins, polysaccharides, water content and heavy metals. The optimisation using response surface modelling (RSM) have shown that the maximum removal efficiency of water from the sludge was 85.9 % when the optimum pH (3) MFeNp dosage (50 mg/g DS) and HO dosage (500 mg/g DS) were maintained. The experimental results and the statistical optimisation have suggested that MFeNp can be used as a potential nanocatalyst for the sludge dewaterability and hence it can be used for the agricultural purpose. [ABSTRACT FROM AUTHOR]

Sludge treatment reed bed (STRB) systems have been used for dewatering and mineralisation of sludge in Europe since 1988. STRB systems provide substantial environmental, economic, and operational benefits compared to mechanical sludge dewatering solutions such as belt presses and centrifuges. They require less energy, no chemicals, reduce the sludge volume and produce bio solids with dry solid contents up to 20-40% under Danish climate conditions, depending on the sludge quality. Experience has shown that sludge treated in STRBs represents a high quality product with a low content of pathogens and hazardous organic compounds, qualities that make it suitable for recycling on agricultural land. The upfront capital cost for STRBs are often higher compared to mechanical dewatering devices. However, the operational expenses (OPEX) (including energy, chemicals, bio solid handling) are significantly lower compared to conventional mechanical dewatering devices, delivering an economic break-even of about 3-5 years. This paper provides an overview of the operation and maintenance costs and environmental benefits of a typical STRB based on the experiences gained from the operation of a large number of STRBs with yearly treatment capacities between 100 and 3,000 tonnes of dry solid up to approximately 250,000 PE in Denmark and Europe. [ABSTRACT FROM AUTHOR]

Sludge samples taken from different sources and times may have different characteristics that could affect dewatering performance. In this study, 20 sludge samples from five wastewater treatment plants and different seasons in 1 year were characterized. Pearson correlation analysis indicated that solid content (SC), total suspended solid (TSS), polysaccharides and proteins contents had positive correlations with the capillary suction time (CST), whereas volatile suspended-solid/total suspended solid (VSS/TSS) exhibited negative correlations with CST. Moreover, no correlations between CST and specific resistance to filtration were found among these different sludge samples. The principal component analysis confirmed that only two group variables could represent most of the sludge characteristic parameters. The first set of variables represents the particulate nature of the biotic factors (SC, VSS/TSS, SCOD, TSS, polysaccharides and proteins), and the second set is the pH. CST could not be a reasonable indicator of dewaterability in sludge deep dewatering by Fe/SO-phosphogypsum composite conditioning. Furthermore, the results of diaphragm filter press dewatering showed that initial SC and VSS/TSS were the most dominant sludge characteristics affecting the solid content of dewatered cake ( R = 0.610, p = 0.016; R = −0.838, p = 0.000, respectively) with Fe/SO-phosphogypsum composite conditioning. Results from this study suggest that dewatering performance is predictable by sludge characteristics parameters for Fe/SO-phosphogypsum conditioning. [ABSTRACT FROM AUTHOR]

Dewatering of sludge from sewage treatment plants is proving to be a significant challenge due to the large amounts of residual sludges generated annually. In recent years, research and development have focused on improving the dewatering process in order to reduce subsequent costs of sludge management and transport. To achieve this goal, it is necessary to establish reliable indices that reflect the efficiency of sludge dewatering. However, the evaluation of sludge dewaterability is not an easy task due to the highly complex nature of sewage sludge and variations in solid–liquid separation methods. Most traditional dewatering indices fail to predict the maximum cake solids content achievable during full-scale dewatering. This paper reviews the difficulties in assessing sludge dewatering performance, and the main techniques used to evaluate dewatering performance are compared and discussed in detail. Finally, the paper suggests a new dewatering index, namely the modified centrifugal index, which is demonstrated to be an appropriate indicator for estimating the final cake solids content as well as simulating the prototype dewatering process. [ABSTRACT FROM AUTHOR]

