Effects of nitrosation on the formation of cyanide in publicly owned treatment works secondary effluent.

Cyanide has been detected in the effluents of some publicly owned treatment works (POTWs) at levels exceeding the influent concentration. The presence of nitrite ion (NO2-) as a common constituent in domestic wastewater effluents may play an important role in the formation of cyanide through reaction with certain kinds of organic compounds, especially aromatic compounds. Laboratory studies with seven organic compounds (aniline. p-toluidine, phenol, 1,2,4-trihydroxybenzene, L-serine, glycine, and benzoic acid) revealed that cyanide can be formed by reaction of nitrite with some of these compounds. The most substantial free cyanide (HCN. CN-) production observed at 25 degrees C was 0.15 mg/L from reaction of 0.01 mM 1.2.4-trihydroxybenze with 5 mg/L nitrite for 72 hours. Substantial free cyanide formation was also observed at pH 2-4 in experiments with POTW effluents when reactive organics and nitrite were both added to wastewater. Formation of cyanide through nitrosation was strongly pH dependent, being most significant at low pH (2 to 4) and negligible at neutral-to-high pH. This result points to nitrous acid (HNO2) as being more reactive than the dissociated NO2- ion. The reaction of these nitrite species with organics also occurs in conventional analyses for total cyanide which involve distillation under strongly acidic conditions. Sufficient sample pretreatment with sulfamic acid at the time of sampling, not at the time of analysis. is highly recommended to prevent biasing analytical measurement of total cyanide in POTW effluents.     

Effects of thiocyanate on the formation of free cyanide during chlorination and ultraviolet disinfection of publicly owned treatment works secondary effluent.

Cyanide has been detected in effluent of some publicly owned treatment works (POTWs) at levels exceeding influent concentration. Thiocyanate (SCN-) is a cyanide-related compound encountered in most POTW influents and may be decomposed to free cyanide (CN-) under some circumstances. Effects of SCN- on the formation of cyanide during chlorination and UV disinfection were studied through a laboratory study with synthetic solutions and POTW secondary effluent. Results indicated that CN- was detected in SCN- solutions after chlorination in which the chlorine dose or reaction time was not sufficient to destroy SCN-completely, thus ensuring no residual chlorine to destroy any CN-produced. It was also found that SCN can be broken down to yield cyanide by UV irradiation. In addition, SCN- was observed to cause significant positive error in the conventional total cyanide analysis technique involving acidic distillation and colorimetric measurement when nitrate was present in the sample.     

亚铁蓝法处理含氰废水的工程应用

文中综述了氰化物的危害和含氰废水的来源以及目前处理含氰废水的方法。以工程实例重点介绍亚铁蓝法处理此废水的应用。亚铁蓝法除氰可分二级进行,第一级在中性条件总氰去除率达到80%以上,第二级直接在一级出水加碱调pH至8～9沉淀即可,通过二级处理总氰去除率达到95%左右。     

Formation of free cyanide and cyanogen chloride from chloramination of publicly owned treatment works secondary effluent: laboratory study with model compounds.

The potential generation of cyanide species in wastewater upon chlorination in the presence of residual ammonia (resulting in chloramine formation) was investigated in experiments with synthetic solutions and publicly owned treatment works (POTW) secondary effluent. This study demonstrated that low concentrations (approximately 5 to 25 microg/L as cyanide) of cyanogen chloride (CNCI), a highly toxic cyanide species not measured in total or free cyanide analyses, could be detected as a result of chloramination reactions in POTW secondary effluent. The potential for chloramination of nitrogen-bearing organic compounds to yield CNCl and/or free cyanide was demonstrated in experiments with synthetic solutions spiked with selected precursor organics: L-serine, benzene, catechin, and humic acid. The amino acid L-serine yielded the largest concentrations of CNCI upon chloramination. Additionally, detectable cyanide (approximately 10 microg/L) was observed in solutions of L-serine and in POTW secondary effluent that was chloraminated followed by dechlorination to prevent destruction of any free cyanide produced. Thus, chlorination of POTW secondary effluent containing residual ammonia can lead to chloramination of organic compounds and the resulting production of CNCl and free cyanide.     

