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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]

Extracellular polymeric substances (EPS) are a critical influencing factor in sludge dewatering. Disrupting such EPS contributes to the release of bound water in sludge, enhancing the sludge dewatering performance. In This study, quaternized straw fibers that are destructive to the EPS structure and components in active sludge were prepared useing heterogeneous free radical graft polymerization. Straw fibers, dimethyl diallyl ammonium chloride (DMDAAC), ammonium persulfate (APS), and acrylamide (AM) were taken as the substrate, grafting monomer, catalyst, and cross-linking agent, respectively.The optimal processing conditions determined for the DMDAAC-based quaternization and graft modification of straw fibers were as follows: reaction temperature of 60 °C, reaction time of 5 h, 0.100 g of catalyst APS dosage per gram of straw, and 3.000 ml of DMDAAC dosage per gram of straw. The optimal processing conditions yielded 1.335 g of modified straw fibers per gram of straw, 33.67% grafting rate, and 31.70% substitution of the quaternary ammonium groups. The capillary suction time (CST) was conditioned from 243.3 ± 22.6 s in the original sludge to 134.5 ± 34.45 s. The specific resistance to filtration (SRF) was reduced from 8.82 ± 0.51 × 1012 m/kg in the original sludge to 4.59 ± 0.23 × 1012 m/kg. HIGHLIGHTS Modification of straw fiber by quaternary amination grafting can improve sludge dewatering performance.; Modified straw fiber improves sludge dewatering capacity by absorbing EPS.; Modified straw fiber can damage the stability of sludge floc.; Modified straw fiber provides a skeleton structure in the sludge for water removal from the sludge.;

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]

In order to improve the dewatering performance of waste activated sludge，iron-based sludge biochar（Iron-SBC） activating persulfate（PDS） was used to treat sludge. The effects of PDS dosage，Iron-SBC dosage，reaction time，reaction temperature and initial pH on waste activated sludge dewatering efficiency were studied，and the mechanism was also analyzed. The results showed that when the temperature was 65 ℃，the dosage of PDS per unit TSS was 150 mg/g，the dosage of Iron-SBC per unit TSS was 350 mg/g，the initial pH was 6.68，after being conditioned by Iron-SBC/PDS for 20 minutes，the sludge capillary water absorption time，sludge specific resistance and sludge cake moisture content decreased to 8.4 s，5.4×1012 m/kg and 73.5%，respectively. The mechanism analysis indicated that oxidation reaction occurred during the process. The originally tight and flat sludge flocs and extracellular polymers were cracked and the bound water was released. The highly hydrophilic tightly bound extracellular polymeric substances（TB-EPS） in sludge were transformed into loosely bound extracellular polymeric substances（LB-EPS） and soluble extracellular polymeric substances（S-EPS），and the proteins which were unfavorable to sludge dewatering were oxidized and degraded. The decrease of TB-EPS and neutralization of positive iron ions increased the Zeta potential value. Iron-SBC with rigid structure reduced the compressibility coefficient of sludge cake. At the same time，under the flocculation of Fe3+，the fractal dimension of sludge became larger. Under the coupling action of “oxidation-skeleton construction”，the waste activated sludge deep dewatering was realized.

The reclaimed water of municipal sewage plant after advanced treatment in a power plant is used as makeup of circulating water system. Due to the problems in the advanced treatment system of reclaimed water，such as the output of the mechanical acceleration clarification tank failing to reach the designed value，poor effluent quality，the sludge dewatering system failing to operate normally，the feeding blockage of the lime system，the widespread leakage of the dosing device and no chain control，etc.，the requirements for normal use of reclaimed water in the power plant can’t be met. After the diagnosis of the problems，the optimization scheme was put forward. The internal structure of the mechanical acceleration clarification tank and the bottom sludge discharge pipeline system were modified respectively to restore the processing capacity of the mechanical acceleration clarification tank and meet the requirements of the water required of the system. The sludge dewatering system was modified to restore the sludge dewatering unit. The lime dosing system was modified to improve the problems of lime dosing and material blockage then restored the stable operation of the lime system. After optimization and transformation，the output of the clarification tank was improved，and the effluent quality of the system was optimized，effectively ensuring the normal operation of the deep treatment system for recycled water and the safety of water use in the power plant.

