Neutralization Sludge Research Articles

MODELLING THE CONDITIONS OF CIRCULATING WATER SUPPLY FOR A COPPER ORE PROCESSING PLANT

There is carried out a quantitative assessment of the changes in the circulating water composition under the influence of its conditioning method in a circulating water supply system of the Balkhash Concentrator Plant. Research objects are circulating water model mixtures which are reuse in copper ores flotation after clarification in a tailings dam. They are obtained in a laboratory because of modelling the mixing and storage conditions of enrichment tailings from the Balkhash Concentrator Plant and acid effluents neutralization sludge from the Balkhash Copper Smelter Plant with industrial effluents from other enterprises in Balkhash region. There is considers two schemes for conditioning of recycle water in the process water supply system: by mixing clarified water obtained during the combined or separate waste storage (enrichment tailings and acid effluents neutralization sludge). Studies haveshown that after mixing these flows in the tail collector and their combined storage in the tailings dam chemical and physico-chemical processes occur that contribute to the removal of several pollutants (copper, arsenic, iron, zinc, cadmium, and nickel) from circulating water, which can be explained by the binding of cations these elements into insoluble compounds. Based on the results obtained, it is recommended to use a combined waste storage technology for the circulating water conditioning.

Significant in situ sludge yield reduction in an acidic activated sludge system

Minimizing sludge generation in activated sludge systems is critical to reducing the operational cost of wastewater treatment plants (WWTPs), particularly for small plants where bioenergy is not recovered. This study introduces a novel acidic activated sludge technology for in situ sludge yield reduction, leveraging acid-tolerant ammonia-oxidizing bacteria (Candidatus Nitrosoglobus). The observed sludge yield (Yobs) was calculated based on the cumulative sludge generation and COD removal during 400 d long-term operation. The acidic process achieved a low Yobs of 0.106 ± 0.004 gMLSS/gCOD at pH 4.6 to 4.8 and in situ free nitrous acid (FNA) of 1 to 3 mg/L, reducing sludge production by 58 % compared to the conventional neutral-pH system (Yobs of 0.250 ± 0.003 gMLSS/gCOD). The acidic system also maintained effective sludge settling and organic matter removal over long-term operation. Mechanism studies revealed that the acidic sludge displayed higher endogenous respiration, sludge hydrolysis rates, and higher soluble microbial products and loosely-bounded extracellular polymer substances, compared to the neutral sludge. It also selectively enriched several hydrolytic genera (e.g., Chryseobacterium, Acidovorax, and Ottowia). Those results indicate that the acidic pH and in situ FNA enhanced sludge disintegration, hydrolysis, and cryptic growth. Besides, a lower intracellular ATP content was observed for acidic sludge than neutral sludge, suggesting potential decoupling of catabolism and anabolism in the acidic sludge. These findings collectively demonstrate that the acidic activated sludge technology could significantly reduce sludge yield, contributing to more cost- and space-effective wastewater management.

Geochemical Evaluation of Manganese Neutralization Sludge for Mn-Containing Mine Drainage Treatment

Conventional neutralization treatment for manganese (Mn)-bearing mine drainage provides a challenge of cost-efficiency, and new approaches should be explored for efficient removal of Mn. We focused on Mn neutralization sludge, a by-product of the Mn-bearing drainage treatment process, which was assumed to be useful as a water purification material. Mn and zinc (Zn) removal tests in simulated drainage were performed using Mn neutralization sludge, and the reaction mechanism was elucidated using geochemical modeling and X-ray absorption fine structure (XAFS) analysis. The results showed that the addition of sludge enabled to lower the Mn and Zn concentration below Japanese effluent standard (10 mg dm−3 for Mn; 2 mg dm−3 for Zn) within 1 h. Furthermore, heavy metal immobilization was achieved at neutral pH (7–8) with the sludge addition, while the conventional neutralization process without adding the sludge requires higher pH (>10) to lower Mn concentration. These removal behaviors were not explainable by considering only well-known phenomena: hydroxide precipitation, surface complexation reaction onto δ-MnO2, and autocatalytic Mn oxidation. Hence, we advanced the geochemical model for simulation, suggesting that a surface complexation reaction onto γ-MnOOH greatly contributed to the removal of Mn. Besides, Zn was calculated to be predominantly precipitated as ZnMn2O4. Solid residue analysis by XAFS measurement supported the result of above calculation, validating the reliability of the constructed geochemical model. Overall, we concluded that the advanced geochemical model would be useful in predicting the Mn and Zn behavior during mine drainage treatment with Mn neutralization sludge.Graphical abstract

