SCIENCE OF THE TOTAL ENVIRONMENT
·
2019
·
IF 5.589
Dongdong Ge,Haiping Yuan,Jiamu Xiao,Nanwen Zhu
Tannic acid (TA), a phenolic compound , may be considered as a sludge conditioning agent on account of its ability to precipitate protein. In this study, the effectiveness of TA conditioning on enhancing waste activated sludge (WAS) dewatering was investigated at various pH values. The results indicated that with the conditioning of 0.15 mmol TA per gram of total solid (TS), the WAS dewaterability was affected distinctly by the pH regulation. The reductions of 86.8% capillary suction time (CST), 96.3% specific resistance of filtration (SRF), and 23.6% water content (Wc) of dewatered sludge cake were achieved at an optimal pH value of 4.0. Meanwhile, obvious alterations were observed in some aspects like supernatant viscosity, zeta potential , particle size and extracellular polymeric substances (EPS) polymers. Correlation analysis indicated that the proteins in slime EPS and loosely bound EPS dominantly governed sludge dewaterability. Fluorescence quenching analysis indicated that in the range of acidity, the increase of pH value afforded more binding sites of sludge EPS for TA. However, the removal of EPS protein depended on the combined effect of TA conditioning and pH regulation. The findings provided a novel approach and explanation of WAS dewaterability enhancement using organic additive conditioning and pH regulation.
研究领域:
环境科学
·
污水处理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
WATER RESEARCH
·
2018
·
IF 7.051
Keke Xiao,Kangyue Pei,Hui Wang,Wenbo Yu,Sha Liang,Jingping Hu,Huijie Hou,Bingchuan Liu,Jiakuan Yang
Fenton's reagent has been widely used to enhance sludge dewaterability. However, drawbacks associated with hydrogen peroxide (H 2 O 2 ) in Fenton's reagents exist, since it is a hazardous chemical and shows carcinogenicity , explosivity, instability, and corrosivity. Moreover, initial acidification and subsequent neutralization are needed as optimal conditions for homogeneous Fenton conditioning and final filtrate discharge. In this study, a Fenton-like process for the enhanced dewaterability of waste activated sludge with in-situ generation of H 2 O 2 and without extra pH adjustment was firstly proposed, namely citric acid (CA)-assisted oxygen activation in an air/nano zero-valent iron (nZVI) system and chemical re-coagulation with polydiallyldimethylammonium chloride (PDMDAAC). Using the response surface methodology (RSM), the optimal doses of CA, nZVI, and PDMDAAC were determined to be 13, 33, and 9 mg g −1 dry solids (DS), respectively. This composite conditioner showed a good dewatering capability compared with the raw sludge, e.g. the capillary suction time decreased from 130.0 to 9.5 s. The enhanced sludge dewaterability was further confirmed by laboratory-scale diaphragm filter press dewatering tests, which produced a lower cake moisture content compared with the raw sludge, and the final pH of the filtrate was close to neutrality. The citric acid promoted the production of H 2 O 2 and Fe(II)/Fe(III) species, the degradation of protein in tightly-bound extracellular polymeric substances, and the decomposition of protein-N in the solid phase of sludge, resulting a greater conversion of bound water to free water. The results of electron spin resonance indicated that the hydroxyl radicals were mainly responsible for the decomposition of proteinaceous compounds. The subsequent chemical re-coagulation with PDMDAAC can make the zeta potential of sludge samples less negative, reduce the repulsive electrostatic interactions, and agglomerate the smaller particles into larger aggregates, thus enhancing sludge dewaterability.
