Recovery Of Sludge Research Articles

Exploring the pyrolysis process of simulated oily sludge: Kinetics, mechanism, product distribution, and S/N elements migration

Pyrolysis is an important method for energy recovery and harmless treatment of oily sludge, definite reaction mechanism and the transformation of S and N elements is a key to improve the pyrolysis products. In this paper, a simulated oil sludge (SOS) was pyrolyzed at various temperatures of 400–700 °C in a tube furnace focusing on pyrolysis process, kinetic parameters, reaction mechanisms, S and N element migration patterns and product distributions. Kinetic parameters were deducted by FWO, KAS, Friedman and Starink methods, and the activation energy were 186.23–231.20 kJ/mol (Avg. 210.71 kJ/mol), 190.18–233.80 kJ/mol (Avg. 212.02 kJ/mol), 196.93–242.01 kJ/mol (Avg. 209.88 kJ/mol) and 184.82–230.95 kJ/mol (Avg. 218.67 kJ/mol), respectively, showed high similarity. All the pre-exponential factors were higher than 109 s−1, which indicated high reactivity of SOS during pyrolysis, and the pyrolysis process followed the nucleation growth model (A3). Pyrolysis temperatures had a significant influence on products distribution. The maximum yields of pyrolysis tar and gas were observed at 550 °C and 700 °C, respectively. Pyrolysis tar was dominated by aromatics and acids, while pyrolysis gas was mainly composed of H2 and CH4. Additionally, high temperatures could facilitate the transfer of more S and N into tar or gas products, and S and N compounds were mainly thiophene-S, sulfoxide-S, pyridine-N and pyrrole-N in char and CS2, CH3SH, COS, SO2, H2S, NH3, HCN and NOx in gas.

Formate-facilitated recovery of wastewater anammox granular sludge from oxygen inhibition: Effects and mechanisms

Oxygen leakage due to poor reactor sealing or accidental aeration can have detrimental impacts on the performance of wastewater anammox processes. Strategies of restoring functionality of anammox consortia are scarce, and providing appropriate chemical reducing reagents may help reduce oxidative damage. This study characterized the responses of anammox granular sludge (AnGS) to oxygen inhibition, and identified formate as an effective promoter capable of facilitating activity recovery, while other organics (acetate, glucose, methanol) were less effective. Upon 12 h of air exposure (DO: 1.2 ± 0.1 mg/L), the total nitrogen removal efficiency of a lab-scale AnGS reactor decreased from 85.15 % to 45.46 %. Compared with natural recovery (without chemical addition), potassium formate at 10 mg COD/L for 3 days significantly increased the total nitrogen removal efficiency, both in the short-term (66.68 % vs 57.09 %, 3 days post inhibition) and long-term (82.34 % vs 72.88 %, 30 days post inhibition). By examining sludge morphology, metagenome and transcriptome, the following potential mechanisms were proposed: 1) rapidly decreasing intracellular ROS; 2) enhancing nitrite turnover; 3) maintaining granular sludge integrity; 4) facilitating interspecies metabolic interactions. The ability of formate to facilitate sludge recovery from oxygen inhibition also implies its potential in mitigating other oxidative stresses in wastewater anammox reactors.

Investigating potential auxiliary anaerobic digestion activity of phage under polyvinyl chloride microplastic stress

Polyvinyl chloride (PVC) microplastics present in sewage were trapped in sludge, thereby hindering anaerobic digestion performance of waste active sludge (WAS). Phages regulate virocell metabolism by encoding auxiliary metabolic genes (AMGs) related to energy acquisition and material degradation, supporting hosts survive in harsh environments and play a crucial role in biogeochemical cycles. This study investigated the potential effects of phages on the recovery of WAS anaerobic digestion under PVC stress. We observed a significant alteration in the phage community induced by PVC microplastics. Phages encoded AMGs related to anaerobic digestion and cell growth probably alleviate PVC microplastics inhibition on WAS anaerobic digestion, and 54.2 % of hydrolysis-related GHs and 40.8 % of acidification-related AMGs were actively transcribed in the PVC-exposed group. Additionally, the degradation of chitin and peptidoglycan during hydrolysis and the conversion of glucose to pyruvate during acidification were more susceptible to phages. Prediction of phage-host relationship indicated that the phyla Pseudomonadota were predominantly targeted hosts by hydrolysis-related and acidification-related phages, and PVC toxicity had minimal impact on phage-host interaction. Our findings highlight the importance of phages in anaerobic digestion and provide a novel strategy for using phages in the functional recovery of microplastic-exposed sludge.