Dewatering is a crucial stage in the treatment of sludge since it directly increases capacity and lowers the cost of subsequent handling. Enhanced dewatering of printing and dyeing sludge was experimentally investigated with combined conditioners of sludge-derived biochar and ferric chloride (FeCl3) in this study. Results showed that the optimal conditioner dosages were: FeCl3 of 3% dry sludge (DS) and biochar of 60% DS. Compared with raw sludge, the sludge specific resistance to filtration (SRF) decreased by 77.14%, and the moisture content of sludge decreased from 85.38% to 67.08%. In addition, the chemical oxygen demand (COD), turbidity and chromaticity of supernatant decreased by 32.50%, 89.20% and 77.50%, respectively. It was found that the synergistic effect existed between the two conditioners. The possible mechanism was that FeCl3 aggregated small sludge particles to form large flocs and improved the dewatering performance of sludge, while biochar helped to build an incompressible and permeable sludge cake to further improve the sludge dewaterability due to its relatively hydrophobicity and large specific surface area. Therefore, combined addition of FeCl3 and biochar might be a promising conditioning method to enhance textile sludge dewaterability. [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]

Focusing on dewatering technologies for coal-containing sludge in the coal chemical industry・ With technological advances, dewatering methods are shifting from traditional techniques to combined treatments combining multiple techniques, aiming to improve dewatering efficiency by dissolving extracellular polymers (EPS)・ The article analyzes the characteristics of coal・containing sludge, treatment difficulties, and points out the key issues to be addressed in future research: first, optimizing the combined sequence of dewatering technologies and method selection; second, clarifying the impact of combined deep dewatering on sludge energy use, resource recovery, and material manufacturing; and third, perfecting the multifaceted evaluation system of coal-containing sludge dewatering processes・ It is recommended to adopt the life cycle assessment (LCA) method to comprehensively evaluate the carbon emission, environmental impact and cost of sludge treatment, so as to promote the optimization and promotion of coal-containing sludge deep dewatering technology. [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.)

Activated sludge process is one of the most widely used processes for wastewater biological treatment. As the main by-product of activated sludge process，sludge with the high moisture content easily results in various problems such as the difficult transportation，high cost of resource utilization，and low calorific value. Therefore，it is necessary to conduct the sludge dewatering. Flocculation is widely used in sludge dewatering due to its unique advantages including simple operation，fast reaction rate，extensive application scope and excellent dewatering performance. The composition，advantages and disadvantages，and related flocculation mechanisms of various flocculants are introduced in detail. Subsequently，the preparation strategies of various flocculants and their application in sludge dewatering are systematically summarized. Finally，the outlooks of various flocculants on sludge dewatering are presented in order to provide a reference for future research on the application of flocculation technology on sludge dewatering.

Using electrolytic zero-valent iron-activated sodium hypochlorite (EZVI-NaClO) to pretreat sludge, the capillary suction time (CST) was utilized to evaluate sludge dewaterability. Ammonia nitrogen (NH4-N), dissolved phosphorus, and total phosphorus in the supernatant were used to analyze sludge disintegration. This approach aimed to evaluate the effectiveness of the pretreatment process and its impact on the sludge composition. The migration and transformation of extracellular polymeric substances (EPS), including dissolved EPS (S-EPS), loosely boundEPS, and tightly bound-EPS (TB-EPS), were analyzed by detecting protein and polysaccharide concentrations and three-dimensional fluorescence excitation-emission spectroscopy (3D-EEM). The sludge particle properties, including sludge viscosity and particle size, were also analyzed. The results suggested that the optimal pH value, NaClO dosage, current, and reaction time were 2, 100 mg/gDS (dry sludge), 0.2A, and 30 min, respectively, with a CST reduction of 43%. Protein and polysaccharide contents in TB-EPS were significantly reduced in the EZVI-NaClO group. Conversely, protein and polysaccharides contents in S-EPS increased, suggesting that EZVI-NaClO treatment could disrupt the EPS. Besides, the viscosity of the treated sludge decreased from 195.4 to 54.9 mPa·S, indicating that sludge fluidity became better. ZEVI-NaClO could enhance sludge dewaterability by destructing protein and polysaccharide structure and improving sludge hydrophobicity. HIGHLIGHTS Electrolytic zero-valent iron-activated sodium hypochlorite (EZVI-NaClO)-modified extracellular polymeric substance (EPS) extracted from WAS.; EZVI-NaClO can reduce O = C-NH- that affects protein strength and stiffness.; EZVI-NaClO enhances the flocculation and hydrophobicity of EPS.;