Recovery hydrotalcite from neutralization sludge of acid mine drainage with high manganese for degradation of norfloxacin with activated peroxymonosulfate

Acid mine drainage is rich in metals (including transition metals), so the neutralization treatment based on AMD for in situ regulation will ultimately result in sludge with potential catalytic effects. In this study, we reported a catalyst (MC-LDHs) that differed from traditional catalysts in that it was derived from AMD neutralized sludge containing high concentrations of Mn, which was a typical industrial waste. The catalytic performance of activated PMS for the removal of norfloxacin (NOR, a typical antibiotic) was evaluated under different operating conditions. The contribution of active species in the reaction system was evaluated through quenching experiments, and the types of free radicals were further determined through electron spin resonance experiments. In addition, density functional theory was used to simulate the electron transfer and vulnerable sites of NOR in the adsorption of PMS by MC-LDHs. Subsequently, the degradation pathway of NOR was inferred based on DFT results, and the toxicity changes of intermediate products were predicted. This study has reduced the cost of catalysts and simplified the preparation process of doped catalysts, thus providing a new strategy for catalyst preparation, which is of great significance for the promotion and application of advanced oxidation process.

REHABILITATION OF MAN-MADE FORMATION OF ABANDONED COPPER PYRITE DEPOSITS ON THE EXAMPLE OF LEVIKHINSKY MINE (MIDDLE URALS)

Link for citation: Rybnikova L.S., Rybnikov P.A., Navolokina V.Y. Rehabilitation of man-made formation of abandoned copper pyrite deposits on the example of Levikhinsky mine (Middle Urals). Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 137-150. In Rus. The relevance of the research is related to the need to rehabilitate of abandoned copper pyrite deposits affected by acid mine waters and justify measures to clean up the existing clarification pond. The main aim is to study the sludge composition and justify the measures to reduce the environmental load on the hydrosphere. Objects: clarification pond and neutralization sludge of the Levikhinsky copper pyrite mine acid mine waters. Methods. Laboratory studies of water and bottom sediments were carried out using atomic emission and mass spectral analysis; methods of flame emission spectrometry, flame atomic absorption, photometric method with Nessler's reagent, titrimetric, mercumetric and potentiometric methods; mass spectrometry with ionization in inductively coupled plasma and gravimetric method. Results. Sludge samples are dominated by sulfates (gypsum and bassanite), iron oxides and hydroxides (goethite), carbonates (calcite), clay minerals (mainly hydromica) and chlorine-containing salts (carnallite). The chemical composition of the sludge is dominated by oxides of iron, sulfur and calcium. The analysis of water and acid extracts showed that up to 24 elements belonging to hazard classes 2, 3 and 4 can be leached from the sludge in concentrations exceeding the maximum allowable values for fishery water bodies. Several options for the use of sludge from the clarification pond were analyzed: reclamation of waste rock dumps and substandard ores; backfilling of mined-out area of quarries; production of building materials; extraction of components; storage of sludge in geotubes (Geotube). The most rational is the disposal of sludge as the production of building materials on the basis of a public-private partnership, the implementation of which will allow the state and the private sector to derive mutual benefit.

Economic Analysis of Thermal–Catalytic Process of Palm Oil (Elaeis guineesensis, Jacq) and Soap Phase Residue from Neutralization Process of Palm Oil (Elaeis guineensis, Jacq)