电混凝处理电镀综合废水

采用电混凝法处理酸性电镀综合废水,首先研究了不同电流密度对总氰化物、重金属和化学需氧量（COD）去除率的影响。实验结果表明,电混凝可有效去除酸性电镀综合废水中的氰化物与重金属。随着电流密度的增大,总氰化物与重金属的去除率逐渐提高。当电流密度为10mA／cm2时,废水中残留的总氰化物、Cu2＋、Ni2＋、Cr6＋和Zn2＋ 的浓度分别为23．0、25．0、4．5、0．2和0．2mg／L。为了进一步提高去除率,在电化学体系中添加H2O2,随着H2O2投量的增大,总氰化物、重金属、COD去除率不断提高。当H2O2投量为3mL／L时,处理过废水中残留总氰化物、Cu2＋、Ni2＋、Cr6＋、Zn2＋和COD的浓度分别为0．2、2．0、3．0、1．5、0．1和220mg／L。     

The occurrence of cyanide formation in six full-scale publicly owned treatment works.

This paper presents results from an intensive monitoring program implemented at six full-scale publicly owned treatment works (POTWs) to investigate the fate and formation of cyanide in wastewater treatment processes, with a focus on chlorination and dechlorination processes. A review of historical monitoring data for cyanide species in these POTWs was also conducted. This POTW monitoring program provided a database for the investigation of cyanide formation in wastewater secondary treatment. Data from participating POTWs showed evidence of cyanide formation in this 1-year monitoring effort, although the cyanide formation pattern varied significantly from one plant to another and among seasons. Generally, the chlorination of thiocyanate (SCN-) seems to be the most important mechanism for the formation of cyanide in wastewater treatment processes, especially in chlorination and dechlorination. This hypothesis is supported by the findings of a related laboratory study of mechanisms of cyanide formation in POTWs. It is recommended that POTWs monitor SCN in influent and secondary effluent to identify its presence and adjust chlorine dose appropriately.     

High levels of activity of bats at gold mining water bodies: implications for compliance with the International Cyanide Management Code

Wildlife and livestock are known to visit and interact with tailings dam and other wastewater impoundments at gold mines. When cyanide concentrations within these water bodies exceed a critical toxicity threshold, significant cyanide-related mortality events can occur in wildlife. Highly mobile taxa such as birds are particularly susceptible to cyanide toxicosis. Nocturnally active bats have similar access to uncovered wastewater impoundments as birds; however, cyanide toxicosis risks to bats remain ambiguous. This study investigated activity of bats in the airspace above two water bodies at an Australian gold mine, to assess the extent to which bats use these water bodies and hence are at potential risk of exposure to cyanide. Bat activity was present on most nights sampled during the 16-month survey period, although it was highly variable across nights and months. Therefore, despite the artificial nature of wastewater impoundments at gold mines, these structures present attractive habitats to bats. As tailings slurry and supernatant pooling within the tailings dam were consistently well below the industry protective concentration limit of 50 mg/L weak acid dissociable (WAD) cyanide, wastewater solutions stored within the tailings dam posed a minimal risk of cyanide toxicosis for wildlife, including bats. This study showed that passively recorded bat echolocation call data provides evidence of the presence and relative activity of bats above water bodies at mine sites. Furthermore, echolocation buzz calls recorded in the airspace directly above water provide indirect evidence of foraging and/or drinking. Both echolocation monitoring and systematic sampling of cyanide concentration in open wastewater impoundments can be incorporated into a gold mine risk-assessment model in order to evaluate the risk of bat exposure to cyanide. In relation to risk minimisation management practices, the most effective mechanism for preventing cyanide toxicosis to wildlife, including bats, is capping the concentration of cyanide in tailings discharged to open impoundments at 50 mg/L WAD.     

