Removal of sulfate and heavy metals by sulfate reducing bacteria in short-term bench scale upflow anaerobic packed bed reactor runs

Mildly acidic metal (Cu, Zn, Ni, Fe, Al and Mg), arsenic and sulfate contaminated waters were treated, over a 14 day period at 25 degrees C, in a bench-scale upflow anaerobic packed bed reactor filled with silica sand and employing a mixed population of sulfate-reducing bacteria (SRB). The activity of SRB increased the water pH from approximately 4.5 to 7.0, and enhanced the removal of sulfate and metals in comparison to controls not inoculated with SRB. Addition of organic substrate and sulfate at loading rates of 7.43 and 3.71 kg d(-1) m(-3), respectively, resulted in >82% reduction in sulfate concentration. The reactor removed more than 97.5% of the initial concentrations of Cu, Zn and Ni, while only >77.5% and >82% of As and Fe were removed, respectively. In contrast, Mg and Al levels remained unchanged during the whole treatment process. The removal patterns for Cu, Zn, Ni and Fe reflected the trend in their solubility for their respective metal sulfides, while As removal appeared to coincide with decreasing Cu, Zn, Ni and Fe concentrations, which suggests adsorption or concomitant precipitation with the other metal sulfides.     

Effect of sulfate on anaerobic reduction of nitrobenzene with acetate or propionate as an electron donor

Sulfate is frequently found in wastewaters that contain nitrobenzene. To reveal the effect of sulfate on the reductive transformation of nitrobenzene to aniline - with acetate or propionate as potential electron donors in anaerobic systems - an acetate series (R1-R5) and a propionate series (R6-R10) were set up. Each of these was comprised of five laboratory-scale sequence batch reactors. The two series were amended with the same amount of nitrobenzene and electron donor electron equivalents, whereas with increasing sulfate concentrations. Results indicated that the presence of sulfate could depress nitrobenzene reduction. Such depression is linked to the inhibition of nitroreductase activity and/or the shift of electron flow. In the acetate series, although sulfate did not strongly compete with nitrobenzene for electron donors, noncompetitive inhibition of specific nitrobenzene reduction rates by sulfate was observed, with an inhibition constant of 0.40 mM. Propionate, which can produce intermediate H₂ as preferred reducing equivalent, is a more effective primary electron donor for nitrobenzene reduction as compared to acetate. In the propionate series, sulfate was found to be a preferential electron acceptor as compared to nitrobenzene, resulting in a quick depletion of propionate and then a likely termination of H₂-releasing under higher sulfate concentrations (R9 and R10). In such a situation, nitrobenzene reduction slowed down, occurring two-stage zero-order kinetics.     

Effect of acid speciation on solid waste liquefaction in an anaerobic acid digester

Laboratory scale experiments were carried out to evaluate and determine the suitable working conditions for the enhancement of volatile fatty acids (VFAs) production with the stabilization of solid pineapple waste (peel) simultaneously when operating two-phase anaerobic digestion. It was found that acid production, enhanced when the digester was operated at neutral pH. VFAs, could be obtained at about 50 g/kg-waste within 14 days when operating at pH 6.5-7.5 compared to 33 g/kg-waste for digester operated at pH 5.0-6.0 for 32 days. The total volatile solid reduction of 42-48% was obtained with a 51-57% volume reduction at neutral pH. The effect of undissociated acids on the activity of acetogenic bacteria was also studied. The inhibitory level of undissociated acids for acidogenesis was found to be about 2300, 650, and 120 mg/L at pH 5, 6, and 7, respectively. The results revealed that at low pH, undissociated acids are inhibitory. It was found that for efficient operation of two-phase anaerobic digestion, both VFAs concentration and pH should be controlled.     

