生活污泥用于去除硫化氢的驯化实验

本实验以城市污水处理厂污泥为原料,通过投加营养液和Na2S进行污泥驯化,培养出富含S2-降解菌的活性污泥,实验结果表明,通过两周连续投加Na2S的驯化,反应器内微生物已经达到稳态,活性污泥较为成熟,沉降比约为46%,SVI约为7 mL/g,MLSS约为6.6 g/L,S2-的去除率达到90%。     

Iron salts dosage for sulfide control in sewers induces chemical phosphorus removal during wastewater treatment

Chemical phosphorus (P) removal during aerobic wastewater treatment induced by iron salt addition in sewer systems for sulfide control is investigated. Aerobic batch tests with activated sludge fed with wastewater containing iron sulfide precipitates showed that iron sulfide was rapidly reoxidised in aerobic conditions, resulting in phosphate precipitation. The amount of P removed was proportional to the amount of iron salts added, and for the sludge used, ratios of 0.44 and 0.37 mgP/mgFe were obtained for ferric and ferrous dosages, respectively. The hydraulic retention time (HRT) of iron sulfide in sewers was found to have a crucial impact on the settling of iron sulfide precipitates during primary settling, with a shorter HRT resulting in a higher concentration of iron sulfide in the primary effluent and thus enabling higher P removal. A mathematical model was developed to describe iron sulfide oxidation in aerated activated sludge and the subsequent iron phosphate precipitation. The model was used to optimise FeCl₃ dosing in a real wastewater collection and treatment system. Simulation studies revealed that, by moving FeCl₃ dosing from the WWTP, which is the current practice, to a sewer location upstream of the plant, both sulfide control and phosphate removal could be achieved with the current ferric salt consumption. This work highlights the importance of integrated management of sewer networks and wastewater treatment plants.     

Post‐treatment of up‐flow anaerobic sludge blanket reactor effluents in activated sludge process‐based system for anionic surfactants

This paper presents the performance of two full‐scale up‐flow anaerobic sludge blanket–activated sludge process (UASB‐ASP)‐based sewage treatment plants (STPs) (surface and diffused aeration‐based activated sludge processes as post‐treatment units). Performance of this combination is compared with UASB–polishing ponds and UASB–ozonation‐based STPs. Post‐treatment units removed 89 and 92% of anionic surfactants (AS) by surface and diffused aeration, respectively. Finally, 0.61 and 0.23 mg/L of AS were discharged from post‐treatment steps after overall reduction of 90–92%. Final concentrations from UASB‐ASP‐based STPs were low compared with UASB–polishing ponds (3.60–4.91 mg/L) and UASB–ozonation (1.52 and 0.53 mg/L). Overall, UASB‐ASP‐based STPs were working efficiently for the removal of organics in terms of chemical oxygen demand (COD) (84%) and biochemical oxygen demand (BOD) (93%), but they need further modifications for the removal of AS up to the level of risk quotient [risk quotient (RQ)] ≤ 1 for no risk to aquatic environment.     

Methane formation in sewer systems

Methane formation and emission in sewer systems has not received as much attention as hydrogen sulphide formation. Through field measurements from two rising mains, with an average sewage temperature of 28.4 and 26.6 degrees C, respectively, at the time of sampling, this study shows that a significant amount of methane can be produced in sewer systems, and that this production is positively correlated with the hydraulic retention time of wastewater in these systems. The experimental results from a laboratory-scale sewer system fed with real sewage with a temperature of approximately 21 degrees C confirmed these field observations and further revealed that methanogenesis and sulphate reduction occur simultaneously in sewers, with methane production contributing considerably more to the loss of soluble COD in sewers than sulphate reduction. The production of methane in sewers at levels revealed by this study is a serious environmental concern as it potentially results in greenhouse emissions that is comparable to that caused by the energy consumption for the treatment of the same wastewater. Further, methane production in sewers influences sulphide production and its management due to the competition between methanogens and sulphate-reducing bacteria for potentially the same electron donors. The potential interactions between sulphate-reducing and methanogenic bacteria in sewer networks are discussed.     