Management options and effects on a marine ecosystem: assessing the future of the Baltic

We are using the coupled models in a decision support system, Nest, to evaluate the response of the marine ecosystem to changes in external loads through various management options. The models address all the seven major marine basins and the entire drainage basin of the Baltic Sea. A series of future scenarios have been developed, in close collaboration with the Helsinki Commission, to see the possible effects of improved wastewater treatment and manure handling, phosphorus-free detergents, and less intensive land use and live stocks. Improved wastewater treatment and the use of phosphorus-free detergents in the entire region would drastically decrease phosphorus loads and improve the marine environment, particularly the occurrence of cyanobacterial blooms. However, the Baltic Sea will remain eutrophic, and to reduce other effects, a substantial reduction of nitrogen emissions must be implemented. This can only be obtained in these scenarios by drastically changing land use. In a final scenario, we have turned 50% of all agricultural lands into grasslands, together with efficient wastewater treatments and a ban of phosphorus in detergents. This scenario will substantially reduce primary production and the extension of hypoxic bottoms, increase water transparency in the most eutrophied basins, and virtually eliminate extensive cyanobacterial blooms.     

Cyanide generation during preservation of chlorinated wastewater effluent samples for total cyanide analysis.

Dechlorinating agents and pH adjustment are often used to preserve wastewater samples for cyanide analysis. The effects of four approved preservation protocols on the results of the total cyanide analysis of effluents from four water reclamation plants were examined. The results differed widely, and a clear pattern emerged. Immediate analysis without pH adjustment generally gave total cyanide concentrations below the reporting limit of 5 microg/L, irrespective of the dechlorinating agents used. When the pH was adjusted to > or =12, a slight increase in the measured total cyanide concentration was observed when thiosulfate was used to dechlorinate the samples, and a significant increase (>10 microg/L) was observed when arsenite was used as the dechlorinating agent. These results provide evidence that approved preservation protocols may give rise to cyanide formation in chlorinated wastewater effluent matrices.     

炼焦废水生化处理技术研究进展

综述了近几年来炼焦废水及炼焦废水中主要成分(酚类、氨类物质、氰化物)的生化处理方法.其中废水中酚类物质的去除方法有投加有效菌、超滤法等;去除氨类物质的方法有A2/O法、纳滤法和反渗透法等;去除氰化物的方法有生物法和化学法等.综合处理炼焦废水的方法有双层生物膜法、生物脱氮法和含铁活性污泥处理技术等.     

Microbial degradation of metal complexed cyanides and thiocyanate from mining wastewaters

A microbiological examination of the soil from a cyanide wastewater storage basin was carried out. The storage basin contained water from the cyanidation process of gold extraction, and it was composed principally of simple cyanide, metal complexed cyanide, mainly cuprocyanide, ferro-ferricyanides and thiocyanate. Pseudomonas species were the principal bacteria identified in the soil. Using the storage basin soil as a seed sludge, its potential for the biodegradation of all the cyanide complexes in the mining wastewater was studied in the laboratory, using batch, fed-batch and continuous processes. The ammonia and sulphate produced were quantified. The presence of intermediate products was suspected. In the continuous process, total degradation of all cyanide was observed at a dilution rate of 0.066 day(-1).     

城市污水再生处理过程中壬基酚的迁移转化行为研究

采用SPE-GC-MSD-SIM方法,分析了壬基酚在污水再生处理全过程中的迁移转化行为与归宿.研究表明,在污水二级生物处理流程中,壬基酚主要来源为原污水和泥区回流液;壬基酚的去除途径有一沉池生污泥的吸附迁移作用和曝气池单元的生物降解转化作用,其中一沉池生污泥的吸附去除29.8%,曝气池生物降解54.4%,NP总去除率为84.2%.絮凝、过滤和消毒的污水再生深度处理工艺对壬基酚的迁移转化作用不明显.     

Predicting diffuse-source transfers of surfactants to surface waters using SWAT

Chemicals present in domestic wastewater can adsorb to solid phase materials during sewage treatment. If biosolids (or sewage sludge) are applied to land, these chemicals can be transferred to soil. Under some circumstances they can also be transferred to surface waters during storm events either in solution or attached to sediment. In this paper we describe the utility of the SWAT 2000 model to estimate diffuse-source surface water exposure to "down-the-drain" chemicals. The model was applied hypothetically to predict the behaviour of linear alkylbenzene sulphonate (LAS), an anionic surfactant commonly used in household detergents, in a small catchment in Bedfordshire, UK, where it has previously been successfully validated for stream flow, sediments and pesticides. LAS transfers were estimated for two scenarios: (1) realistic and (2) reasonable worst case, based on assumptions on sludge application rates and the concentration of LAS in sludge. In addition, the sensitivity of the model output to the proportion of the catchment to which sludge is applied was established. Soil wetness and the total quantity of biosolids applied were the biggest determinants of chemical transport from the catchment. The potential of SWAT as a higher-tier tool in environmental risk assessments is discussed.     