Resource recovery of water treatment plant sludge and river sediment as phosphorus removal material: feasibility and mechanisms

ABSTRACT Excessive phosphorus is a critical contributor to eutrophication, necessitating the use of substantial amounts of phosphorus removal materials. To address the challenge of managing water treatment plant sludge and river sediment while also supplying mass-produced phosphorus-removing materials for projects targeting phosphorus removal in water bodies, this paper attempted to study the feasibility of preparing phosphorus removal materials by mixing and calcining water treatment plant sludge and river sediment (C-WTPS/RS). The study examined the transformation of phosphorus forms in C-WTPS/RS before and after adsorption. Furthermore, X-ray fluorescence spectrometer, zeta potential, scanning electron microscope, Brunauer–Emmett–Teller equation, Barrett–Joyner–Halenda model, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were employed to elucidate the phosphorus removal mechanisms. The results showed that C-WTPS/RS was effective in removing phosphorus from water and preventing the release of phosphorus from the sediment. Additionally, C-WTPS/RS had a low risk of releasing phosphorus and metals within the pH range of natural water bodies. These proved that it is feasible to remove phosphorus by C-WTPS/RS. After adsorption, the increased phosphorus in C-WTPS/RS was mainly dominated by the non-apatite inorganic phosphorus within inorganic phosphorus. The main phosphorus removal mechanisms of C-WTPS/RS were physical adsorption, electrostatic adsorption, chemical precipitation, and ligand exchange.

Hierarchical Approach to the Management of Drinking Water Sludge Generated from Alum-Based Treatment Processes

The management of drinking water treatment plant (DWTP) sludge is challenging for water treatment facilities. Previous studies reported mainly on handling sludge through landfilling, release into water bodies, discharge into wastewater treatment plants, onsite disposal, and incineration methods for the treatment of sludge. The limitations of these sludge-handling methods are well documented. This article focuses on the hierarchical approach as an alternative and comprehensive method for handling DWTP sludge. The core of hierarchical management streamlines the minimization of the generated DWTP sludge; treatment of DWTP sludge to reduce toxicity; changing of the physicochemical form of DWTP sludge; and finally, the reuse, recycling, and recovery of DWTP sludge. The premise is to achieve zero landfilling of DWTP sludge, establish a circular economy, generate job opportunities, and preserve the environment. Thus, this study also proposes two main technologies, which are gravity-based sludge separators for fractionating the sludge and photocatalytic membrane reactors (PMRs) as a technology for the treating and/or recovery of nutrients and minerals from DWTP sludge. Until the chemical deductive or minus approach becomes a reality in water treatment, the use of PMRs and gravity-based sludge separators will enhance the management of DWTP sludge when incorporated into the hierarchical approach.

Sludge Recovery from Wastewater Treatment Plants: A Review of Current Practices and Tips

Sludge recovery from “wastewater treatment plants” (WWTP) is an important aspect of the wastewater treatment process as it allows for the reuse of valuable resources and the reduction of waste. In this review, we examine current practices and tips for sludge recovery from wastewater treatment plants. We first discuss the various types of sludge produced in the treatment process, including primary, secondary, and tertiary sludge, and their respective characteristics. We then review the different methods used for sludge recovery, including thickening, dewatering, drying, and their respective advantages/disadvantages, and provide tips for optimizing sludge recovery, including proper sludge management, optimization of treatment processes, and incorporation of energy-efficient technologies. In parallel, we present an overview of the production, operation and nutrient composition of these sludges. Overall, the aim of this study is to provide an overview of sludge recovery in wastewater treatment plants and to offer practical insights for improving the efficiency and sustainability of this important process as well as the valorization of this important raw material.

Research on Resource Recovery and Disposal of Copper-Containing Sludge.