Sewage sludge treatment is becoming one of the most significant challenges for domestic wastewater management. Optimization of sludge management for reducing sludge handling cost in wastewater treatment plant is highly demanded. Sludge treatment reed bed system (STRB) is an eco-environmentally friendly technology which has a low investment input and reduced costs for operation and maintenance. The objective of this study is to evaluate the effect of earthworm assistant STRB in terms of sludge dewatering and stabilization of surplus sludge. The results show that draining and evapotranspiration (ET) take the main role for sludge dewatering; with maximum of 77 and 43 % water was removed through draining and ET, respectively. Plants improved ET rate up to 13.1 % in the planted STRB compare with the unplanted STRB. The combination of plants and earthworms increased ET rate of 20.9 % more than the control STRB (unplanted without earthworms). The planted STRB with earthworm reached the lowest water content in accumulated sludge of 46 %. There was a systematic increase of total solids (TS) concentration from 0.5 % in the influent to 25-54 % in the accumulated sludge. Earthworms enhanced the sludge stabilization dramatic with the ratio of volatile solids (VS)/TS decreased from 49 % in the influent to 18 % in the accumulated sludge in the earthworm assistant STRB. The results demonstrated a good efficiency for sludge dewatering and stabilization with the assistant of earthworms in STRBs, which can be an alternative technology for sludge treatment in wastewater treatment plants. [ABSTRACT FROM AUTHOR]

The large-scale blooms of Enteromorpha disrupts normal ecosystem functioning and brought serious environmental problems in past years. This study focused on the recycling of it with the aim of “treating waste by waste.” In this paper, Enteromorpha polysaccharide (Ep) was applied as a new coagulant aid in sludge treatment process. Initially, orthogonal test was conducted and then the effect of Ep on coagulation behavior was studied and coagulation performance was evaluated in terms of solid content, turbidity, filtrate rate, capillary suction time, and resistance to filtration. Zeta potential and scanning electron microscopic (SEM) were also measured to investigate coagulation mechanism. In addition, cost analysis of sludge treatment was also discussed in this paper. Results of orthogonal test showed that coagulation efficiency was significantly affected by hydraulic conditions. Sludge treatment efficiency could be apparently improved by Ep addition and the optimum polyacrylamide (PAM) and Ep dosages were 15 and 3 mg/L, respectively. When Ep was used in combination with PAM, the average particle size of sludge was increased, and the treated sludge possessed better dehydration ability. In addition, results of cost analysis showed that Ep addition could reduce the cost of sludge treatment by reducing PAM dosage. [ABSTRACT FROM AUTHOR]

The hydrophobic cationic chitosan (HTCC) flocculant was synthesized by reacting chitosan with epoxy propyl trimethyl ammonium chloride (EPTAC) and (2,3-epoxy propyl) dodecyl dimethyl ammonium chloride (EDC), to improve its waste sludge dewaterability. By FTIR and1H NMR analysis, EPTAC and EDC were confirmed to be grafted onto the molecular chains of chitosan (CTS) successfully. With the increase of EDC content, G′ of HTCC aqueous solution with 1:1.5:1.5 mole ratio of CTS:EPTAC:EDC consistently showed higher values than G″ over the entire frequency range explored, indicating the formation of a physically cross-linked network. The crystallization ability of HTCC decreased compared with pristine CTS. The long alkyl chains on the EDC molecules enhanced the hydrophobicity of HTCC, and better dewaterability of the waste sludge was achieved through the promoted bridging action of HTCC. [ABSTRACT FROM AUTHOR]

In order to improve the waste sludge dewaterability of polyacrylamide (PAM), composite conditioner of cationic PAM/montmorillonite (CPAM/MMT) was synthesized by in situ polymerization. The structure and property of the composite were studied in terms of intermolecular hydrogen bonding, melting behavior, intercalation behavior, and dewaterability of the waste sludge. The results revealed that the molecular weight and cationic degree of CPAM/MMT composites decreased with the increase of MMT content. The hydrogen bonding between –OH groups of MMT and –NH groups of CPAM was confirmed by Fourier transform infrared spectroscopic analysis, which led to a relatively high elastic modulus values and low tan δ values at 5 wt% MMT content, indicating the possible formation of a physically cross-linked network in aqueous solution for the composite. The melting temperature of the composites presented decreasing trend first and then became higher as the content of MMT increased. The MMT platelets dispersed well with an intercalated state in CPAM matrix as indicated by x-ray diffraction analysis and transmission electron microscopic observation. The addition of MMT reduced the specific resistance to filtration of the waste sludge, with a minimum value being achieved at 5 wt% MMT content, while the ultraviolet transmittance of the supernatant of the waste sludge was also improved, and the turbidity was reduced. This synergistic effect of the two components in the composite through charge neutrality and bridging action of CPAM as well as the adsorption capacity of MMT resulted in an enhanced dewaterability of waste sludge. [ABSTRACT FROM AUTHOR]