螺旋藻和菌-藻共生系统处理啤酒废水

利用螺旋藻、由真菌和螺旋藻组成的菌-藻共生系统处理啤酒废水,旨在为啤酒废水的资源化利用提供一条可行的途径。由螺旋藻和真菌形成的菌丝球组成菌-藻共生系统处理啤酒废水,与螺旋藻单独处理废水作对比,比较两者的废水净化效果以及螺旋藻的生长情况。从2组实验对比情况来看,菌-藻共生系统对啤酒废水的处理效果更好。螺旋藻和菌．藻共生系统对啤酒废水中几种主要污染物的去除率分别为：COD70．59％和77．81％,TN70．17％和84．28％,TP37．99％和50．88％。螺旋藻在废水中生长积累的蛋白质含量最高可达49．71％,明显高于在Zarrouk培养基中的螺旋藻蛋白含量（38．57％）。研究结果表明,螺旋藻及菌-藻共生系统对啤酒废水有较好的净化作用,所得螺旋藻生物质可用于加工饲料、饵料、色素的提取等。     

Determination of antibiotic compounds in water by on-line SPE-LC/MSD

This study attempts to provide an improved approach for the analysis of antibiotics, which normally exist at low concentration in complex matrices such as receiving streams of wastewater treatment plant discharge. The analytical method developed in this study combines an existing pretreatment technique of solid-phase extraction (SPE) with liquid chromatography mass spectrometry (LC/MSD) through on-line connection. The on-line connection suppressed the target loss by keeping the cartridge from drying, which resulted in improvement of the recovery and saving of the analytical time. For the on-line solid-phase extraction of 10 ml water samples, recoveries were between 74.3% and 116.5% and average LOQ was 0.11 microg l(-1) for the sulfonamide antibiotics (SA) and 0.09 microg l(-1) for the tetracycline antibiotics (TA). Application of the developed method for the analysis of fourteen antibiotics revealed that several antibiotics were detected at concentrations above the LOQ in ARW. Treated and untreated sewage and agricultural wastewater were mostly responsible for the antibiotics contamination of the river. Antibiotics were detected at much higher concentrations in the agricultural wastewater sample than in the sewage sample, implying substantial use of antibiotics in the agricultural industry. Wastewater treatment was generally effective in separation of the antibiotics tested in this study. The extent of the treatment depended on the type of antibiotics. Hydrophobic antibiotics were more effectively separated from the solution than hydrophilic antibiotics.     

RO/NF membrane treatment of veterinary pharmaceutical wastewater: comparison of results obtained on a laboratory and a pilot scale

Background  

Emerging contaminants (ECs) are commonly derived from industrial wastewater, which is often a consequence of an inadequate treatment of the latter. Improperly pretreated pharmaceutical wastewater could cause difficulties in operations of wastewater treatment plants while incomplete elimination of ECs during the processing might result in their appearance in drinking water.     

异烟酸-吡唑啉酮显色液的改进

对异烟酸-吡唑啉酮光度法测定水和废水中氰化物的方法进行了改进。在不改变其它步骤的前提下,以去离子水代替二甲基甲酰胺所配制的吡唑啉酮溶液及异烟酸溶液作为显色剂。试验结果表明,改进后的新方法精密度RSD〈5％,加标回收率为92．0％～105．0％,通过电镀废水和标准样品的比对试验表明,改进后的方法与标准方法对同一样品的测定结果无显著性差异,满足监测分析要求。     

