Co-treatment of acid mine drainage with municipal wastewater: performance evaluation

Co-treatment of acid mine drainage (AMD) with municipal wastewater (MWW) using the activated sludge process is a novel treatment technology offering potential savings over alternative systems in materials, proprietary chemicals and energy inputs. The impacts of AMD on laboratory-scale activated sludge units (plug-flow and sequencing batch reactors) treating synthetic MWW were investigated. Synthetic AMD containing Al, Cu, Fe, Mn, Pb, Zn and SO₄ at a range of concentrations and pH values was formulated to simulate three possible co-treatment processes, i.e., (1) adding raw AMD to the activated sludge aeration tank, (2) pre-treating AMD prior to adding to the aeration tank by mixing with digested sludge and (3) pre-treating AMD by mixing with screened MWW. Continuous AMD loading to the activated sludge reactors during co-treatment did not cause a significant decrease in chemical oxygen demand (COD), 5-day biochemical oxygen demand, or total organic carbon removal; average COD removal rates ranged from 87–93 %. Enhanced phosphate removal was observed in reactors loaded with Fe- and Al-rich AMD, with final effluent TP concentrations <2 mg/L. Removal rates for dissolved Al, Cu, Fe and Pb were 52–84 %, 47–61 %, 74–86 % and 100 %, respectively, in both systems. Manganese and Zn removal were strongly linked to acidity; removal from net-acidic AMD was <10 % for both metals, whereas removal from circum-neutral AMD averaged 93–95 % for Mn and 58–90 % for Zn. Pre-mixing with screened MWW was the best process option in terms of AMD neutralization and metal removal. However, significant MWW alkalinity was consumed, suggesting an alkali supplement may be necessary.     

酸碱联合调节剩余污泥对有机质的释放和脱水性能的影响

为了研究酸碱联合调节剩余污泥水解酸化过程中溶解性蛋白质(SPN)和溶解性碳水化合物(SPS)的释放规律以及对脱水性能的影响,采用3个反应器,其中,1#为先酸(pH 3.0)后碱(pH 10.0)、3#为先碱(pH 10.0)后酸(pH 3.0)的两段控制方式(每段8 d),同时以2#pH不调作为对比实验。结果表明,3个反应器中SPN和SPS的释放情况是调节为碱性>酸性>空白,在相同的控制阶段,SPN的释放量明显高于SPS的释放量;SPN和SPS的最大释放量出现在1#的碱性阶段(后8 d),SPN在碱性阶段的第2天达到最大释放量(883.618 mg/L),SPS在碱性阶段的第8天达到最大释放量(165.922 mg/L)。1#在实验的整个过程中比阻值较低,说明先酸后碱调节方式更利于污泥脱水;在调节为碱性第4天时污泥比阻(SRF)达到最小值(0.342×1013m/kg),处于中难度脱水范围内。与2#相比,3#中的SRF虽稍有改善,但始终处于难脱水范围内。     

Effective remediation of grossly polluted acidic, and metal-rich, spoil heap drainage using a novel, low-cost, permeable reactive barrier in Northumberland, UK

A permeable reactive barrier (PRB) for remediation of coal spoil heap drainage in Northumberland, UK, is described. The drainage has typical chemical characteristics of pH<4, [acidity]>1400 mg/L as CaCO3, [Fe]>300 mg/L, [Mn]>165 mg/L, [Al]>100mg/L and [SO4]>6500 mg/L. During 2 years of operation the PRB has typically removed 50% of the iron and 40% of the sulphate from this subsurface spoil drainage. Bacterial sulphate reduction appears to be a key process of this remediation. Treatment of the effluent from the PRB results in further attenuation; overall reductions in iron and sulphate concentrations are 95% and 67% respectively, and acidity concentration is reduced by an order of magnitude. The mechanisms of attenuation of these, and other, contaminants in the drainage are discussed. Future research and operational objectives for this novel, low-cost, treatment system are also outlined.     

负载TiO2/Fe3+的玻璃纤维反应器光催化苯酚

以玻璃纤维为载体,将TiO2负载到其表面形成了空间玻璃纤维反应器,引入Fe3+作为掺杂改性离子,形成了负载TiO2/Fe3+的空间玻璃纤维光催化反应器,并以高压汞灯为光源进行了光催化降解水中苯酚的实验研究,考察了影响苯酚光催化降解的因素,确定了在UV365～250 W光源照射下,pH为3～5,O2通入量1.0 L/(min.L),反应器内上升流速为0.7 m/min等实验条件下,初始浓度为30 mg/L的苯酚废水经120 min光催化反应后,降解率可达到85%,矿化率可达80%。     

方解石粉钝化太湖水中磷的能力及影响因素

利用轻质、重质和纳米方解石粉进行了去除太湖水中磷的实验研究,单位重量方解石粉除磷量与溶液中磷浓度正相关,轻质和重质方解石粉除磷规律符合Langmuir吸附等温式,极限除磷量分别为0.387 mg/g和0.351 mg/g,纳米方解石粉除磷规律符合Freundlich吸附等温式.方解石粉BET比表面积是影响方解石粉除磷能...     