Sludge Treatment Reed Beds (STRBs) are widely used in Northern Europe to dewater and mineralize surplus sludge from activated sludge systems used to treat urban domestic sewage. STRBs are low-technology, energy-efficient, and do not require addition of chemicals. They dewater and stabilize the sludge and produce a final product that can be safely used as a fertilizer for agricultural crops. Long-term sludge reduction takes place in the reed beds due to dewatering and mineralization of the organic matter in the sludge. Although, in theory, a simple technique relying largely on natural processes, experience has shown that it is very important to understand and respect the basic design and operation requirements of STRBs. This paper describes the basic design and operation requirements of STRBs, with special focus on pivotal requirements to respect in order to secure proper functioning. Also, the paper summarizes performance experience concerning final dry matter content, degree of mineralization, emission of greenhouse gases, and degradation of micro-pollutants in STRBs. There are still a number of outstanding issues that are not fully understood, particularly in relation to the importance of the sludge quality for the dewatering in an STRB. Therefore, extreme care should be taken when attempting to extrapolate the use of STRBs to applications and regions outside of their ‘normal’ and documented area of application.

High water content in sludge will affect the transportation and subsequent disposal of sludge. Bioleaching is a biological sludge conditioning technology, which can effectively improve the dewatering performance of sludge and reduce the content of heavy metals in sludge. Coal fly ash, as a skeleton builder, can also improve the dewatering performance of sludge. In this study, bioleaching combined with coal fly ash (BL-CFA) process was employed to improve sludge dewatering performance. Based on the results of response surface methodology (RSM), the capillary suction time (CST) and water content (WC) of sludge decreased by 52.27% and 38.92%, respectively. The dewatering effect of BL-CFA is superior compared with single process. For extracellular polymeric substances (EPS), the content of protein and polysaccharide in tightly and loosely EPS (TB-EPS and LB-EPS) of sludge decreased after BL-CFA process, while that in soluble EPS (S-EPS) increased. Three-dimensional fluorescence indicated that the weakened fluorescent areas of proteinoid and soluble microbial by-product-like (SMP) organic in LB-EPS and TB-EPS, which is beneficial to the improvement of sludge dewatering performance. Fourier transform infrared (FTIR) spectroscopy showed that the polysaccharides and proteins in the sludge were cleaved and released into the supernatant after BL-CFA process. The variation of particle size revealed that flocculation occurred after adding CFA into acidified sludge, and a supporting structure was formed in the sludge with the assist of CFA through the analysis of the scanning electron microscopy (SEM). Based on the above results, a triple dehydration mechanism was proposed for BL-CFA process, namely, cracking-flocculation-skeleton construction, which endows the combined process with superior sludge dewatering effect and application potential. [Display omitted] • BL-CFA process is an innovative method to improve sludge dewatering performance. • The mechanism of BL-CFA process can be ascribed as cracking-flocculation-skeleton. • The WC of sludge decreased to 59.20% and CST decreased by 52.27% optimized by RSM. • Heavy metals in sludge can be effectively removed by BL-CFA process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A green and cost-effective sludge dewatering agent SBF was synthesized. • SBF notably decomposed EPS components and changed the protein secondary structure. • Increasing the hydrophobic substance of EPS by 41.6% after SBF conditioning. • Improving sludge dewatering by charge neutralization and hydrophobic association. • SBF conditioning sludge has great application potential in technology and economy. To clarify the effect of extracellular polymeric substances (EPS), protein and hydrophilic substances on the dewatering efficiency during starch-grafted flocculant (SBF) conditioning, a green and cost-saving SBF was synthesized. Dewatering performance of sludge, secondary structure of protein, change of hydrophobic substances and removal of bound water were investigated. Results showed that after SBF conditioning, filter cake moisture content and specific resistance to filtration decreased from 75.63 % and 2.31 × 1012 m/kg to 66.76 % and 5.68 × 1011 m/kg, respectively. SBF neutralized the negative charges from the sludge system, promoting the increase of sludge flocs size and EPS decomposition, decreasing the compressibility of sludge and constructing a channel for water release. Moreover, the secondary structures of protein were