Control of sulfide in sewer systems by dosage of iron salts: comparison between theoretical and experimental results, and practical implications

Removal of sulfide species from municipal sewage conveyance systems by dosage of iron salts is a relatively common practice. However, the reactions that occur between dissolved iron and sulfide species in municipal sewage media have not yet been fully quantified, and practical application relies heavily on empirical experience, which is often site specific. The aim of this work was to combine theoretical considerations and empirical observations to enable a more reliable prediction of the sulfide removal efficiency for a given dosing strategy. Two main questions were addressed, regarding the dominant sulfur species that results from the oxidation of sulfide by Fe(III) and the dominant precipitation reaction between Fe(II) and sulfide species. Comparison of thermodynamic prediction obtained by an equilibrium chemistry-based computer program (MINEQL+) with experimental results obtained by dosing ferrous salts showed that the product of precipitation is FeS under all operational conditions tested. Regarding the reaction between ferric salts and sulfide species, analysis of thermodynamic data suggested that the dominant product of sulfide oxidation under typical pe/pH conditions prevailing in municipal raw wastewater is SO(4)(2-). However, comparison between sulfide removal in laboratory experiments conducted with multiple samples of raw municipal sewage with a varying composition, and the prediction of MINEQL+ showed the main sulfide oxidation product to be S(0). In order to reduce sulfide in sewage to <0.1 mgS/l a minimal molar ratio of around 1.3 Fe to 1 S should be applied when ferrous salts are used, as compared with a minimal ratio of 0.9 Fe to 1 S required when ferric salts or a mixture of ferrous and ferric salts (at a 2 Fe(III) to 1 Fe(II) ratio) are used. It appears that the high Fe to S(-II) ratios often recommended in practice can be reduced considerably by applying tight in-line control.     

Inhibition of sulfate-reducing and methanogenic activities of anaerobic sewer biofilms by ferric iron dosing

Ferric iron is commonly used for sulfide precipitation in sewers, thus achieving corrosion and odour control. Its impact on the activities of sulfate-reducing bacteria and methanogens in anaerobic sewer biofilms is investigated in this study. Two lab-scale rising main sewer systems fed with real sewage were operated for 8 months. One received Fe³⁺ dosage (experimental system) and the other was used as a control. In addition to precipitating sulfide from bulk water, Fe³⁺ dosage was found to significantly inhibit sulfate reduction and methane production by sewer biofilms. The experimental reactor discharged an effluent containing a higher concentration of sulfate and a lower concentration of methane in comparison with the reference reactor. Batch experiments showed that the addition of ferric ions reduced the sulfate reduction and methane production rates of the sewer biofilms by 60% and 80%, respectively. The batch experiments further showed that Fe³⁺ dosage changed the final products of sulfate reduction with sulfide accounting for only 54% of the sulfate reduced. The other products could not be confirmed, but were not dissolved inorganic sulfur species such as sulfite or thiosulfate. The results suggest the addition of Fe³⁺ at upstream locations would minimize the ferric salts required for achieving the same level of sulfide removal. Fe³⁺ dosing could also substantially reduce the formation of methane, a potent greenhouse gas, in sewers.     

Fate and removal of selected endocrine‐disrupting compounds in sewage using activated sludge treatment

The variation and fate of four endocrine‐disrupting compounds (EDCs) composed of 4‐n‐nonylphenol (4‐n‐NP), bisphenol A (BPA), 17β‐estradiol (E2) and 17α‐ethinylestradiol (EE2) were investigated along treatment units in a sewage treatment plant (STP), China with anaerobic, anoxic and aerobic activated sludge processes. The mean concentrations were 64.8 ng/L (E2), 115.3 ng/L (4‐n‐NP), 171.5 ng/L (EE2), and 920.7 ng/L (BPA) in the influents, and 22.8 ng/L (E2), 50.9 ng/L (4‐n‐NP), 49.9 ng/L (EE2), and 84.3 ng/L (BPA) in the effluents. The biological treatment was more effective in removing NP, BPA and E2 from the aqueous phase than the primary treatment, while the latter could effectively remove EE2. Their possible removal mechanisms during the biological treatment with activated sludge were further explored through spiked batch experiments under three oxygen‐supplying conditions (anaerobic, anoxic and aerobic). The batch experiments showed that 4‐n‐NP, E2 and BPA were removed from the aqueous phase through biodegradation. The combination of sludge sorption and biodegradation accounted for the removal of EE2. Anoxic activated sludge showed the most rapid degradation of 4‐n‐NP, while E2 could be removed most effectively by aerobic activated sludge, and sludge sorption had a remarkable effect on its removal within the initial 15 min of the experiments under three oxygen‐supplying conditions.     