Palm oil is, from an economic, environmental, and social point of view, a vegetable oil with great potential and the state of Pará-Brazil is Brazil’s great producer. In addition, soap phase residue or palm oil neutralization sludge (PONS), a byproduct of the neutralization step of the chemical refinement of palm oil, is produced, posing a huge problem for waste disposal and management in the production process of refined palm oil (RPO). In this context, this work aims to systematically investigate the economic analysis of the thermal–catalytic process of crude palm oil (CPO) and palm oil neutralization sludge (PONS). The thermocatalytic processes of CPO and PONS carried out at pilot scale and their economic feasibility were analyzed. The yields of biofuels produced by fractional distillation were also presented. The physicochemical properties of CPO and PONS, as well as those of organic liquid products obtained by the thermal–catalytic process of CPO and PONS were taken into account in the economic analysis. In addition, the chemical composition organic liquid products obtained by thermal–catalytic process of CPO and PONS, as well as its distillation fractions (green gasoline, green kerosene, green light diesel and heavy diesel), used as key factors/indicators on the economic analysis. The analysis of the key factors/indicators from the thermocatalytic processes of CPO and PONS showed economic viability for both crude palm oil (Elaeis guineensis, Jacq) and palm oil neutralization sludge. The minimum fuel selling price (MFSP) obtained in this work for the biofuels was 1.59 USD/L using crude palm oil (CPO) and 1.34 USD/L using palm oil neutralization sludge (PONS). The best breakeven point obtained was of 1.24 USD/L considering the PONS. The sensibility analysis demonstrated that the pyrolysis and distillation yields are the most important variables that affect the minimum fuel-selling price (MFSP) in both economic analyses.

Calcium peroxide and freezing co-pretreatment enhancing short-chain fatty acids production from waste activated sludge towards carbon–neutral sludge treatment

Short-chain fatty acids (SCFAs) recovery through anaerobic fermentation is a promising technology to achieve carbon–neutral in waste activated sludge (WAS) management. After 0.15 g CaO2/g volatile suspended solids (VSS) addition and three-cycle freezing co-pretreatments, the maximal SCFAs production of 438.5 mg COD/g VSS was achieved within 4 days fermentation, and more than 70 % of SCFAs was composed of acetate and propionate, which achieved a higher level than reported in previous studies. Mechanism explorations elucidated that co-pretreatment triggered sludge solubilization, promoting the release of biodegradable organics, providing more biodegradable substrates for SCFAs generation. Further microbial community analysis indicated that the abundances of hydrolytic microorganisms and acidogens were enriched, whereas methanogens were inhibited. Besides, environmental analysis suggested that co-pretreatment could achieve carbon reduction benefits of 0.116–0.291 ton CO2/ton WAS, demonstrating its huge carbon–neutral potential benefits.

Selective separation of calcium from zinc-rich neutralization sludge by sulfidation roasting and HCl leaching

Zinc-rich neutralization sludge is a hazardous waste which is from the process of zinc metallurgical industry. In this study, a combined process of sulfidation roasting and HCl leaching was developed to treat zinc-rich neutralization sludge. The effects of roasting parameters including carbon dosage, roasting temperature and time on sulfidation roasting were investigated by thermodynamic calculation and laboratory experiments. The optimal conditions have been established as: carbon powder dosage of 15%, temperature of 700 °C, and time of 60 min. Under the conditions, 95.48% of zinc contained in the residues was converted into sulfides and 98.36% of sulfur was fixed into the roasting product. Meanwhile, the calcium sulfate was converted into calcite and calcium sulfide. The roasted sample was then subjected to HCl leaching process for the separation of calcium and zinc. About 93.75% of calcium was extracted by the leaching under the optimal conditions: HCl concentration of 3 mol/L, liquid to solid ratio of 5 mL/g, leaching temperature of 25 °C, and leaching time of 10 min. After the HCl leaching, about 97.37% of zinc was concentrated into the leaching residue with zinc grade of 45.86%. XRD analysis indicated that the leaching residue mainly composed of sphalerite and wurtzite, which can be used as a raw material for zinc smelting.

Sorption of rare earth elements on schwertmannite and their mobility in acid mine drainage treatments