研究领域:
环境科学
·
污水处理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF ENVIRONMENTAL MANAGEMENT
·
2022
·
IF 8.91
Xiao Ling,Minjie Chen,Anhong Cai,Honglei Sun,Shanlin Xu,Lei Wang,Xueyan Li,Jing Deng
The dewaterability of waste-activated sludge (WAS) has been extensively examined using zero-valent iron (ZVI)-based advanced oxidation processes (AOPs). However, the high dosage and low utilization efficiencies of ZVI cast doubt on the dependability and viability of ZVI-based AOPs. In this study, we successfully demonstrated pre-magnetization as an efficient, chemical-free, and ecological method for improving the efficiency of sludge dewatering by ZVI/persulfate (PS) process, in which the reduction ratios of capillary suction time (CST) and specific resistance to filtration (SRF) increased by 8.67% and 11.06% under optimal conditions, respectively. The highly active Fe 2+ released during ZVI corrosion may be more essential than ZVI itself during PS activation, which could be strengthened by pre-magnetization. Both homogeneous and heterogeneous Fe 2+ could react with PS to produce aqueous hydroxyl radicals (∙OH) and sulfate radicals (SO 4 − ∙) as well as surface-bound ∙OH and SO 4 − ∙, further decomposing bound-extracellular polymeric substances fractions, broking hydrophilic functional groups and compounds, altering protein secondary structure to expose more hydrophobic sites, and releasing abundant EPS-bound water. Due to the protection of tightly-bound extracellular polymeric substances (TB-EPS) and the competitive oxidation of organics released during the early disintegration stage, radical oxidation primarily occurs at extracellular levels, releasing a bit of intracellular water. Besides, polysaccharides in TB-EPS may function a more significant role in flocculation than proteins, and a porous structure favorable to drainage will be formed after the pre-magnetized ZVI/PS treatment. The cost-benefit analysis further reveals that the Pre-ZVI/PS process presents high reusability and utilization, making it potential for particle application in sludge dewatering.
研究领域:
环境科学
·
污水处理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Scientific Reports
·
2023
·Vol. 13
·期 1
·1-16
·
IF 4.6
Shen Shaohang,Wei Hua,Pan Yu,Hu Pan,Yang Hu
Coagulation/flocculation is one of the most widely used and cost-effective pretreatment methods for improving the dewaterability of sludge. In this study, a cationic modified starch-based flocculant (St-CTA) in conjunction with a popular clay, attapulgite (ATP), was used for the conditioning of waste-activated sludge. The dewatering properties, including the filter cake moisture content, filtration specific resistance, capillary suction time, filtration rate and compressibility coefficient, were measured and compared by varying the doses of St-CTA and ATP. By combination of the apparent dewatering performance and the changes in the contents and distributions of the extracellular polymeric substance (EPS) fractions and components, sludge flocs, and microstructures of sludge cakes, the dewatering mechanisms were discussed in detail. St-CTA in conjunction with ATP can exhibit an enhanced dewaterability of sludge and the water content in final sludge cake can be stably reduced below 80% owing to the synergistic effects of St-CTA and ATP. In addition to the efficient charge neutralization of St-CTA, ATP not only acts as a skeleton builder in the sludge dewatering process which makes the sludge flocs more compact and improves the filterability and permeability, but also tightly interacts with the proteins in EPS of the sludge which reduces the protein content and further enhances the dewatering effect. This study provides an economical, green, and effective way to further improve the dewaterability of sludge.
研究领域:
环境科学
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污水处理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Environmental Sciences
·
2020
·
IF 4.302
Xiaoyang Fan,Yili Wang,Daxin Zhang,Yajie Guo,Shihui Gao,Enrui Li,Huaili Zheng
The effects of four conditioning approaches: Acid, Acid-zero-valent iron (ZVI)/peroxydisulfate (PMS), Fe(II)/PMS and ZVI/PMS, on wastewater activated sludge (WAS) dewatering and organics distribution in supernatant and extracellular polymeric substances (EPS) layers were investigated. The highest reduction in bound water and the most WAS destruction was achieved by Acid-ZVI/PMS, and the optimum conditions were pH 3, ZVI dosage 0.15 g/g dry solid (DS), oxone dosage 0.07 g/g DS and reaction time 10.6 min with the reductions in capillary suction time (CST) and water content (Wc) as 19.67% and 8.49%, respectively. Four conditioning approaches could result in TOC increase in EPS layers and supernatant, and protein (PN) content in tightly bound EPS (TB-EPS). After conditioning, organics in EPS layers could migrate to supernatant. Polysaccharide (PS) was easier to migrate to supernatant than PN. In addition, Acid, Acid-ZVI/PMS or Fe(II)/PMS conditioning promoted the release of some polysaccharides containing ring vibrations v P O, v C-O-C, v C-O-P functional groups from TB-EPS. ESR spectra proved that both radicals of SO 4 - · and ·OH contributed to dewatering and organics transformation and migration. CST value of WAS positively correlated with the ratios of PN/PS in LB-EPS and total EPS, while it negatively correlated with TOC, PN content and PS content in TB-EPS, as well as PS content in supernatant and LB-EPS. BWC negatively correlated to zeta potential and TOC value, PN content, and HA content in supernatant.