Combined use of calcium salts and polymeric aluminium hydroxide for defluoridation of waste waters

The combined use of calcium salt and polymeric aluminium hydroxide, P, for treatment of fluoridated waste water has been described. In the proposed method of treatment the calcium ions acts as the precipitant and polymeric aluminium hydroxide as the coagulant. At low fluoride concentrations (2 × 10⁻³ M) the precipitation reaction of calcium fluoride is a slow process. The residual fluoride concentrations found experimentally approached the theoretically predicted values only at high calcium concentrations (| F | _t/ | Ca | _I molar ratio = 0.24) and for long equilibration times. The addition of calcium fluoride seeds (approx. 20 mg 1⁻¹) accelerated the precipitation process and the results obtained for the residual fluoride concentrations were close to the theoretically calculated ones regardless of the calcium ion concentration used. Under these conditions fine CaF₂ precipitate with poor settleability was formed. The addition of small amounts of polymeric aluminium hydroxide, P, (F/Al molar ratio = 10) greatly facilitates the settleability of the precipitate. The advantage of using P over alum for the removal of fluoride is that less concentration of the former is required and the reproducibility of the results are good. The effect of sulphate on the precipitation of calcium fluoride has been also studied. Tests with fluoride containing waste water collected from aluminium industry showed that fluoride can be effectively removed.     

接触氧化法在屠宰废水处理中的应用

结合具体实例,详细介绍了采用接触氧化法处理屠宰废水的设计,包括工艺流程,各单体处理单元工艺及经营管理等方面的相关内容,经本系统处理,出水水质均达到《肉类加工工业污染物排放标准》及回用水执行《生活杂用水水质标准》中的一级标准。     

某矿综合污水处理可行性分析

全面阐述了西山煤矿总公司某矿污水治理的现状和存在的问题 ,分析了煤矿水污染的特点及其处理方法和存在的问题 ,提出了改进方案 ,通过现场了解和模型实验得出了可行性结论     

含酚废水的生物处理方法及其进展

介绍了含酚废水的主要来源和危害,对常见含酚废水的生物处理方法的原理和特点进行了介绍,并阐述了这些方法近年来的研究进展,为开展含酚废水的污染防治研究工作提供了理论指导。     

Fate of LCFA in the co-digestion of cow manure, food waste and discontinuous addition of oil

Different concentrations of oily waste were added in a discontinuous mode and recurrently to anaerobic continuous stirred tank reactors fed with cow manure and food waste. Four continuous stirred tank reactors were run in parallel. A control reactor (R1) received no additional oil and R2, R3 and R4 received increasing concentrations of oil in two different experimental approaches. First, the lipids composition was forced to change suddenly, in three moments, without changing the total chemical oxygen demand (COD) fed to the reactors. The only long chain fatty acid (LCFA) detected onto the R1 solid matrix was palmitic acid (C16:0). Nevertheless in the solid matrix of R2, R3 and R4 C16:0 and stearic acid were detected. For occasional increase in the oil concentration up to 7.7 gCOD_oil/L_reactor (55% Oil_COD/Total_COD) no statistical differences were detected between the reactors, in terms of methane production, effluent soluble COD, effluent volatile fatty acids and total and volatile solids removal. Therefore this experiment allowed to conclude that cow manure–food waste co-digestion presents sufficient buffer capacity to endure solid-associated LCFA concentration up to 20–25 gCOD-LCFA/kgTS.In a second experiment higher concentrations of oil were added, raising occasionally the concentration in the reactors to 9, 12, 15 and 18 gCOD_oil/L_reactor. All pulses had a positive effect in methane production, with the exception of the highest oil pulse concentration, that persistently impaired the reactor performance. This experiment demonstrates that threshold values for LCFA and C16:0 accumulation onto the solid matrix, of about 180–220 gCOD-LCFA/kgTS and 120–150 gCOD-C16:0/kgTS, should not be surpassed in order to prevent persistent reactor failure, as occurs in some full scale co-digestion plants.     