Abstract 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.

This article presents the experience in the field of using ultrasonication as a pre-treatment method of SS. On the basis of a review of the literature, the effect of pretreatment of sewage sludge by US 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. 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.

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.

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]

[Display omitted] • Sludge dewatering extent was enhanced after Fe 3 O 4 -activated H 2 O 2 treatment. • Enhanced mechanism of sludge dewatering by Fe 3 O 4 -activated H 2 O 2 was unveiled. • Fe 3 O 4 -activated H 2 O 2 disrupted sludge EPS and released intracellular water. • Fe 3 O 4 as skeleton builder enhanced sludge floc strength and formed new channels. Homogeneous Fenton (Fe2+/H 2 O 2) serves as a high-efficiency conditioning method for sludge dewatering due to the generation of strong oxidizing hydroxyl radicals (OH). However, high dose of ferric salts produces iron-rich dewatered sludge and decrease sludge organic matters, which will not be conducive to the subsequent disposal and reutilization. Considering advantages of Fe 3 O 4 as heterogeneous Fenton catalyst, Fe 3 O 4 -activated H 2 O 2 (Fe 3 O 4 + H 2 O 2) in this study was adopted to improve sludge deep-dewatering. Reduction efficiency of the bound water (71.3 %) after Fe 3 O 4 + H 2 O 2 treatment (after a reaction time of 30 min) were much higher than those in the Fe2++H 2 O 2 treatment. Especially, the moisture content of treated sludge cake by Fe 3 O 4 + H 2 O 2 remarkably decreased from 86.4 % to 61.3 %. Improvement mechanism of sludge dewatering after Fe 3 O 4 + H 2 O 2 treatment mainly included electrostatic neutralization, reactive radical oxidation, and skeleton building by analysis of contribution factors. The generation of H+ in acidification could neutralize the negatively charged compounds to promote sludge hydrophobicity. Meanwhile reactive radicals generated from Fe 3 O 4 + H 2 O 2 destroyed sludge extracellular polymeric substances and cell structure to release intracellular water. Furthermore, Fe 3 O 4 as a skeleton builder could reconstruct destructive sludge flocs and form new dewatering channels. Finally, low Fe leaching content and recoverability of Fe 3 O 4 effectively will decrease environmental implication. [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]

Efficient and sustainable sludge management is a significant environmental and health challenge. Sludge-treatment reed beds (STRBs) are widely recognized as a cost-effective, highly efficient, and environmentally friendly solution for sludge treatment and dewatering. This study investigated the bacterial community composition and diversity in pilot-scale STRBs operating at different sludge loading rates (75, 100, and 125 ​kg ​m2 year−1). 16S rRNA V4 DNA sequencing was used to assess the diversity of the bacterial communities within the sludge samples. The relative abundance of prokaryotic taxa was affected by all treatments. As the sludge loads increased, the Shannon entropy and evenness diversity also increased for the STRBs and unplanted beds. Interestingly, the presence of reeds resulted in significantly lower Shannon and evenness indices than unplanted beds, regardless of the sludge. Additionally, the correlation network analysis revealed distinct microbial clusters with distinct responses to reeds and sludge loads. Principal component analysis evidenced an association between cluster 5 and organic matter decomposition, primarily at higher sludge doses, while clusters 4 and 6 were related to sludge decomposition at lower doses. Additionally, cluster 4 was associated with nutrient removal. The formation of distinct microbial niches was linked to sludge stabilization and nutrient removal and was influenced by both sludge loading rates and the presence of reeds. Future research can leverage these findings to innovate pollutant removal and ecosystem services for sludge treatment, thus advancing sustainable sludge management and environmental preservation.