Copper-containing sludge is a common by-product of industrial activities, particularly electroplating and metal processing. This type of sludge contains high concentrations of heavy metals such as copper, which can pose a potential threat to the environment. Therefore, its treatment and disposal require special attention. Due to its efficient mass and heat transfer characteristics, the suspended state technology has shown significant potential for application in a number of key processes, including the drying, decomposition, and reduction of copper-containing sludge. This paper presents an in-depth analysis of the current status of the application of the suspended state technology in the treatment of copper-containing sludge. Based on this analysis, a device for the treatment of copper-containing sludge in the suspended state was designed, through which the characteristics of copper-containing sludge in the oxidative decomposition and reduction phases are investigated. The research objects were gas concentration, temperature, contact state, and particle size time. Orthogonal experiments were initially employed to investigate the relationship between the influencing factors and the conversion rate of copper oxides. This was followed by a single-factor influence study, which led to the determination of the optimal process parameters for the decomposition experiments of the Cu-containing sludge in an oxidizing atmosphere. The 100 μm Cu-containing sludge was reacted with 10% O2 gas at a flow rate of 1 m/s for 3 min under the condition of 900 °C. The process parameters were then determined as follows: The research objects were gas concentration, temperature, contact state, and particle size time. Orthogonal experiments were employed to investigate the relationship between the influencing factors and the copper conversion rate. This was followed by a single-factor influence study, which determined the optimal process parameters for the copper-containing sludge reduction experiments. The 200 μm copper-containing sludge was reacted for 5 min at a flow rate of 7% carbon monoxide at a flow rate of 1.5 m/s under the condition of 800 °C.

An Overview of the Thermochemical Valorization of Sewage Sludge: Principles and Current Challenges

With the increase in the world population and economic activity, the production of sewage sludge has grown, and its management has become an environmental problem. The most traditional method of managing sewage sludge is to dispose of it in landfills and on farmland. One way to valorize sewage sludge is to use thermochemical conversion processes to produce added-value products such as biochar, biofuels, and renewable gases. However, due to the high moisture content, thermochemical conversion using processes such as pyrolysis and traditional gasification involves multiple pre-treatment processes such as material drying. Hydrothermal thermochemical processes usually require high pressures, which pose many challenges to their application on a large scale. In this work, the advantages and disadvantages of the different existing thermochemical processes for the recovery of sewage sludge were analyzed, as well as the resulting industrial and environmental challenges. A SWOT analysis was carried out to assess the different thermochemical processes in terms of technical feasibility, economic viability, and broader market considerations.

IMPROVEMENT OF AQUACULTURE WASTEWATER CO-DIGESTION PERFORMANCE BY CATTLE DUNG USING A THERMOPHILIC PILOT REACTOR AND FERTILISER RECOVERY

The fundamental challenge to balancing the fuel demand is the risk of process instability. Research on energy recovery from aquaculture effluent addresses energy demands and environmental pollution concerns. The current study examined the effectiveness of anaerobic co-digestion of aquaculture effluent in a 45 L thermophilic reactor without utilising chemical catalysts. The partially digested cow manure created a substantial buffering capacity in this co-digestion process that balanced the volatile fatty acids (VFA). The methane produced was 0.45 m3 CH4/kg VS, whereas 71% of the chemical oxygen demand (COD) was removed. Thermophilic wet co-digestion was used to shorten the digestion and co-digestion phases. The results showed the highest methane was produced after 5 days (0.085 m3 CH4/(kgVSday), and 81% of total methane potential was attained after 9 days. The system proficiency for eliminating volatile solids was more than 36% after 6 days. Sludge recovery was 0.08 m3 sludge/m3 wastewater and water recovery was 0.85 (m3 sludge/m3 wastewater). It is suggested that wet co-digestion at a thermophilic state was favourable for the commercial application of co-digestion of aquaculture wastewater.

A Mini Review on Sewage Sludge and Red Mud Recycling for Thermal Energy Storage

Sewage sludge and red mud, as common industrial waste, have become a research hotspot in the field of achieving carbon peaking and carbon neutrality, reducing carbon emissions, and solving environmental problems. However, their treatment and disposal have always been a difficult problem in the environmental field. Utilizing these two materials for thermal energy storage can not only improve energy utilization efficiency but also further reduce carbon emissions during their treatment process, providing a new approach for sustainable development in the industrial sector. This article summarizes the research progress for the resource recovery of sewage sludge and red mud for direct thermal energy recovery and composite phase change energy storage. After proper treatment, sludge and red mud can be directly used as energy storage materials. In addition, sludge and red mud can be combined with phase change materials to prepare composite materials with an excellent energy storage performance. This composite has broad application prospects in fields such as solar energy utilization and building energy efficiency. However, there are still some challenges and issues in this resource recovery and utilization, such as potential environmental pollution during the treatment process, the long-term stability of energy storage materials, and cost-effectiveness, which require further research and resolution. The purpose of this paper is to evaluate the potential of sewage sludge and red mud as energy storage materials, to explore their feasibility and advantages in practical applications, and to reveal the research progress, technical challenges, and future development directions of these two materials in the field of thermal energy storage.