changed through the interaction between SBF and the oxygen-containing functional groups in EPS, resulting in the reduction of hydrophilic substances and the increase of hydrophobic substances, which increased the hydrophobicity of molecules and thus improved the dewatering capacity of sludge. Meanwhile, the construction of sludge skeleton channels, charge neutralization, hydrophobic association effect were the primary mechanisms of SBF conditioning sludge dewatering. Additionally, SBF has an excellent economy as a sludge conditioner. This paper provided a new ideal for starch-based flocculants for improving the dewatering capacity of sludge treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The preparation conditions of polysilicate were optimized by single factor and RSM. • PSF, PSAF, and PSAFM were amorphous polymers with high polymerization degree. • PSAFM showed superior performance in sludge dewatering treatment. • The dewatering was due to adsorption bridging and charge neutralization. Coagulation is an extensive and effective pretreatment technology for improving sludge dewatering performance. In this study, polysilicate ferric (PSF), polysilicate aluminum ferric (PSAF), and polysilicate aluminum ferric magnesium (PSAFM) were prepared by copolymerization reaction, and their preparation conditions include pH, temperature (T), and mole ratio were optimized by the single factor and response surface experiments. The optimal preparation conditions of the above coagulants are shown as follows: PSF (pH = 1.0, T = 20 °C, Si/Fe = 1.00), PSAF (pH = 1.0, T = 20 °C, Si/M = 0.40, Fe/Al = 1.562), PSAFM (pH = 1.0, T = 20 °C, Si/M = 1.08, Fe/Al = 2.00, Fe/Mg = 2.00). The characterization of dewatering agents was analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and Fe-Ferron time-by-time complexation colorimetric method. Also, the particle sizes, molecular weights and Zeta potentials were analyzed. The results indicated that Fe3+, Al3+, Mg2+ and polysilicon acid underwent polymerization to form macromolecular amorphous polymers. The performance of polysilicate in sludge dewatering pretreatment were investigated by coagulation experiments, meanwhile, in order to study the influence of polysilicic acid on sludge dewatering performance, commercial polyferric sulfate (PFS) was taken as a comparison. The results showed that polysilicate improved sludge dewatering performance through adsorption bridging effect and charge neutralization. In addition, the content of tightly bound EPS (TB-EPS) and bound water was reduced by polysilicate, which resulted in excellent sludge dewatering performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • With PbO 2 electrode, higher reduction, dewatering and cell-breaking was achieved. • Quantified results show that indirect oxidation plays a major role in cell breaking. • OH related oxidation presented the highest contribution to the sludge treatment. • PbO 2 electrodes modified with RGO can improve the ·OH yields. • Adding Cl- can improve the effect of electrochemistry on sludge cell-breaking. In this study, a PbO 2 plate electrode was synthesized and optimized for the electrochemical treatment application of waste activated sludge from a municipal wastewater treatment. The sludge dewaterability and mass reduction with different electrolysis time and voltage were quantified to evaluate the treatment efficiency. The mechanism of cell breaking was studied by evaluating different electrochemical oxidation pathways. Results showed that the electrochemical treatment at a voltage of 25 V and electrolysis time of 120 min improved the dewaterability of the sludge by 35.9%, and the concentration of mixed liquor suspended solids (MLSS) was reduced by 33.7%. Using Scanning Electron Microscope (SEM) and Cell fluorescence staining experiments, the impact on the integrity of sludge cells was evaluated. Results showed that electrochemical process clearly destroyed the sludge cell structure and lead to the cell death. Further investigation revealed that hydroxyl radicals (·OH) and sulfate radicals (SO 4 ·-) produced during the electrochemical treatment played a major role in the cell wall-breaking, while chloride ions (Cl-) in the electrolyte significantly enhanced the effect due to formation of chloride-related oxidants. The PbO 2 electrode was modified by chemically reduced graphene oxide (RGO) to improve the ·OH production capacity. Results showed that the PbO 2 (0.05 RGO by wt.%) electrode had the highest ·OH production rate (81.7 μmol/(cm2·min)). The electrode improved the removal of MLSS and MLVSS by 11.3% and 11.5%, respectively. And the sludge dewatering and cell destruction were enhanced by 7% and 15.1%, respectively. Adding more NaCl was confirmed as an effective method to improve the electrochemical performance of sludge treatment mainly due to the higher content of active Cl- species formed. [ABSTRACT FROM AUTHOR]