The decanter-centrifuge is widely used for dewatering and thickening of civil and industrial sludge. The latest generation decanters, both the bowl motors (main) and the screw (back-drive) are often driven by variable-frequency drives (VFD), with the back-drive able to recover the energy during braking. We created a decanter centrifuge energy model equipped with a braking recovery system during the sludge dewatering process, with the aim of identifying its optimal operating conditions for both energy consumption and product quality. Specific models at 15–20–25 m3 h−1 and various differentials speed (Δn) were used to derive a general model, then validated with experiments at 18–20 m3 h−1. Specific models used to identify the best operating conditions in terms of specific energy (e) and energy recovery (ERec) show that at 15–20–25 m3 h−1 the lowest energy consumptions were 1.88–1.76–1.57 kWh m−3, respectively, instead, ERec was 5.88–0.31–12.10 kW respectively, highlighting that a high recovery is not necessarily linked to an increased energy saving. The accuracy of these models was confirmed by high values of correlation coefficients R2 and very low Root Mean Square Errors (RMSE) in each case. The general model, extrapolated from the specific models, makes it possible to predict specific consumptions at different flow rates within the operating range of the decanter. This was validated with an experimental test at 18–20 m3 h−1 with R2 above 97 % and RMSE 2,59E-02 kWh m3. The dry matter content in the cake decreases when the Δn or the feed rate increases.In conclusion, the decanter centrifuge model could represent a useful tool for optimizing the sludge dehydration process.

Managing high water content sludge in wastewater treatment is crucial for sustainability. This involves a complex challenge of maximizing the removal of loosely bound extracellular polymeric substances (LB-EPS) while minimizing ultrasonic-Fenton process costs. This study introduces a novel approach to address these conflicting objectives by adopting fuzzy multi-objective optimization. This method reconciles the conflicting objectives by identifying the optimal conditions for ferrous ion (Fe2+) dosage, hydrogen peroxide (H2O2) dosage, and ultrasonication time. The optimization model incorporates empirical equations that define the effects of Fenton’s reagent and ultrasonication on LB-EPS removal, as well as considerations for material and electricity usage costs and the cumulative uncertainties associated with experimental runs. To effectively capture the trade-offs between EPS removal and process costs, the ɛ -constraint method was utilized to delineate the Pareto front. This approach significantly enhances LB-EPS removal from anaerobically digested sludge and establishes boundary limits within the Pareto front for practical application within the context of fuzzy optimization. The optimized solution derived from this innovative approach resulted in the conditions of 10 mM Fe2+dosage, 100 mM H2O2 dosage, and 10 min of ultrasonication. This configuration achieves an impressive 60.7% ± 3.7% LB-EPS removal while maintaining a cost of 26.6 USD/L and ensuring 100% overall satisfaction. This research represents a significant advancement in sludge dewatering strategies. It underscores the pivotal role of innovative decision-making approaches in advancing the field of sludge dewatering methodologies for more sustainable wastewater treatment practices.

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.

This study was conducted on the feasibility of improving processes of thickening, anaerobic digestion, and sludge dewatering at wastewater treatment plants on a laboratory pilot scale, aiming to reduce polyelectrolyte consumption by 50% and replace it with chemical sludge. Parameters of Sludge Volume Index (SVI), Specific Filtration Resistance (SRF), compressibility coefficient, filtration rate, and biogas production rate were investigated. It is shown that by applying 200 mg/g of water treatment plant sludge to wastewater sludge, the compressibility coefficient was decreased by 27%, the filtration rate was increased by 70%, and SVI and SRF were decreased by 64.9% and 43.3%, respectively. Therefore, it has facilitated the sludge sedimentation and release of its free water. On the other hand, adding the sludge from a water treatment plant led to the proper access of microorganisms to micronutrients and improvement of their performance resulting in an increase of 7.77% in the total biogas production. The iron present in the digestion process caused an increase in biogas production by increasing the activity of enzymes, reducing oxidation-reduction potential, and improving the direct interspecies electrons transfer. In conclusion, adding the optimal amount of water treatment plant sludge, along with the environmental management of a meaningful portion of water and wastewater residuals, may play an important role in significantly reducing polyelectrolyte consumption and improving biogas production.