A new strategy for accelerating recovery of anaerobic granular sludge after low-temperature shock: In situ regulation of quorum sensing microorganisms embedded in polyvinyl alcohol sodium alginate

Low-temperature could inhibit the performance of anaerobic granular sludge (AnGS). Quorum sensing (QS), as a communication mode between microorganisms, can effectively regulate AnGS. In this study, a kind of embedded particles (PVA/SA@Serratia) based on signal molecule secreting bacteria was prepared by microbial immobilization technology based on polyvinyl alcohol and sodium alginate to accelerate the recovery of AnGS system after low temperature. Low-temperature shock experiment verified the positive effect of PVA/SA@Serratia on restoring the COD removal rate and methanogenesis capacity of AnGS. Further analysis by metagenomics analysis showed that PVA/SA@Serratia stimulated higher QS activity and promoted the secretion of extracellular polymeric substance (EPS) in AnGS. The rapid construction of EPS protective layer effectively accelerated the establishment of a robust microbial community structure. PVA/SA@Serratia also enhanced multiple methanogenic pathways, including direct interspecies electron transfer. In conclusion, this study demonstrated that PVA/SA@Serratia could effectively strengthen AnGS after low-temperature shock.

Research on oil recovery of oily sludge by subcritical/supercritical hydrothermal upgrading

AbstractBACKGROUNDSub/supercritical hydrothermal treatment is a promising technology for efficient resource utilization and complete harmlessness of oily sludge, which is significant for promoting the green and sustainable development of the petroleum industry. In this paper, the effects of reaction temperature, reaction pressure, reaction time and oil content on oil recovery and oil quality (composition, desulfurization and denitrification, and heavy metal content) are studied in detail.RESULTSIt was found that the temperature was the most critical parameter, and the optimal process conditions were 350°C, 20 MPa, 60 min and 12 wt% oil content, under which the oil recovery rate could reach 70.46%. The content of N and S in the recovered oil could be as low as 0.87 and 0.536 wt%, and the ratio of H/C was higher than 1.6.CONCLUSIONIt was found that reaction temperature had the most significant effect on oil recovery compared with other reaction parameters. Heavy metals are transferred from the oil phase to the water and solid phases, so the content of heavy metals in the oil phase is up to standard. The experiment shows that supercritical water heat treatment of oily sludge is feasible, which makes possible the commercial application of sub/supercritical water thermal oil collection technology. © 2024 Society of Chemical Industry (SCI).

Valorization of fat balls and primary scum from wastewater treatment: a promising renewable lipid feedstock for biodiesel production.

We investigated the potential of waste materials from wastewater treatment plants (WWTPs) to serve as an alternative lipid feedstock for biodiesel production. The average lipid recoveries from fat balls (46.4%) and primary scum (49.5-54.5%) were higher than the lipid recovery of primary sludge (15.8-16.4%). The yield of biodiesel produced from the extracted lipids ranged from 5.7 to 20.1%. There were considerable site- and season-dependent variations in the characteristics of the lipid waste materials. Radiocarbon analysis indicated the presence of fossil-derived carbon (26.0-42.0%) in the biodiesel obtained from wastewater lipids. Finally, we estimated the potential for biodiesel production from WWTP-derived lipids; about 333.0 metric tons of biodiesel per year could be produced from fat balls and primary scum in Japan. The results indicate that lipid-rich materials from WWTPs represent a valuable alternative feedstock for biodiesel production.

Evaluating the environmental and economic performance of biological and advanced biological wastewater treatment plants by life cycle assessment and life cycle costing.