Over the past years, persulfate (PS) is widely applied due to their high versatility and efficacy in decontamination and sterilization. While treatment of organic chemicals, remediation of soil and groundwater, sludge treatment, disinfection on pathogen microorganisms have been covered by most published reviews, there are no comprehensive and specific reviews on its application to address diverse sustainability challenges, including solid waste treatment, resources recovery and regeneration of ecomaterials. PS applications mainly rely on direct oxidation by PS itself or the reactive sulfate radical (SO 4 •− ) or hydroxyl radical ( • OH) from the activation of peroxodisulfate (PDS, S 2 O 8 2 − ) or peroxymonosulfate (PMS, HSO 5 − ) in SO 4 •− -based advanced oxidation processes (SO 4 •− -AOPs). From a broader perspective of environmental cleanup and sustainability, this review summarizes the various applications of PS except pollutant decontamination and elaborates the possible reaction mechanisms. Additionally, the differences between PS treatment and conventional technologies are highlighted. Challenges, research needs and future prospect are thus discussed to promote the development of the applications of PS-based oxidation processes in niche environmental fields. In all, this review is a call to pay more attention to the possibilities of PS application in practical resource reutilization and environmental protection except widely reported pollutant degradation. [Display omitted] • SO 4 •−-AOPs have diverse applications except for conventional pollutant degradation. • The proper dispose of typical biomass by SO 4 •−-AOPs is discussed. • The unexpected plastic flotation for PVC separation can be realized by SO 4 •−-AOPs. • Recycling of base or precious metals from e-waste and minerals is presented. • The regeneration of ecomaterials can be achieved by SO 4 •−-based AOPs. [ABSTRACT FROM AUTHOR]

• The cellulose content in wastewater of various countries are summarized and discussed. • The degradation and fate of cellulose in activated sludge system are mapped. • Three kinds of cellulose recovery approaches are summarized and compared. • The mechanisms of oxygen reduction after cellulose recovery are thoroughly discussed. • A source separation-based cellulose recovery protocol are proposed. The wastewater treatment plants are transforming to water resource recovery facilities. The essence behind this transformation is to recover resources from wastewater as much as possible instead of destroying and removal. By far, a wide array of products (energy, fertilizer, etc.) in wastewater and recovery technologies have been identified. However, only a few technologies have been extrapolated into full-scale practices. Herein, cellulose is such a kind of resource originating from toilet paper and its recovery has been implemented and endorsed by research efforts in terms of environmental and economic favourability. This review aims to comprehensively map the technologies of cellulose recovery from wastewater and clarify the associated internal impact and external market potential. First, the source, fate, and transformation of cellulose in a typical WWTP (applying activated sludge) are analyzed to provide a holistic overview of the recovery potential and points. Second, cellulose recovery technologies are reviewed and summarized in a historical timeline with an emphasis on rotating belt filters. Particularly, the impacts of cellulose recovery on wastewater treatment performance and the valorization routes are introduced and discussed comprehensively to make the benefits more explicit. The third section of the review presents a discussion in terms of sustainability and some other factors/routes to manage toilet paper and cellulose. Considering the mature value chain, versatile application routes, and favorable environmental impact, cellulose recovery is highly recommended to be included in wastewater management. [Display omitted] [ABSTRACT FROM AUTHOR]