Rare Earth Elements (REE) are nowadays considered critical raw materials due to their increasing use in modern industry and their shortage of supply. Acid mine drainage (AMD) contains REE concentrations several orders of magnitude higher than the rest of continental and marine waters, and the sludge from its treatment may become a supplementary source of REE. Schwertmannite, a Fe(III)-sulfate-hydroxide is the most common mineral precipitated from AMD and a main constituent of the neutralization sludge. The objective of this work is to study the mechanism of REE retention in synthetic schwertmannite and to predict the REE behavior in a column experiment mimicking an AMD passive remediation system.Suspensions of synthetic schwertmannite in sulfate solutions show that Y and the lanthanides are effectively sorbed at pH values higher than 4.5, and sorption is complete at pH values higher than 6.5. The experimental partition coefficients clearly show a preferential enrichment of heavy REE in the solid phase. Unlike the rest of the REE, Sc sorption occurred at a lower pH, from 3 to 5. The experimental results have been described with a non-electrostatic surface complexation model in which the aqueous complex MSO4+ exchanges with two H+ from the surface of schwertmannite, forming a bidentate surface complex, (XO)2MSO4-. Scandium sorption was also accurately predicted with the addition of a second bidentate surface complex, (XO)2MOH.The equilibrium constants for REE sorption on schwertmannite calculated in the present work, together with those for REE sorption on basaluminite (Lozano et al., 2019, GCA, 258, 50–62) were used to model the behavior of different REE observed in the pore water and solid of a column experiment. Schwertmannite and basaluminite were the main solid phases formed due to the progression of the neutralization. First schwertmannite precipitated at pH below 4 and then basaluminite precipitated at pH above 4. Both minerals can sorb REE in a similar pH range. However, since Y and the lanthanides sorbed at pH values higher than 5, their sorption only occurred on basaluminite. In contrast, the Sc sorption edge extended from pH 3 to 5 and Sc partially sorbed on schwertmannite. As a practical consequence, REE preferentially accumulated in the basaluminite residue of AMD neutralization systems, but a minor fraction of Sc can be retained in the schwertmannite waste.

Production of Eco-refinery Pulp from Moso Bamboo Using Steam Treatment Followed by Milling Treatment

In this study, we produced cellulose nanofiber (CNF) from moso bamboo using high-temperature and high-pressure steam treatment combined with the milling treatment. This pretreatment method can be considered as an environmentally friendly method because the treated product contains only wood-derived components and water that generally do not lead to significant corrosion problems and formation of neutralization sludge. The specific tensile strengths of CNF obtained in this work were almost the same values as that of a commercial CNF. Furthermore, an eco-refinery pulp was made of holocellulose and CNF those were obtained from moso bamboo by this pretreatment method and its mechanical strength was evaluated. By changing the steam treatment conditions, it is possible to produce eco-refinery pulp of various specific tensile strengths adapted to the application and purpose.

Combined and individual applications of ozonation and microwave treatment for waste activated sludge solubilization and nutrient release

This study focused on the separate and combined applications of ozonation and microwave treatment to enhance the phosphorus and ammonia release from waste activated sludge. Twenty-six batch experiments were run with or without acidic (pH 2) and alkaline (pH 10) pretreatments and different ozone dosages. Also, microwave post-treatments were applied to enhance phosphorus release efficiency. Results showed that ozonation is an effective technology for solubilization and release without any pre or post-treatment, reactive phosphorus content increased from 1.9 to 3.6 mg PO4-P/g MLSSin (89.5% increase) with 19.4% COD release. Alkaline pretreatment enhanced sludge solubilization and phosphorus release at most (23.9% COD release and 152.6% PO4-P increase); however, decreases in ammonia, calcium and magnesium concentrations pointed out a loss of a part of released phosphorus, due to struvite or apatite precipitation. Acidic pretreatment reduced the sludge solubilization during ozonation (10% COD release) but prevented the uncontrolled precipitation and enhanced the phosphorus release (115.8% PO4-P increase). For microwave treatment, acid pretreated sludge showed higher release than alkaline pretreated or neutral sludge. Among different process combinations, acid pretreatment/ozonation/microwave experiments have shown the highest sludge solubilization and nutrient release (48% COD release and 579% PO4-P increase); however, the difference between acid pretreatment/microwave and acid pretreatment/ozonation/microwave was not significant in terms of phosphorus release (479% PO4-P increase, p = 0.082). Thus, pH 2/microwave may be a cost-effective and feasible alternative for nutrient recovery from waste sludge. For struvite precipitation, pH 8.5 were determined as optimum level. Also using fine struvite particles as seed increased struvite precipitation efficiency.

Durability Assessment of Cement Matrices for Neutralization Sludge Disposing

The paper deals with durability assessment of different cement matrices for disposing of hazardous waste – neutralization sludge from physical chemical processing from an active industrial source. The durability of the matrices is estimated on the basis of laboratory testing results of compressive strength and leachability tests those indicate the possibility of matrices to bind the hazardous substances inside matrices. These tests were performed on the matrices after different time period.

Co-treatment of flotation waste, neutralization sludge, and arsenic-containing gypsum sludge from copper smelting: solidification/stabilization of arsenic and heavy metals with minimal cement clinker.