The primary objective of this study is to assess and establish benchmarks for environmental and economic sustainability of biological and advanced biological wastewater treatment plants (WWTPs) with different treatment technologies and characteristics. Furthermore, the study aims to determine the beneficial role of WWTPs to reduction of eutrophication potential. Environmental and economic sustainability of ten municipal WWTPs was assessed using life cycle assessment (LCA) and life cycle costing (LCC). In the first section of the study, LCA was performed to determine the environmental performance of the WWTPs. Furthermore, net environmental benefit (NEB) approach was implemented to reveal the beneficial role of WWTPs to eutrophication potential. In the subsequent section, LCA-based LCC was conducted by integrating the results of LCA. The most significant environmental impact was determined as marine aquatic ecotoxicity, which is highly affected from the generation and transmission of electricity consumed in the WWTPs. Wastewater recovery and co-incineration of sewage sludge in cement kiln ensure significant environmental savings on ozone layer depletion, human toxicity, acidification, photochemical oxidation, and abiotic depletion (fossil fuel) potential. Considering NEB approach, the highest NEB values were found for the WWTPs with the higher organic load and nutrient concentration in the influent. The results of LCC in WWTPs varied between 0.21 and 0.53 €/m3. External (environmental) costs were evaluated higher than internal (operational) costs for all selected WWTPs. While eutrophication was the highest among environmental costs, electricity cost was the highest among operational costs for almost all WWTPs.

Assessment of occupational external radiation exposure of workers in the Southwest of Libya using portable NaI detector

In this study, gamma dose rates generated from the naturally occurring radioactive materials (NORM) were measured in the waste streams of a large scale and sludge onshore petroleum operations. Measurements conducted in this work involved: sludge recovery from separation tanks, sludge forming, NORM storage, scaling in oil tubulars, scaling in gas production and sedimentation in produced water evaporation ponds. Field work was carried out in many places of different terrain of an operation oil exploration and production in Murzuq basin in the Southwest of Libya. The radiation dose rates were measured using portable InSpector-1000. A total of 400 dose rates were acquired. The highest dose rate was 70 μSv/h acquired in sludge stored in barrels. The estimated mean annual equivalent doses in this field were in the range of 0.2–2.8 mSv/y in the first scenario, while in the second scenario the calculated mean annual equivalent doses were in the range of 0.04–0.68 mSv/y. It is assumed that workers may face various exposures in the field where measurements took place, considering the total annual effective dose to be 1.53 mSv/y. The main radioisotopes detected in these samples indicated by the display of the measuring device were 226Ra and 228Ra but detecting both radioisotopes in the same run is not achievable by using the display of the screen.

The second messenger (cyclic diguanylate and autoinducer-2) promotes N-acylated-homoserine lactones-based quorum sensing for enhanced recovery of stored aerobic granular sludge

Efficient quorum sensing (QS) response is the premise for recovering the activities of stored aerobic granular sludge (AGS). This study aims to explore the crosstalk between the secondary messenger and the N-acylated-homoserine lactones (AHLs) to yield protein-rich granules efficiently from stored AGS by enhancing its QS efficiency selectively. 80 nmol/L cyclic diguanylate (c-di-GMP) with 20 nmol/L AHLs could increase the activity of isocitrate lyase activity (ICD) by 89 % and isocitrate dehydrogenase activity (ICDHc) by 113.5 %, to accelerate the tricarboxylic acid (TCA) cycle for yielding excess proteins by 166.4 %. In contrast, 80 nmol/L autoinducer-2 (AI-2) with 20 nmol/L AHLs could increase the activities of ICD and ICDHc by 485 % and 54.5 %, respectively, accelerating the glyoxylate (GCA) cycle to activate fat acid synthesis for stimulating polysaccharides (PS) secretion by 137.9 %. The strategy with c-di-GMP successfully recovers the refrigerated-stored and dried-stored AGS into proteins-rich AGS, with enriched functional strains for the PN secretion.