竖向流曝气生物滤池工艺在污水处理中的应用

详细论述了以竖向流曝气生物滤池为核心工艺建设的重庆市铜梁县旧县镇污水处理厂的工艺流程及主体构筑物的功能和设计参数,重点介绍了竖向流曝气生物滤池的调试及运行效果,并提出了具体建议。     

西曲矿井下污水处理改造

全面阐述了西曲矿井下污水治理的现状和存在问题,分析了矿井污水污染的特点和BH净水工艺的处理效果通过深入现场和现场实验,得出了可行性结论,提出了改进方案,对其它煤矿矿井污水处理具有深远的意义。     

浅谈污水处理中氧化沟工艺的研究发展

在阐述了氧化沟工艺特点的基础上，对其发展进行了综述，同时指出随着对该工艺的研究和开发，它必将成为一种很有竞争力的污水处理工艺，拥有良好的发展前景。     

Selective recovery of nickel over iron from a nickel-iron solution using microbial sulfate reduction in a gas-lift bioreactor

Process streams with high concentrations of metals and sulfate are characteristic for the mining and metallurgical industries. This study aims to selectively recover nickel from a nickel-iron-containing solution at pH 5.0 using a single stage bioreactor that simultaneously combines low pH sulfate reduction and metal-sulfide formation. The results show that nickel was selectively precipitated in the bioreactor at pH 5.0 and the precipitates consisted of ≥83% of the nickel content. The nickel-iron precipitates were partly crystalline and had a metal/sulfur ratio of 1, suggesting these precipitates were NiS and FeS. Experiments focusing on nickel recovery at pH 5.0 and 5.5 reached a recovery of >99.9%, resulting in a nickel effluent concentration <0.05 μM. The mixed microbial population included known sulfate reducers and acetogens. This study shows that selective metal precipitation in a single stage sulfate reducing bioreactor operated at low pH has the potential to produce metal-sulfides that can be used by the metallurgical industry as a resource for metal production.     

硫酸盐还原菌在硫酸盐废水处理中的应用

介绍了硫酸盐废水来源、硫酸盐还原菌（SRB）的分类、生理特性及代谢方式,阐述了SRB处理硫酸盐废水的机理,概括了国内外利用SRB处理重金属废水、高浓度硫酸盐有机废水的应用现状,对SRB处理硫酸盐废水的技术前景进行了展望。     

传统污水处理厂节能降耗的措施

以宁波市江东北区污水处理厂为例,根据该厂的工艺和设备特点,从生产电耗、药耗、中水回用等角度出发,在追求出水水质达标排放前提下,探讨了传统污水处理厂节能降耗的措施,以实现降低处理成本的目的。     

泥水平衡盾构系统中废弃泥浆的减量化处理

通过对沉降剂种类、投加量、搅拌时间、搅拌速度的研究,针对不同种类的废弃泥浆确定了不同的减量化工艺,通过该工艺处理之后得出:粘土质废弃泥浆1含水率从81%降至64%,体积缩小为处理前的53%;砂质废弃泥浆2含水率从63.9%降至51.8%,体积缩小为处理前的75%;废弃砂质泥浆3含水率从89.4%降至67.9%,体积缩小为处理前的33%。     

Energetic valorization of wood waste: estimation of the reduction in CO2 emissions

This paper investigates the potential CO₂ emission reductions related to a partial switch from fossil fuel-based heat and electricity generation to renewable wood waste-based systems in Flanders. The results show that valorization in large-scale CHP (combined heat and power) systems and co-firing in coal plants have the largest CO₂ reduction per TJ wood waste. However, at current co-firing rates of 10%, the CO₂ reduction per GWh of electricity that can be achieved by co-firing in coal plants is five times lower than the CO₂ reduction per GWh of large-scale CHP. Moreover, analysis of the effect of government support for co-firing of wood waste in coal-fired power plants on the marginal costs of electricity generation plants reveals that the effect of the European Emission Trading Scheme (EU ETS) is effectively counterbalanced. This is due to the fact that biomass integrated gasification combined cycles (BIGCC) are not yet commercially available. An increase of the fraction of coal-based electricity in the total electricity generation from 8 to 10% at the expense of the fraction of gas-based electricity due to the government support for co-firing wood waste, would compensate entirely for the CO₂ reduction by substitution of coal by wood waste. This clearly illustrates the possibility of a ‘rebound’ effect on the CO₂ reduction due to government support for co-combustion of wood waste in an electricity generation system with large installed capacity of coal- and gas-based power plants, such as the Belgian one.     