研究领域:
环境科学
·
污水处理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2020
·
IF 5.774
Dongdong Ge,Jiamu Xiao,Chang Bian,Haiping Yuan,Nanwen Zhu
Waste activated sludge (WAS), as a kind of hydrophilic colloid substance, is still a major technical challenge in wastewater treatment industry. For enhancing WAS dewaterability, the approach of tannic acid (TA)/Fe 3+ conditioning was verified to be feasible. During conditioning, sludge extracellular protein decreased pronouncedly. Fluorescence quenching analysis revealed that Fe 3+ reduced the binding sites of extracellular polymeric substances available for TA, and the formed TA-Fe 3+ complexes possibly promoted TA aggregates’ settlement and compression. Sludge supernatant viscosity, absolute value of zeta potential and pH value also decreased distinctly, and sludge particle size became larger than that of raw sludge or Fe 3+ -conditioned sludge. Scanning electron microscope suggested that sludge surface morphology became more compacted and denser after TA/Fe 3+ conditioning, which was helpful for the release of water trapped in sludge bio-polymeric network. With 0.15 mmol/gTS TA and 0.9 mmol/gTS Fe 3+ conditioning, sludge capillary suction time, specific resistance of filtration and water content of dewatered sludge cake were decreased by 76.3%, 94.7% and 13.5%, respectively. The findings not only shed new light on the means of applying natural plant organic polymer coupled with inorganic cation to promote WAS dewaterability but offered a potentially theoretical principle of the utilization of plant waste containing TA in WAS treatment.
研究领域:
环境科学
·
污水处理
✓ 已验证
DOI
高影响因子
JOURNAL OF ENVIRONMENTAL MANAGEMENT
·
2021
·
IF 6.789
Yanting Dong,Yanwen Shen,Dongdong Ge,Chang Bian,Haiping Yuan,Nanwen Zhu
Sludge dewatering is necessary to reduce the volume of sludge for cost-effective transport and ultimate disposal. In this study, a novel combined chemical conditioning process was proposed to improve sludge dewatering performance in which sludge flocs were destructed by sodium dichloroisocyanurate (DCCNa) and re-flocculated by Al 2 (SO 4 ) 3 and the mechanism was elucidated. The results showed that sludge capillary suction time (CST) dropped to 15.4 s and moisture content of dewatered sludge cake (Mc) deceased to 71.01% respectively, after the application of combined conditioning with the optimal dosage of 200 mg DCCNa/g dry solids (DS) and 80 mg Al 2 (SO 4 ) 3 /g DS. With chemical conditioning, sludge physicochemical properties were greatly changed. With the DCCNa application, the percentage of low-molecular-weight substances in soluble extracellular polymeric substances (S-EPS) increased. Also, the sludge zeta potential dropped from −16.85 mV to −25.45 mV and the median particle size (D50) decreased from 54.1 μm to 51.6 μm. However, the subsequent conditioning by Al 2 (SO 4 ) 3 dosing not only led to an increment of 18% in the portion of macromolecules in S-EPS, but also increased the zeta potential and D50 to −10.74 mV and 53.2 μm, respectively. The bound water content in sludge declined from 2.92 g/g DS to 1.98 g/g DS after combined conditioning. We concluded that DCCNa disintegrated the sludge flocs and microbial cells leading to the release of bound water, fine particles and organic substances with negative charge, and the fine colloidal particles can be flocculated into large dense aggregations with the dosing of Al 2 (SO 4 ) 3 . In summary, the proposed combined conditioning provided a highly effective and environmental friendly approach to improve the sludge dewatering performance.