The balance of heavy metals through a sewage treatment works I. Lead,cadmium and copper

Concentrations of lead, cadmium and copper have been determined in the sewage sludges, sewages and effluent of a sewage treatment works. Treatment at this works is by primary sedimentation prior to biological treatment in a diffused air activated sludge plant. By analysis of composite samples corresponding to a 24-h input of raw sewage to the works, a mass balance of metals through the works has been estimated. The partition of the metals from raw sewage into the settled sewage and primary sludge, and from the settled sewage into the activated sludge and final effluent has been quantified.     

Nitrification via microorganism‐immobilized media using polyvinyl alcohol (PVA)

This study was conducted to investigate the nitrification of wastewater using polyvinyl alcohol (PVA) media immobilized with nitrifying bacteria. The microorganism‐immobilized media used in this study was prepared by mixing 10% (v/v) PVA, 6% (v/v) polyethylene glycol (PEG) and nitrifying microorganism culture solution. Analysis revealed that the nitrification rate when using the microorganism‐immobilized media increased to 49.1, 80.0 and 83.9% as the filling rate increased to 5, 15 and 25%, respectively. The mass transfer rate of the prepared microorganism‐immobilized media was estimated to be 37.69 mg/L·h maximum. The respiration rate was measured in order to compare with the microorganism‐immobilized media and the conventional biological treatment process of anaerobic‐anoxic‐oxic (A₂O). Respiration time of sludge and the media were similar, but the respiration rate of the microorganism‐immobilized media (initial 20.8 mg O₂/(L·h)) was higher than that of the activated sludge (initial 12.4 mg O₂/(L·h)).     

The balance of heavy metals through a sewage treatment works II. Chromium,nickel and zinc

Concentrations of chromium, nickel and zinc have been determined in the sewage sludges, sewages and effluent of a sewage-treatment works. Treatment at this works is by primary sedimentation prior to biological treatment in a diffused air activated sludge plant. By analysis of composite samples corresponding to a 24-h input of raw sewage to the works, a mass balance of these metals through the works has been estimated. The partition of these metals from raw sewage into settled sewage and primary sludge, and from the settled sewage into the activated sludge and final effluent has been quantified.     

Effects of sewage sludge on pH and plant availability of metals in oxidising sulphide mine tailings

A field study was conducted adjacent to the tailings deposit of the Aitik copper mine in the north of Sweden to investigate the effects of sewage sludge on pH and plant availability of Al, Mn, Cu, Zn, Ni, Pb, As, Cr and Cd in the oxidising sulphide tailings. One treatment was supplied with sewage sludge, while the control received NPK-fertiliser. The tailings samples were collected at the beginning and the end of the growing season and extracted by NH(4)NO(3), NH(4)Ac-EDTA and HNO(3). Plant tissue concentrations of the elements were determined in the above-ground parts of barley (Hordeum vulgare) and red fescue (Festuca rubra). The application of sewage sludge resulted in higher crop yields compared to the control, although the buffering capacity and the metal immobilising effect of the sludge were limited. The pH decreased from 6.6 to 4.3 in the control and from 6.4 to 4.8 in the sludge-treated tailings during the growing season, probably due to sulphide oxidation in the tailings. This resulted in increased levels of soluble elements in all treatments studied. Application of sewage sludge resulted in elevated levels of soluble Zn and lower values of soluble As and Cd in the unaltered tailings but increased levels of specifically adsorbed Cu, Ni and As in the oxidised tailings. This was partly reflected in the plants, as the application of sewage sludge resulted in 67 mg Zn kg(-1) in barley grains and 60 mg Zn kg(-1) in red fescue shoots, both values twice as high as the corresponding values in the control, but lower As contents in both straw (0.3 mg kg(-1)) and grain (0.06 mg kg(-1)) of barley compared to the control (0.6 and 0.2 mg kg(-1), respectively). In addition, red fescue grown in sludge-treated plots contained significantly higher levels of Al, Cu, Pb, As and Cr compared to the control. The levels of several metals in barley and red fescue grown in both treatments exceeded background values found in the literature. The Cu content in barley straw exceeded 100 mg kg(-1) in both treatments and might be toxic to grazing animals. Thus, this study suggests that adding sewage sludge to the mine tailings at Aitik would not counteract the effects of the sulphide oxidation in the tailings. Furthermore, using a sequential extraction technique proved preferable to using total metal analysis in order to predict plant uptake of the elements in the tailings.     