Assessment of the effluent quality from a gold mining industry in Ghana

The physical and chemical qualities of the process effluent and the tailings dam wastewater of AngloGold-Ashanti Limited, a gold mining company in Ghana, were studied from June to September, 2010. The process effluent from the gold extraction plant contains high amounts of suspended solids and is therefore highly turbid. Arsenic, copper and cyanide were identified as the major pollutants in the process effluent with average concentrations of 10.0, 3.1 and 21.6 mg?L^?1, respectively. Arsenic, copper, iron and free cyanide (CN^?) concentrations in the process effluent exceeded the Ghana EPA discharge limits; therefore, it is necessary to treat the process effluent before it can be discharged into the environment. Principal component analysis of the data indicated that the process effluent characteristics were influenced by the gold extraction process as well as the nature of the gold-bearing ore processed. No significant correlation was observed between the wastewater characteristics themselves, except for the dissolved oxygen and the biochemical oxygen demand. The process effluent is fed to the Sansu tailings dam, which removes 99.9 % of the total suspended solids and 99.7 % of the turbidity; but copper, arsenic and cyanide concentrations were still high. The effluent produced can be classified as inorganic with a high load of non-biodegradable compounds. It was noted that, though the Sansu tailings dam stores the polluted effluent from the gold extraction plant, there will still be serious environmental problems in the event of failure of the dam.     

Aerobic Treatment of a Nitrogen-Limited Chemical Process Waste water

Abstract

Nitrogen transformations and their effect on aerobic suspended growth treatment of an industrial wastewater were studied in three parallel bench-scale reactors operated at 5 "C at mean cell residence times (MCRT) of 15, 30, and 60 days. In normal process wastewater, the bulk of influent nitrogen was in organic form, and the fraction transformed was almost totally incorporated into synthesized biomass. Assimilative control by heterotrophs maintained ammonianitrogen levels below permitted effluent levels, and nitrification was not significant. Although volatile suspended solids had a nitrogen content of only 5% to 8%, effective organics removal was maintained, and total organic carbon and filtered daily average five-day biochemical oxygen demand (BODS) were below permitted effluent levels. A marked improvement in settleability and lower effluent total suspended solids was achieved by adding ammonia-nitrogen to the wastewater in excess of stoichiometric growth requirements.

During a batch production cycle of a cationic chemical, the ratio of nitrogen to chemical oxygen demand and the fraction of the total influent nitrogen in soluble form increased in the wastewater. Reactor effluent ammonia levels increased to above permit levels at all three MCRTs during treatment of wastewater containing cationic production effluents. The magnitude of ammonia increase was greater for longer MCRTs, suggesting that synthesis of cell mass was not capable of assimilating the increased ammonia supply under these non-steady conditions. The experimental results suggest several potential strategies for operating the aerobic process at the treatment facility, including adding nitrogen to improve settleability and discontinuing these additions when wastewater contains a high ratio of nitrogen to chemical oxygen demand and an elevated soluble nitrogen fraction     

Biotransformation of cyanide to methane and ammonia by Klebsiella oxytoca

Klebsiella oxytoca, isolated from cyanide-containing industrial wastewater, was shown to be able to biodegrade cyanide to non-toxic endproducts using cyanide as the sole nitrogen source. In this study, ammonia was one of the detected endproduct of cyanide biodegradation by the concentrated resting cells of K. oxytoca. Moreover, cyanide has been shown to be biotransformed to methane through the actions of concentrated resting cells. Biodegradation of cyanide by cell-free extracts was not observed, which might be due to the inactivation of nitrogenase (an oxygen-labial enzyme) caused by the oxygen exposure after cell disruption. Results show that the cyanide consumption by resting cells of K. oxytoca was induced when the pretreatment of these cells with cyanide was conducted. However, the cyanide-degrading capability of resting cells pretreated with ammonia was inhibited. The inhibition of cyanide degradation by resting cells of K. oxytoca was affected by the ammonia concentration. This might result from the suppression of nitrogenase activity of K. oxytoca by ammonia since nitrogenase was suggested to be the sole cyanide-degrading enzyme during the cyanide degradation process. Results from this study also show that the processes of cyanide biodegradation and ammonia production by resting cells occurred simultaneously. This suggests that the utilization of cyanide as nitrogen source by K. oxytoca might proceed using ammonia as an assimilatory substrate.