Bifunctional hybrid magnetic colloidal clusters for efficient oil sludge recovery

Oil contamination of water bodies due to oil spills, industrial waste discharge, oil leaks, etc. poses a major threat to the quality of groundwater, soil, and living organisms. To combat this issue through effective environmental remediation, efficient and cost-effective materials and innovative strategies are required. Here, we report a novel bifunctional magnetic material for efficient oil sludge removal using superparamagnetic colloidal nanocrystal clusters(BSPM-CNC) of nickel ion doped iron oxide with a shell of nitrogen-activated carboxymethyl cellulose char. The BSPM-CNC is synthesized by using a single-step procedure using water as a solvent. The crystallite and cluster size were tuned by varying Ni2+ ion concentration, carboxymethyl cellulose, and urea ratio. The cluster size was found to increase, when the carboxymethyl cellulose and urea ratio was reduced, due to insufficient stabilization of the capping agent that allowed the formation of secondary structures. X-ray photoelectron spectroscopy results confirmed the presence of nitrogen in the shell because of the condensation of OH and carbonyl groups of CMC with amine groups of urea, sp2-type carbon, C-O/N and O-CO bonding states. Laser Raman spectra of the char showed two major bands G and D bands, originating from the sp2 bonds and sp2 microdomains of the bond angle disorder caused by the sp3 hybridizations, respectively. The BSPM-CNC was found to be very efficient for oil sludge removal, where an oil removal efficiency of ∼ 98% was achieved with a cluster loading of 16 mg/L. The mechanism of sorption of oil are π-π interaction between aromatic hydrocarbons and graphitic domains of BSPM-CNC, Lewis-acid base interaction between nitrogenous char and delocalized electron cloud, and absorption into the pores of clusters. Our new approach provides a new platform to produce magnetic nanoclusters for the efficient removal of oil pollutants.

A review of carbon recovery in sewage treatment and analysis of product options for a typical water recycling plant

Carbon recovery and sustainable management of sewage sludge from wastewater treatment plants were reviewed regarding the technical and market supply potentials, environmental, economic, and social benefits, and technology readiness. The...

A reduction in global impacts through a waste-wastewater-energy nexus: A life cycle assessment

This work presents the results of a comparison of three different management scenarios (one current and two future) of waste, wastewater, and their related energy systems in Southern European regions. A Life Cycle Assessment (LCA) has been applied to all the different steps of the complex scenarios in order to provide a more holistic, robust, and scientific approach that is able to highlight the beneficial effects of the integration of different plants (Waste to Energy - WtE, Anaerobic digestion - AD, wastewater treatment plant - WWTP) included in a symbiotic nexus. The LCA results have shown that an important reduction in the impact of Municipal Solid Waste (MSW) management is obtained from the recovery of separately collected materials, but there is still a large gap that could be filled by the introduction of energy recovery (by means of AD and WtE) and through its symbiotic use to support the anaerobic digestion, wastewater reuse, and sludge recovery processes. The proposed approach, which is based on a waste-wastewater-energy nexus and industrial symbiosis, could be adopted to support these regions to significantly increase circularity and fill the gap, thus favoring a significant rapprochement in the path toward the New Green Deal promoted by the European Union.

Simultaneous chelated heavy metals removal and sludge recovery through titanium coagulation: From waste to resource

Green methods for chelated heavy metals treatment and recovery are essential for coordinated development of resources and environment. Herein, a simple and competent method, titanium salt (TiCl4) coagulation was developed to remove and recycle chelated heavy metals. Our results revealed that this method proved to be effective for metals-citrate [Cu(II), Ni(II), Zn(II) and Cr(VI)], achieving removal efficiencies of 95 %, 92 %, 99 %, and 99 % within 30 min, surpassing direct alkaline precipitation and well-used Fe(III) coagulation. Whereafter, the copper-containing sludge was successfully transformed into copper-doped titanium dioxide (TiO2) photocatalysts by facile calcination. Through comprehensively investigating physicochemical properties by a suite of characterization techniques, we confirmed that doping of Cu induced bandgap narrowing, high specific surface area as well as the formation of oxygen vacancy. Accordingly, the recycling photocatalysts showed remarkable enhanced photocatalytic performance than the pristine TiO2, achieving improvement in the degradation efficiency of 82 %, 61 % and 67 % for carbamazepine(CBZ), bisphenol A (BPA) and methyl orange (MO). In addition, both radical (OH and O2−) and non-radical (1O2 and h+) pathways synergistically contributed to the removal of organic pollutants during photocatalysis. Ultimately, based on economic feasibility assessment and life cycle assessment (LCA), the copper-containing titanium coagulation sludge reuse for photocatalyst could bring lower carbon emissions, reduced environmental risks and higher economic benefits. The elucidation of this study provides new insights into the removal and recycle of chelated heavy metals from wastewater by using an environment-friendly and cost-effective method.