Co-conditioning and dewatering of chemical sludge and waste activated sludge

The conditioning and dewatering behaviors of chemical and waste activated sludges from a tannery were studied. Capillary suction time (CST), specific resistance to filtration (SRF), and bound water content were used to evaluate the sludge dewatering behaviors. Zeta potentials were also measured. Experiments were conducted on each sludge conditioned and dewatered separately, and on the sludge mixed at various ratios. Results indicate that the chemical sludge was relatively difficult to be dewatered, even in the presence of polyelectrolyte. When the waste activated sludge was mixed with the chemical sludge at ratios of 1:1 and 2:1, respectively, the dewaterability of chemical sludge improved remarkably while the relatively better dewaterability of the waste activated sludge deteriorated only to a limited extent. As the mixing ratios became 4:1 and 8:1, the dewaterability of the mixed sludge was equal to that of the waste activated sludge. The optimal polyelectrolyte dosage for the mixed sludge was equal to or less than that of the waste activated sludge. It is proposed that the chemical sludges act as skeleton builders that reduce the compressibility of the mixed sludge whose dewaterability is enhanced. Bound water contents of sludge decreased at low polyelectrolyte dosage and were not significantly affected as polyelectrolyte dosage increased. Advantages and disadvantages of co-conditioning and dewatering chemical sludge and waste activated sludge were discussed.     

Integrated Monitoring and Modelling of Odours in Sewerage Systems

The parameters of sewage that affect the production and resulting concentration of hydrogen sulphide in both liquid and gas phases have been monitored in a sewerage system. The data have been used to develop a model of the chemical and physical processes leading to sulphide production in sewers, so that the sources and causes of the problem can be identified. This model has been adapted to predict the concentrations of hydrogen sulphide that can be expected in the sewage and sewer atmosphere, following the construction of a major interceptor tunnel.     

SBR法工艺分析

运用反应动力学和系统工程理论，从生化反应推动力、基建投资及污水中原有微生物的充分利用等方面，对ＳＢＲ（序列间歇式反应器法）工艺与完全混合式及普通活性污泥工艺进行了分析比较，认为ＳＢＲ法可用于城市污水和有机工业废水处理。     

基于固体废弃物的高性能陶粒的研究

本文以宁波市污水处理厂废弃污泥、电厂粉煤灰和甬江淤泥等固体废弃物为原料,通过对原料基本性能、原料配合比和烧制参数的研究,烧制出高强低吸水率的高性能陶粒,为固体废弃物的资源化利用提供新的技术,具有较好的经济和社会效益。     

Sewage sludge conditioning by Fe(II)‐activated persulphate oxidation combined with skeleton builders for enhancing dewaterability

In this study, a joint application of Fe(II)‐activated persulphate oxidation and skeleton builders is used to condition sewage sludge for subsequent dewatering. The study mainly focuses on their efficacies and the optimization of the major operational parameters. The experimental results show that the joint application for conditioning sewage sludge is effective, especially using lime and ordinary Portland cement (OPC) as skeleton builders. Additionally, it is revealed that Fe(II)‐activated persulphate oxidation needs sufficient reaction time (20 min) to degrade organics in the sludge. The optimal conditions of this process are at Fe²⁺ = 47.6 mg g^?1 (dry solids), S₂ = 119.1 mg g^?1, lime = 446.4 mg g^?1, and OPC = 297.6 mg g^?1, under which the water content of dewatered sludge cake is 54.8% and the specific resistance to filtration (SRF) is 4.3 × 10¹¹ m kg^?1 with a reduction efficiency of 96.6%.     