Flotation waste of copper slag (FWCS), neutralization sludge (NS), and arsenic-containing gypsum sludge (GS), both of which are difficult to dispose of, are major solid wastes produced by the copper smelting. This study focused on the co-treatment of FWCS, NS, and GS for solidification/stabilization of arsenic and heavy metals with minimal cement clinker. Firstly, the preparation parameters of binder composed of FWCS, NS, and cement clinker were optimized to be FWCS dosage of 40%, NS dosage of 10%, cement clinker dosage of 50%, mill time of 1.5h, and water-to-binder ratio of 0.25. On these conditions, the unconfined compressive strength (UCS) of the binder reached 43.24MPa after hydration of 28days. Then, the binder was used to solidify/stabilize the As-containing GS. When the mass ratio of binder-to-GS was 5:5, the UCS of matrix can reach 11.06MPa after hydration of 28days, meeting the required UCS level of MU10 brick in China. Moreover, arsenic and other heavy metals in FWCS, NS, and GS were effectively solidified or stabilized. The heavy metal concentrations in leachate were much lower than those in the limits of China standard leaching test (CSLT). Therefore, the matrices were potential to be used as bricks in some constructions. XRD analysis shows that the main hydration products of the matrix were portlandite and calcium silicate hydrate. These hydration products may play a significant role in the stabilization/solidification of arsenic and heavy metals.

A Novel Application of Expanded Glass Materials in Sulfate Reducing Bacteria Cultivation

Smelting waste water is typically considered as an environmental pollutant. It will contaminate watercourses, crops and aquatic organism when it is discharged into the environment. Traditionally, the metallurgy plant treats this kind of waste water with neutralization method. However, the neutralization method usually ends up with large amounts of neutralization sludge which is a typical kind of hazardous solid waste. In our research, we used an up-flow anaerobic sludge bed to treat smelting waste water which was neutralized to a certain pH. We combined the traditional neutralization method with microbial technique. The neutralized water was pumped into the bioreactor that had been inoculated with sulfite reducing bacteria on a novel expanded hollow glass bead. In our research, we decreased the lime consume and sludge production, and we decrease the metal ion and sulfate in the smelting waste water at the same time. We combined the traditional neutralization method with microbial treatment and developed a novel solution to deal with smelting waste water. After 8 weeks, the concentration of Zn2+ was decreased by 34.7%, and the concentration of SO42- was decreased by 58.3%.

Separation and recovery of ZnS from sulfidized neutralization sludge via the hydration conversion of CaSO4 into bulk CaSO4·2H2O crystals

Hydrothermal sulfidation–flotation is considered to be a feasible means for the heavy metal recovery from neutralization sludge (NS) generated by the lime-neutralization process in our previous studies. However, the as-generated sulfides prefer to aggregate on the surface of CaSO4 during hydrothermal sulfidation, which causes difficulties in the sulfides recovery via flotation. In this study, the hydration of CaSO4 was proposed to promote the separation of sulfides (mainly ZnS) in sulfidized NS. When hydration was performed on pure CaSO4, the rod-shaped CaSO4 with an average length of 10 μm was converted into CaSO4·2H2O with an increased average length of 100–400 μm. Based on this, hydration was introduced into the sulfidized NS, and the CaSO4 in the sulfidized NS was converted into bulk CaSO4·2H2O crystals. Sieving experiments toward the hydration product show that a total of 90.66% of the Zn was concentrated in a −48 μm sieving product. To further improve the zinc grade of the −48 μm sieving product, a flotation test was conducted, during which a concentrate with Zn grade of 37.11% was obtained and Zn recovery reached 66.87%. In contrast, when flotation was directly performed on sulfidized NS, the Zn grade in concentrates and Zn recovery were only 21.96% and 37.43%, respectively. Therefore, the hydration of CaSO4 in sulfidized NS can effectively promote the separation and recovery of ZnS.