Variation of the digester temperature during the year enables the operation of digesters as seasonal heat storage contributing to a holistic heat management at water resource recovery facilities. Full‐ and lab‐scale process data were conducted to examine the effect of the digester temperature on process stability, sludge liquor quality, and dewaterability. Both full‐ and lab‐scale digesters show a stable anaerobic degradation process with a hydraulic retention time of more than 20 days and organic load rates up to 2.2‐kg COD/(m3·day) at temperatures between 33 and 53°C. The concentrations of soluble COD and ammonium‐nitrogen in the sludge liquor digested at 53°C are 2.6 to 5.8 times and 1.3 times higher, respectively, than in the sludge liquor digested at 37°C. Dewatering tests show an enhancement of the dewaterability but a clear increase in the polymer demand at increased digester temperature. Practitioner Points: Digesters can operate as seasonal heat storage within mesophilic and thermophilic temperaturesStable anaerobic degradation process for HRT above 20 daysMaintenance of process stability as well as quantity and quality of biogasIncrease of soluble COD in sludge liquor at higher temperaturesBetter dewaterability but higher demand for polymers with increasing temperature [ABSTRACT FROM AUTHOR]

To reduce the water content and improve the incineration characteristics of sludge, rice husk and thermal hydrolysis were employed in this study. Effects of rice husk and thermal hydrolysis on the characteristics of the sludge were investigated. The results showed that synergistic thermal hydrolysis with rice husk could effectively destroy sludge particles and release more bound water. For rice husk with a particle size of 50-mesh and an additional amount of rice husk at 1:0.2, the solid content of the sludge was reduced from 17.4 to 16.2%, and the sludge particle size was reduced by 6%. Filtration time and specific resistance to filtrate (SRF) were shortened by 88.9 and 98.7%, respectively. The organic matter content of the filtration cake increased by 14%, compared with the sludge treated by thermal hydrolysis without rice husk. Furthermore, it could be shown that the most optimal conditions were rice husk of particle size 50-mesh and an additional amount of rice husk at 1:0.2, which could lead to effective thermal hydrolysis and higher organic matter content of the filtration cake. HIGHLIGHTS The optimal process of collaborative thermal hydrolysis of rice husk was selected by changing the grain size and the additional amount of rice husk.; Good drainage channels can be formed in the dehydration process of rice husk after the thermal hydrolysis of sludge to improve the efficiency of dehydration.; Rice husk combined with thermal hydrolysis can improve the organic matter content of sludge-dehydrated filter cake.;

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]

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

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.

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]

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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]

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.

Sludge treatment and disposal processes in wastewater treatment plants account for a significant portion of the total treatment costs. One of the most expensive parts of sludge treatment is chemical conditioning. Study of the effect of process chain on the conditioning and dewaterability can effectively optimize and reduce operating costs and increase the quality of effluent sludge. This paper investigates the impact of aerobic digestion of waste sludge in Yazd wastewater treatment plant by SBR method on its dewaterability. For this purpose, the waste sludge sample of the plant was aerated in the laboratory at different residence times from 1.5 to 7 days. Then the dewaterability of the sludge was measured by two methods of Specific Resistance to Filtration (SRF) and Tests of Time of Filtration (TTF) in two cases with and without chemical conditioning with cationic polyacrylamide. The results showed that sludge aeration for up to 3 days without conditioning led to the best sludge dewaterability. The best results were obtained at 1.5 days aeration for the conditioning mode with polymer, which improved the dewaterability up to 4.5 times in the optimum polymer dosage. In this case, the polymer dosage decreased by 30% compared to the non-aerated conditioned sludge. It indicates the effect of digestion retention time on dewaterability. At the beginning of the process, the decomposition of cellular material improves the release of water from solid particles. Still, its continuation reduces the dewatering capability due to reduced particle size and conversion to colloidal materials.

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]