研究领域:
环境科学
·
污水处理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Lian Zhang,Wei Fang,Panyue Zhang
The high water content of sewage sludge presents a significant challenge for its subsequent treatment. With activation of hypochlorite treatment hydrophilic protein in sludge could not be effectively degraded which limits the performance of sludge dewatering, meanwhile, excessive radicals could be consumed. To solve this issue, in this study a novel Fe 2+ /Ca(ClO) 2 /tannic acid (TA) process was proposed for the first time, aiming at enhancing the dewaterability of waste activated sludge (WAS). Treatment with 1.2 mmol/g total solids (TS) of Ca(ClO) 2 , 1.0 mmol/g TS of Fe 2+ and 0.15 mmol/g TS of TA resulted in the reduction of 66.58 %, 88.31 % and 9.75 % in capillary suction time (CST), specific resistance to filtration (SRF) and water content (Wc) of sludge cake, respectively. Mechanistic investigations revealed that the ·OH and ·CH 2 CH 2 OH generated within the Fe 2+ /Ca(ClO) 2 /TA system facilitated the decomposition of extracellular polymeric substances (EPS) and sludge cells, leading to the release of bound water as free water. The value of α-helix/(β-sheet + random coil) with Fe 2+ /Ca(ClO) 2 /TA conditioning decreased from 50.43 % to 38.72 %. Furthermore, the formation of multivalent ions, such as Fe 3+ and Ca 2+ , along with TA, promoted re-coagulation, resulting in an increase in sludge particle size and enhanced flocculation. Additionally, TA effectively complexed hydrophilic proteins, facilitating the interaction between calcium and sulfate ions to form additional gypsum material as skeleton in sludge cake, which led to improved permeability and compressibility of the sludge cake. This study provides a new approach for efficient improvement in sludge dewaterability.
研究领域:
环境科学
·
污水处理
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ENVIRONMENTAL MANAGEMENT
·
2021
·
IF 6.789
Guanjun Wang,Dongdong Ge,Lu Bai,Yanting Dong,Chang Bian,Jiajia Xu,Nanwen Zhu,Haiping Yuan
Sludge dewatering , as one of the most important steps of sludge treatment , can facilitate transportation and improve disposal efficiency by reducing the volume of sludge . This study investigated the effects of electrolysis-activated persulfate oxidation on improving sludge dewaterability. The results indicated that the sludge capillary suction time (CST) and water content of dewatered sludge cake (Wc) reduced from 93.7 s and 87.8% to 9.7 s and 68.3% respectively at the optimized process parameters: electrolysis voltage of 40 V, electrolysis time of 20 min, and 1.2 mmol/g TS S 2 O 8 2− . Correlation analysis revealed that the enhancement of sludge dewaterability was closely associated with the increased floc size and zeta potential , decreased protein content in three-layers extracellular polymeric substances (EPS) and viscosity ( R = −0.868, p = 0.002; R = −0.703, p = 0.035; R ≥ 0.961, p < 0.001; R = 0.949, p < 0.001). Four protein fluorescence regions in EPS were analyzed by three-dimensional excitation-emission matrix parallel factor (3D-EEM-PARAFAC). The protein secondary structure was changed after the treatment, and the reduction of α-helix/(β-sheet + random coil) indicated that more hydrophobic sites were exposed. Analysis by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and rheological test demonstrated that the hydrophilic functional groups of the sludge were decreased and the sludge mobility was significantly enhanced after the treatment with electrolysis-activated persulfate oxidation. Moreover, bound water was converted to free water during SO 4 · − and ·OH generated by electrolysis-activated persulfate degraded EPS and attacked sludge cells. Meanwhile, scanning electron microscopy (SEM) images revealed that the treated sludge formed porous channel structures, which promoted the flowability of the water. These findings provide a new insight based on electrolysis-activated persulfate oxidation in sludge treatment for enhancing sludge dewaterability.
研究领域:
环境科学
·
污水处理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Environmental Chemical Engineering
·
2024
·
IF 7.4
Jiali Tan,Ying Huang,Baoyan Chi,Zhenfeng Xiong,Weidong Zhou,Zhuo Yang,Kemei Zhou,Xiaoqing Ruan,Xinxin Duan,Mingzhu Wang,Jun Zhang
Inorganic coagulants are essential agents that can facilitate the sludge deep dewatering, but comprehensive comparative research of commonly used coagulants is lacking. The systematic comparison of six coagulants, including Ferric Chloride (FeCl 3 ), Polymeric Ferrous Sulfate (PFS), Ferrous Sulfate (Fe 2 (SO 4 ) 3 ), Aluminium Chloride (AlCl 3 ), Aluminium Sulfate (Al 2 (SO 4 ) 3 ), and Polymeric Aluminium Chloride (PAC) regarding their performance in conditioning sludge dewatering , physicochemical properties, the risk of heavy metals migration in sludge cake and the mechanism of sludge dewatering, was investigated. Within a dosage range of 20% dry solids (DS), the PFS and FeCl 3 showed a better dewatering effect among the six coagulants, and the water content (Wc) of the sludge cake decreased from 81.2%±1.1% to 57.7%±1.0% and 59.2%±1.6%, respectively. There was a correlation between the pH, zeta potential , viscosity, and bound water content of the sludge and the Wc of the sludge cake during dewatering conditioned by six coagulants. However, there was no correlation between sludge particle size and Wc of the sludge cake. The PFS and FeCl 3 reduced the protein content of tightly bound extracellular polymeric substances (TB-EPS) by 66.1% and 62.6%, respectively. Moreover, the iron coagulants significantly reduced the content of As, Cu, Ni, and Zn in the sludge cake, where the risk levels of As and Ni were largely weakened. The economic analysis shows that iron coagulants were more valuable than aluminium coagulants for engineering applications. Meanwhile, the dewatering mechanisms of the two types of coagulants were revealed. This study provides significant insights into the application of coagulants in engineering practice.