Overcoming challenges to struvite recovery from anaerobically digested dairy manure

Recovering struvite from dairy manure has consistently posed problems for researchers. This study separated solids from anaerobically digested dairy manure using a filtration system. Filtrate was rich in free magnesium (160 to 423 mg/L), ammonium (320 to 1800 mg N/L) and orthophosphate (93 to 332 mg P/L). High concentrations of free calcium (128 to 361 mg/L) and alkalinity (3309 to 6567 mg/L as CaCO3), however, may hinder struvite precipitation. Batch precipitation tests were conducted to identify and overcome factors that interfere with struvite formation. Precipitation tests at pH 9 identified calcium and ionic strength as most probable interferences. Calcium addition did not significantly change phosphorus removal efficiency, but decreased struvite purity because of formation of calcium phosphates when Ca:P activity ratio was greater than 0.5 to 1. Batch tests demonstrated effective calcium removal from anaerobically digested dairy manure through precipitation of calcium carbonate at pH 9 to 10 while retaining magnesium and orthophosphate, lessening hindrance to struvite formation.     

Water quality and fish size affect toxicity of endosulfan, an organochlorine pesticide, to rainbow trout

The acute toxicity of endosulfan in juvenile rainbow trout (Oncorhynchus mykiss, 10.61+/-1.69 g) was evaluated in glass aquaria under static conditions. Nominal concentrations of endosulfan in the toxicity test ranged from 1.3 microg l(-1) to 29 microg l(-1). The concentrations of endosulfan that killed 50% of the rainbow trout within 24-h (24-h LC50), 48-h LC50, 72-h LC50, and 96-h LC50 were 19.78, 8.89, 5.28, and 1.75 microg l(-1), respectively. None of the unexposed control fish died, and the first fish died 4 h after exposure to 26.3 microg l(-1) of endosulfan. Survival of fish was significantly increased with increasing fish size and decreased with decreased fish size at the same temperature (p<0.001). Temperature also had a significant effect on survival of fish. Alkalinity at levels above 20 mg l(-1) as CaCO3 significantly increased survival of fish at 19.78 microg l(-1) of endosulfan. Increasing alkalinity from 20 mg l(-1) as CaCO3 to 42 or higher concentrations tested in this study (121 mg l(-1) as CaCO3) significantly increased survival of fish (p<0.01). Total hardness ranging from 55 mg l(-1) as CaCO3 to 126 mg l(-1) as CaCO3 did not affect survival of fish exposed to endosulfan. Endosulfan toxicity was found to be irreversible when fish were exposed to minimum concentrations of endosulfan tested. Histologically, fish gills had lamellar edema, separation of epithelium from lamellae, lamellar fusion, and swelling of the epithelial cells. Melanomacrophage centers were scattered throughout the trunk kidney, head kidney, and spleen. The liver of endosulfan-exposed fish had severe focal necrosis. None of these lesions were seen in unexposed control fish. Results indicate that alkalinity, temperature, and fish size affect endosulfan toxicity of rainbow trout.     

酸碱联合调节剩余污泥过程中氮、磷和有机质的释放

实现城市污泥的减量化和资源化是污水厂面临的难题之一。通过采用(1)先酸性(pH=3)后碱性(pH=10)、(2)先碱性(pH=10)后酸性(pH=3)的两段控制方式(每段反应8 d),同时做pH不调的对比实验,研究剩余污泥水解酸化过程中氨氮、磷酸盐和溶解性COD(SCOD)、碳水化合物、蛋白质和挥发性脂肪酸(VFAs)等有机质组分的释放。结果表明,酸碱联合调节有利于各组分的释放;氮和磷在酸性条件下的释放量大于碱性,有机质在碱性条件下的释放量大于酸性;采用(2)方式,调为酸性后反应1 d,氨氮的释放量即达到最大(17.28 mg/g TS);采用(1)的调节方式反应7 d,磷酸盐能达到最佳释放量(14.16 mg/g TS);总VFAs的产生受反应时间的影响较大,其余有机质组分在(2)的调节方式下,6 d左右即可达到较大释放量。     