Behavior and effect of calcium during hydrothermal sulfidation and flotation of zinc-calcium-based neutralization sludge

Neutralization sludge (NS), a calcium-based heavy metal waste, was produced in large quantities during wastewater treatment using lime milk neutralization in the nonferrous metal industry. During hydrothermal sulfidation and flotation of NS, the phase transition of calcium compounds might play a crucial role in the subsequent flotation for low metal recovery. During hydrothermal sulfidation, calcium minerals in NS were converted and further developed into bulk CaSO4 crystals with many nano-ZnS crystals adhering on its surface. Specifically, the conversion of CaCO3 into CaSO4 could accelerate the sulfidation of NS. However, the presence of CaSO4 could slow the growth rate of ZnS crystals, which imposes a negative effect on subsequent flotation. CaSO4 crystals with irregular shapes and incomplete crystallization combined with nano-ZnS crystals were frequently observed in concentrates after flotation, whereas CaSO4 crystals of regular shape and high crystallinity were mainly discovered in tailings, indicating that modifying the crystalline nature and texture of CaSO4 crystals is a feasible method for separating ZnS and CaSO4 and for increasing metal recovery. Furthermore, the adsorption of collectors on CaSO4 was hardly detected, indicating that CaSO4 barely competed with ZnS for collectors during flotation.

Solidification of Hazardous Waste with the Aim of Material Utilization of Solidification Products

In order to reduce the amount of hazardous waste this work deals with the possibility of using solidification technology to transform the hazardous waste with the aim to achieve the material utilization of solidification products. For this purpose, it is necessary to determine a suitable solidification formula for solidification product made of the chosen hazardous waste – neutralization sludge. Particular solidification formula is chosen on the basis of advanced experimental examination of solidification products. Solidification products have to comply with the environmental requirements and physical and mechanical properties arising from their suitable further use in building industry or for land rehabilitation processes.

Sulfidation of heavy-metal-containing neutralization sludge using zinc leaching residue as the sulfur source for metal recovery and stabilization

Heavy-metal-containing neutralization sludge (NS) and sulfur-containing zinc leaching residue (ZLR), both of which are difficult to dispose of, are two of the main solid wastes produced in the Pb/Zn smelting process. This study focused on the application of ZLR as a sulfur source to sulfidize NS, which could then be separated by flotation for metal recovery. A mixture of NS, ZLR and additional sulfur was first mixed by ball milling, and then successively treated by hydrothermal sulfidation and flotation. Based on the chemical properties of NS and ZLR, the effects of the mass ratio of NS-to-ZLR, the amount of sulfur and ball milling time on sulfidation and the floatability and stability of the sulfidation product were investigated. The sulfidation percentages of Zn and Pb were as high as 82.6% and 95.6%, respectively. Flotation tests revealed that Zn and Pb can be enriched with a concentrate grade of 21.3% Zn and 3.4% Pb. Toxicity characteristic leaching procedure (TCLP) results indicated that stabilization of NS and ZLR occurred after sulfidation.

Verification of the Possibility of Solidification Product Made of Neutralization Sludge use in the Building Industry

This paper deals with hazardous waste solidification/stabilisation, specifically neutralization sludge that comes from active industrial sources and neutralization sludge that comes from old ecological sources. As solidification agents fluidized bed combustion ash, classic fly ash and ordinary Portland cement were used. According to the valid legislation and selected possible future use of solidification product a laboratory testing of proposed solidification/stabilisation recipes was performed. The results of leachability tests, unconfined compressive strength and ecotoxicological test showed that solidification product use as a technological and reclamation material on depots and setting pits is possible.

Study on Variation Trends of Heavy Metals Contents in Process of Sludge Energy Utilization

Application of sludge-to-energy is an important direction for disposal of sludge, and it is necessary to provide the contents change of heavy metals in sludge. Through sampling in situ and analysis in laboratory, distributions of seven heavy metals in five kinds of sludge, which were come from wastewater treatment plant of Jilin Petrochemical Company of Petro China, were studied, and contents change of heavy metals in the course of sludge-to-energy were analyzed. The results were compared with the other sludge in the factory and municipal wastewater treatment plants and the national standard. The results showed that the heavy metal contents are different in the different sludge, and the mean is Fe>Cu>Zn>Mn>Pb >Cr>Cd, the total content distributions from high to low is incinerated sludge, chemical sludge, activated sludge, neutralization sludge, digested sludge. Contents of Cu and Zn exceeded the the mean of 44 municipal wastewater treatment plants and GB18918-2002. After biogas of digested sludge and energy of incinerated sludge were recovered, heavy metal contents exceeded in varying degrees, which were paid more attention for treatment and utilization.