浅谈目前建筑垃圾处理中存在的问题与对策

分析了我国当前对建筑垃圾的处理现状,阐述了建筑垃圾对城市环境的影响,系统总结了我国当前在建筑垃圾处理中存在的问题,并针对建筑垃圾利用中存在的问题,对建筑垃圾减量化、开发利用、资源化等途径提出了一些可行的措施。     

Correlation of bacterial communities supported by different organic materials with sulfate reduction in metal-rich landfill leachate

Several different organic materials, typical of those used in passive treatment systems for mine influenced water, were tested for their ability to support sulfate-reducing bacteria and sulfate reduction in an anaerobic biological reactor (ABR). The quantity of sulfate-reducing bacteria (SRB) in each organic material, as determined using quantitative polymerase chain reaction (q-PCR) of the dissimilatory sulfite reductase (dsr) gene, correlated with the initial C/N ratio of each material. Potential sulfate reduction rates measured in the laboratory ranked silage > compost = molasses/hay > cattails > pulp mill biosolids and correlated with the q-PCR estimates of SRB in the submerged materials. A comparison of bacterial communities using 16S rRNA gene clone library sequencing revealed similar distribution of clones among the phyla Bacteroidetes, Firmicutes and Proteobacteria for silage, compost and molasses/hay after 174 days of exposure in the seepage water. Silage, the most successful material tested, contained more δ-Proteobacteria-related sequences than the other materials and Spirochaetes-related clones were more abundant in silage than in compost or molasses/hay. According to sequenced dsr clones, the SRB community in silage differed from that for compost and molasses/hay, with fewer Desulfovibrio- and more Desulfomicrobium-related sequences in the silage. Pulp mill biosolids used in the ABR since 2004 contained an overall bacterial community that was more diverse than those for the freshly submerged organics, but only Desulfovibrio desulfuricans-related sequences were found in the dsr library.     

Hydrolysis and acidification of waste activated sludge at different pHs

The effect of pH from 4.0 to 11.0 on the hydrolysis and acidification of waste activated sludge (WAS) was investigated. Experimental results showed that at room temperature the sludge hydrolysis was in the following order: alkaline>acidic>(neutral and blank test), and between pH 6.0 and 11.0 the sludge hydrolysis increased with pH. The three main components, soluble protein, carbohydrate and volatile fatty acids (VFAs) in the hydrolytic product were analyzed. It was observed that both the soluble protein and carbohydrate increased with pH in the pH range 7.0-11.0, but also increased to a smaller extent with pH from 7.0 to 4.0. The VFAs concentration was also affected by pH. Under alkaline conditions, the VFAs production was significantly higher than under other conditions. The concentration of VFAs on the 8th day of fermentation at pH 4.0, 7.0 and 10.0 was, respectively, 354.49, 842.00 and 2708.02 mg/L, while VFAs in the blank test was only 633.59 mg/L. The VFAs consisted of acetic, propionic, iso-butyric, n-butyric, iso-valeric and n-valeric acids, but acetic, propionic and iso-valeric were the three main products. Also, the release of soluble phosphorus and ammonia and the production of methane was studied during WAS fermentation at different pHs.     

垃圾土中有机物降解引起的体积缩减量与时间的关系研究

基于自制的侧限压缩–降解仪,对不同降解条件进行模拟对比试验,系统地研究了不同降解条件下垃圾土中有机物的生物降解过程。试验中收集了生物反应气和渗滤液并测定了相关指标,观测了垃圾试样的竖向变形,利用生物反应器成功地模拟了填埋场生物反应的三个反应阶段:初始调整阶段、过渡阶段及产酸阶段。通过对比试验的方法直接得到了生物降解引起的体积缩减量,研究表明,生物降解引起的体积缩减量随时间的延长呈指数型增长,生物降解引起的体积缩减量占垃圾体积的24%左右,降解速率及体积缩减量随反应阶段的不同而有较大的差异,产酸阶段生物降解引起的体积缩减量占总的生物降解引起体积缩减量的70%左右。