混合硫酸盐还原菌代谢过程的影响因素

采用间歇实验,研究不同初始pH、Fe2+投加量、COD/SO24-及NO3-/SO24-比值等因素对SRB还原硫酸盐效果与速率的影响。实验结果表明:中性条件下(pH=7),硫酸盐的去除效果最佳,去除率达到84.66%,还原速率为15.07 mg/(L.h),在初始pH为4～9的范围内,体系具有较好的缓冲能力;当COD/SO24-比值为3时,反应209 h,硫酸盐去除率为85.33%,还原速率为8.16 mg/(L.h),随着反应的进行,体系的pH趋于中性;当溶液中有亚铁离子存在,且浓度为0～200 mg/L时可促进硫酸盐还原菌的生长,提高其对硫酸盐的去除率;NO3-对硫酸盐的还原有明显的抑制作用。     

改性活性炭对石煤提钒废水中低浓度NH_3-N和V等的吸附

为研究石煤提钒离交尾水的深度处理技术,利用质量分数为1%、5%和10%的过氧化氢溶液对ZWY15型活性炭进行改性,得到3种改性活性炭即1%AC、5%AC和10%AC;探讨其对该废水中低浓度的NH3-N、V等的吸附效果。实验结果表明：AC或改性AC的加入可使废水的碱度升高,随着吸附时间及吸附剂投加量的增加,升高幅度增大,且不同改性AC对废水碱度提高的幅度不同;相较于未改性活性炭,过氧化氢改性活性炭对V的吸附效果明显提高,去除率最大可提高30%,对NH3-N的去除率提升约11%;当投加量为60 g/L时,10%AC可使废水中V的浓度降低至1.88 mg/L,此时废水中Cr、Cd和Zn的浓度分别降低至0.006、0.010和0.036 mg/L,均低于《钒工业污染物排放标准》（GB26452-2011）所规定的排放限值。     

Fe3O4/SDS磁性纳米颗粒吸附水体中的Cd2+和Zn2+

一种新型纳米固相萃取吸附剂,由阴离子表面活性剂十二烷基磺酸钠(SDS)包裹在Fe3O4磁性纳米颗粒表面形成,用于吸附水溶液中的重金属离子。研究了吸附过程的主要影响因素(如SDS浓度、溶液pH等)以及解吸过程的最佳条件,并对其机理进行了初步的探讨。研究结果表明,共沉淀法制备的Fe3O4颗粒粒径分布均匀,平均粒径约为54 nm;SDS浓度为300 mg/L时,Fe3O4/SDS磁性纳米颗粒吸附Cd2+和Zn2+的能力最强;在一定浓度范围内,Fe3O4/SDS体系对Cd2+和Zn2+的吸附平衡数据符合Langmuir吸附等温方程,饱和吸附量分别为22.42 mg/g和13.95 mg/g。最终结果表明,Fe3O4/SDS磁性纳米颗粒具有较强磁分离能力和较好的吸附效果。     

Trout farm effluents: characterization and impact on the receiving streams

Effluents from three rainbow trout (Oncorhynchus mykiss) farms located in Northern Portugal were characterized and their impact on the receiving streams was evaluated. Mean fish productions in the studied fish farms were 15, 55 and 500 t of trout per year, respectively. The feeding water was abstracted from Fornelo, Inha and Coura Rivers, at flow rates ranging from 1.2 (15 t year(-1) fish farm) to 4.8 litre s(-1) per ton annual fish production (500 t year(-1) fish farm). As the water flows through the farms, net variations in the chemical characteristics were observed: a mean reduction in the dissolved oxygen (DO) concentration between 0.7 and 2.4 mg litre(-1); mean increases between 1.9 and 3.2 mg CaCO3 litre(-1) for total alkalinity, between 0.9 and 14 mg litre(-1) for BOD5, between 0.27 and 1.46 mg litre(-1) for ammonia nitrogen (NH4-N), between 0.060 and 0.579 mg litre(-1) for soluble phosphorus (PO4-P) and less than 16 mg litre(-1) for suspended solids; variations in the pH value and nitrate nitrogen concentration were not statistically significant (p<0.05). At the 500 t year(-1) fish farm it was also possible to detect net increases of total hardness (3.2 mg CaCO3 litre(-1)), electric conductivity (19 mS cm(-1)) and permanganate value (3.6 mgO2 litre(-1)). At the other farms net variations in these parameters were not significant. Net mass flow variations reported to the annual fish production are presented. The DO mass flow decreased, on average, between 255 and 549 g t(-1) of fish per day. The mean daily BOD5 increase ranged from 353 to 1510 g t(-1) of fish. The corresponding ranges for the other parameters were 105-157 g t(-1) for NH4-N, 24-62 g t(-1) for PO4-P, 348-1035 g CaCO3 t(-1) for total alkalinity and 224 x 10(6)-506 x 10(6) t(-1) for mesophilic bacteria. Daily net variations of suspended solids, total hardness, electric conductivity and permanganate value were below 1753 g t(-1), 342 g CaCO3 t(-1), 2081 mS cm t(-1) and 392 gO2 t(-1), respectively. Longitudinal concentration profiles for the most relevant parameters show the impact of the effluent discharges on the physico-chemical and bacteriological river water quality downstream from the trout farms. Analyzing the situations from a purely chemical point of view, the polluted stretches were 3, 5 and 12 km long downstream from the effluent discharges, respectively. The microbiological contamination extended over longer distances.     