研究领域:
环境科学
·
污水处理
✓ 已验证
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2022
·
IF 16.744
Dongdong Ge,Weixiang Wu,Guangming Li,Yuhui Wang,Guobiao Li,Yanting Dong,Haiping Yuan,Nanwen Zhu
Sludge dewaterability is commonly poor due to the hydrophilic biopolymeric substances. The highly efficient oxidation process is of great significance for extracellular biopolymers disintegration and bound water discharge. This work investigated the novel CaO 2 -enhanced peroxone (CaO 2 /O 3 ) process to adjust sludge characteristics for dewaterability enhancement and focused on the molecular composition and transformation of dissolved organic matters (DOM). CaO 2 /O 3 (60/40 mg/gTS (total solid)) treatment showed more powerful sludge solubilization of 57.8% and cell death proportion of 46.1% over single CaO 2 or O 3 treatment. Hydrophilic extracellular polymeric substances, especially protein-like substances, were substantially degraded, and their conformation turned to be more hydrophobic, and carbohydrate-like, aminosugars-like, and lignins-like substances increased in CaO 2 /O 3 process. Meanwhile, CaO 2 /O 3 handling resulted in more decomposition of CHO-containing compounds than N-containing or S-containing compounds. Subsequently, 60 mg/gTS PFS (polyferric sulfate) reflocculation exerted a strengthened role in eliminating proteins & lipids-like, lignins-like, and unsaturated hydrocarbons-like substances, and especially S-containing compounds, which compensated for the unsatisfactory removal effects of these substances in the CaO 2 /O 3 oxidation process. Therefore, the CaO 2 /O 3 -PFS treated sludge with less hydrated DOM easily harvested deep-dewatering in pressure filtration. Furthermore, it was noteworthy that the presence of CaO 2 created an alkaline environment and served as the source of sustained-release H 2 O 2 , which accelerated O 3 decomposition and greatly improved • OH generation. These findings provided molecular insight into a novel sludge conditioning approach for ideal dewaterability based on the CaO 2 -enhanced peroxone process in sludge treatment.
研究领域:
环境工程
·
污水处理
·
化学工程
✓ 已验证
DOI
高影响因子
CHEMOSPHERE
·
2020
·
IF 5.778
Chang Bian,Dongdong Ge,Guanjun Wang,Yanting Dong,Wei Li,Nanwen Zhu,Haiping Yuan
The study proposed the ultrasound-activated persulfate oxidation as a novel approach to enhance sludge dewaterability. The results demonstrated that the reduction of water content of dewatered sludge cake was 16.5% and the capillary suction time was reduced to 39.5 s at the optimal conditions of 1.0 mmol/g-TS S 2 O 8 2- and ultrasound energy density of 2.0 kW L −1 within 15 min. The promotion of dewaterability was closely associated with the enlarged floc size, decreased viscosity, and near-neutral zeta potential . Meanwhile, the correlation analysis revealed that the protein in extracellular polymeric substances (EPS) governed sludge dewaterability, especially in loosely bound EPS. Three-dimensional excitation-emission matrix fluorescence spectroscopy , Fourier transform infrared spectroscopy and scanning electronic microscopy analysis revealed that ultrasound-activated persulfate oxidation treatment effectively degraded the gel-like EPS matrix and attacked cells, releasing the moisture which was trapped in EPS and cells. The aggregation of particles promoted the elimination of moisture. Furthermore, heavy metals in conditioned dewatered sludge cakes all satisfied the A level of agricultural land (GB4284-2018) requirements and the chemical speciation distribution of some heavy metals changed significantly.
研究领域:
环境科学
·
污水处理
✓ 已验证
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）