An examination of the surface characteristics of activated sludge in relation to bulking during the treatment of paper mill wastewater

The addition of mineral talc, Aquatal^®(Toulouse, France), to activated sludge treating paper mill effluents and its effect on settlement characteristics has been investigated. One laboratory study and a full‐scale investigation on a large waste water treatment plant (WWTP) with a capacity of 500.000 population equivalent (p.e.) have been carried out using this mineral. The sludge in the full‐scale plant was filamentous and had specific sludge volume index (SSVI) values in excess of 250. The talc dosing which was adapted to sludge settleability reduced SSVI values by 38%, improved the total suspended solids' concentrations by 86% and reduced the specific sludge load by 34%. In the laboratory‐scale plant, the sludge had SSVI values of 200–260 before treatment and was hydrophilic. The use of Aquatal^® at a dose of 0.7 g/g mixed liquor suspended solids (MLSS) took 2 weeks to reduce the SSVI to 78. It also increased the hydrophobicity to a balanced 50%. The use of mineral converted the somewhat diffuse flocs into a compact structure.     

Optimization of intermittent, simultaneous dosage of nitrite and hydrochloric acid to control sulfide and methane productions in sewers

Free nitrous acid (FNA) was previously demonstrated to be biocidal to anaerobic sewer biofilms. The intermittent dosing of FNA as a measure for controlling sulfide and methane productions in sewers is investigated. The impact of three key operational parameters namely the dosing concentration, dosing duration and dosing interval on the suppression and subsequent recovery of sulfide and methane production was examined experimentally using lab-scale sewer reactors. FNA as low as 0.26 mg-N/L was able to suppress sulfide production after an exposure of 12 h. In comparison, 0.09 mg-N/L of FNA with 6-h exposure was adequate to restrain methanogenesis effectively. The recovery of sulfide production was well described by an exponential recovery equation. Model-based analysis revealed that 12-h dosage at an FNA concentration of 0.26 mg-N/L every 5 days can reduce the average sulfide production by >80%. Economic analysis showed that intermittent FNA dosage is potentially a cost-effective strategy for sulfide and methane control in sewers.     

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in sewage treatment plants

In this study, the concentrations of PFOS and PFOA in the biological units of various full-scale municipal sewage treatment plants were measured. Samples of influent, primary effluent, aeration tank effluent, final effluent and grab samples of primary, activated, secondary and anaerobically digested sludge were collected by 5 sampling events over one year. The two sewage treatment plants (STPs) selected for this study include plant A receiving 95% domestic wastewater and plant B receiving 60% industrial wastewater and 40% domestic wastewater. PFOS and PFOA were observed at higher concentration in aqueous and sludge samples in plant B than that of plant A. Mass flow of PFOS increased significantly (mean 94.6%) in conventional activated sludge process (CAS) of plant B, while it remained consistent after the secondary treatment in plant A. Mass flow of PFOA increased 41.6% (mean) in CAS of plants A and B and 76.6% in membrane biological reactor (MBR), while it remained unchanged after the treatment of liquid treatment module (LTM). Our results suggest that mass flow of these two compounds remains consistent after treatment of activated sludge process operating at short sludge retention time (SRT). Seasonal variations of PFOS in concentrations of raw sewage were found in plant A, while PFOA did not have significant seasonal variation in both plants A and B.     

Socio‐economic impacts of the pharmaceuticals detection and activated carbon treatment technology in water management – an example from the Czech Republic

The fast development of laboratory methods has revealed increased amounts of trace concentrations of pharmaceuticals and personal care products (PPCP) in waste waters in the Czech Republic. This paper focuses on the expected costs to solve this problem by quaternary treatment of waste water based on activated carbon filtration. The one‐time investment costs in 155 wastewater treatment plants (WWTPs) with a capacity of over 10 000 population equivalent (PE) would represent an amount of around 300 million EUR. The increase in end‐user operating costs would be 0.4 EUR/m³, which would mean a 15% increase in water and sewage costs. A sociological survey showed that most respondents (65%) would agree with an increase in price but only by 10%. Currently the cost of the quaternary treatment of wastewater is based primarily on estimates. Therefore changes in legislation leading to stricter limits and an increase in the efficiency of wastewater treatment should be preceded by additional applied research.