改性活性炭对石煤提钒废水中低浓度NH3-N和V等的吸附

为研究石煤提钒离交尾水的深度处理技术,利用质量分数为1%、5%和10%的过氧化氢溶液对ZWY15型活性炭进行改性,得到3种改性活性炭即1%AC、5%AC和10%AC;探讨其对该废水中低浓度的NH3-N、V等的吸附效果。实验结果表明:AC或改性AC的加入可使废水的碱度升高,随着吸附时间及吸附剂投加量的增加,升高幅度增大,且不同改性AC对废水碱度提高的幅度不同;相较于未改性活性炭,过氧化氢改性活性炭对V的吸附效果明显提高,去除率最大可提高30%,对NH3-N的去除率提升约11%;当投加量为60 g/L时,10%AC可使废水中V的浓度降低至1.88 mg/L,此时废水中Cr、Cd和Zn的浓度分别降低至0.006、0.010和0.036 mg/L,均低于《钒工业污染物排放标准》(GB26452-2011)所规定的排放限值。     

Comparison of benthic macroinvertebrate indices for the assessment of the impact of acid mine drainage on an Irish river below an abandoned Cu-S mine

A range of macroinvertebrate indices were compared to assess the most appropriate metric for the assessment of acid mine drainage (AMD) in a low alkalinity, highly erosional river in south-east Ireland. Differences were found in the ability of indices to discriminate AMD impact with the Brillouin, BMWP score, Margalef and Shannon Indices the most precise. Taxon richness was also strongly correlated with AMD indicator parameters (e.g. pH alkalinity, sulphate, Zn and Fe) at impacted sites being an equally reliable metric. The response of the community structure to AMD in this river does not fulfil the optimum criteria for either diversity or biological indices, which may explain the variation in the success of different indices seen in this and other studies. The development of indices that model the expected community response to AMD more accurately or are based on the response of indicator species to AMD pollutants are required.     

Photocatalytic oxidation of NOx using composite sheets containing TiO2 and a metal compound

The photocatalytic oxidation of nitrogen oxides (NO(x)) over titanium dioxide (TiO(2)) sheets containing metal compounds (MCs) had been studied. Calcium oxide (CaO), magnesium oxide (MgO), calcium carbonate (CaCO(3)), aluminium oxide (Al(2)O(3)) and ferric oxide (Fe(2)O(3)) were used as MCs. Al(2)O(3) and Fe(2)O(3) added to the TiO(2) sheet did not affect the photooxidation of nitrogen oxides (NO(x)). The CaO sheet treated with TiO(2) sol had the greatest efficiency as a NO(x) remover under UV irradiation. It is believed that CaO has a high adsorptivity for nitrogen dioxide (NO(2)) and nitric acid (HNO(3)). The amount of NO(x) removed by a TiO(2) sheet including MC showed a tendency to increase with increasing pH of the MC suspension, i.e. there is a good correlation between the alkalinity of the MC and the retention of NO(2) and HNO(3).     

Fenton's pre-treatment of mature landfill leachate

The aim of this study was to check the effectiveness of the Fenton's reagent (Fe2+ + H2O2 + H+) for the pre-treatment of a municipal landfill leachate with the objective of improving its overall biodegradability, evaluated in terms of BOD5/COD ratio, up to a value compatible with biological treatment. The leachate came from a municipal sanitary landfill located in southern Italy and the average values of its main parameters were: pH=8.2; COD=10,540 mgl(-1); BOD5=2,300 mgl(-1); TOC=3,900 mgl(-1); NH4-N=5210 mgl(-1); conductivity=45,350 microScm(-1); alkalinity=21,470 mgl(-1) CaCO3. The effect of initial pH value on the pre-treatment effectiveness was evaluated by titrating the amount of acidic by-products formed. The extent of leachate oxidation was monitored and controlled by both pH and redox potential measurements. The best operational conditions for achieving the desired goal (i.e., BOD5/COD> or =0.5) resulted: Fe2+=275 mgl(-1); H2O2=3,300 mgl(-1); initial pH=3; reaction time=2 h. At the end of the Fenton's pre-treatment, in order to permit a subsequent biological treatment, residual ferric ions were removed increasing the pH up to 8.5 by adding 3 gl(-1) of Ca(OH)2 and 3 mgl(-1) of a cationic polyelectrolyte, the latter as an aid to coagulation. This final step also resulted in a further modest removal of residual COD due to co-precipitation phenomena.     

养殖污水生物处理的新型流态化技术原理及其应用案例

以COD、NH4+-N、SS值高以及臭味大的水质特征的养殖污水作为研究对象,针对一般处理模式中的生物反应器存在污泥相停留时间短、耐负荷冲击能力低、除碳与脱氮不能协调以及投资运行费用大等问题,自行研制了具有强化传质与混合功能的射流循环厌氧与气升循环好氧流态化反应器,实现了A/O2的组合生物强化工艺,再辅以预处理与后处理工艺,实践了规模为216 m3/d的工程设计与运行,通过连续6个月的运行数据来评价所提出工艺的工程效果。在A、O1与O2的运行负荷(kg COD/(m3.d))分别为6、6及0.5的近似条件下,当进水COD、BOD5、NH 4+-N和SS浓度分别为11 000～13 000、5 500～6 500、560～640和7 000～9 000 mg/L时,处理后出水浓度分别可降低至56.8～59.2、4.7～4.9、8.6～9.5和37.0～39.4 mg/L,各项指标均达到《广东省水污染物排放限值》(DB4426-2001)第2时段的一级排放标准限值要求,取得了明显的工程实效,表明所开发的技术有推广应用的价值。     

Catalytic hydrolysis of urea from wastewater using different aluminas by a fixed bed reactor

In order to find an effective method for treating urea wastewater, the experiments on the hydrolysis of urea in wastewater were conducted in a fixed bed reactor with different aluminas (α-Al₂O₃, γ-Al₂O₃, and η-Al₂O₃) as catalysts respectively in contrast with inert ceramic particle. The results indicate that the three alumina catalysts show obvious catalytic activity for urea hydrolysis at 125 °C. The order of activity is η-Al₂O₃?>?γ-Al₂O₃?>?α-Al₂O₃, and the activity difference increases with increasing temperature. According to the characterization results, surface acidity has little impact on the activity of catalyst. However, it was found that surface basicity of alumina catalyst plays an important role in catalytic hydrolysis of urea, and the activity of catalyst may be also influenced by the basic strength. With η-Al₂O₃ as catalyst, the urea concentration in wastewater is reduced to 4.96 mg/L at a temperature of 165 °C. Moreover, the η-Al₂O₃ shows a good stability for urea hydrolysis. The hydrolysis of urea over η-Al₂O₃ catalyst can evidently reduce the reaction temperature and is promising to replace industrial thermal hydrolysis process.     

水解-好氧生物法处理城市污水试验研究

采用水解 好氧工艺的原理 ,设计了将污水与污泥处理合二为一的高效组合水解池 三相生物流化床流程 ,在广州经济技术开发区进行了处理量为 1 0 0L/h的城市污水处理试验。试验结果表明 :在平均进水CODCr为 4 92 3mg/L ,BOD5为 2 4 0 9mg/L ,SS为 5 5 2 3mg/L ,NH4 N为 1 8 8mg/L ,TP为 2 0mg/L条件下 ,平均出水CODCr为 4 7 3mg/L ,BOD5为 2 2 lmg/L ,SS为 1 3 9mg/L ,NH4 N为 5 2mg/L ,TP为 1 4mg/L ,并进行了该工艺中污泥循环的初步分析 ,为该工艺处理城市污水工业化提供了技术参考。     

Removal of chromium from abrasive blast media by leaching and electrochemical precipitation

Water is effective in leaching out Cr6+ from a mixture of paint powders and abrasive blast media. However, acids such as HNO3, HCl, and H2SO4 significantly enhance the leaching procedure. Cr ions in the leaching solutions are successfully removed by electrochemical precipitation. The consumable Fe electrodes generate ferrous ions to cause the reduction of Cr6+ to Cr3+. Cr3+ ions along with Fe2+ and Fe3+ are then removed mainly by precipitation as Cr(OH)3, Fe(OH)2, and Fe(OH)3 near the cathode where OH- ions are generated by water electrolysis. The electrochemical process is capable of discharging low levels of Cr6+, less than 1 mg/L, without pH adjustment.