Significance and behaviour of heavy metals in waste water treatment processes I. Sewage treatment and effluent discharge

The literature concerning the significance and behaviour of heavy metals in waste waters is reviewed. Factors influencing the partition of heavy metals between the solid and liquid phases in both primary and secondary (biological) treatment are considered in detail. It is evident that during primary treatment only metals present in an insoluble form will be removed, but the removal of such forms is strongly influenced by the factors controlling sedimentation. During secondary treatment metals initially present as soluble forms may be removed by association with the settleable biomass: further removal of insoluble metals also occurs by association with this biomass. Efficient flocculation and settling is critical to the removal of all metal forms during secondary treatment. Extracellular material, principally bacterial extracellular polymers, but also proteins and nucleic acids released as the result of cell lysis, appear to play a very significant role in the removal of soluble metals during secondary treatment.If biological treatment plants are overloaded with metals, toxic effects on bacteria and other micro-organisms may result in poor quality effluents; although the micro-organisms responsible for waste water treatment are able, within limits, to acclimatise to elevated metal concentrations.The impact of heavy metal contaminated effluents on receiving waters has also been reviewed and it is concluded that the most serious problem posed is drinking water production in areas where water re-use is practised.     

Removal of metals by chemical treatment of municipal waste water

The reduction of the metal content of waste water by chemical treatment with aluminium sulfate or calcium hydroxide has been studied. p] Pb(II), Cu(II), Cr(III), Hg(II), Cd(II) and As(V) are reduced to low levels by both precipitants. Zn(II), Ni(II) and Co(II) are precipitated only at pH-values ≤ 9·5. The precipitation of Cu(II) and Pb(II) is greatly inhibited by the presence of nitrilotriacetate at pH ≤9.     

重金属污染废水微生物处理机制及其研究进展

从微生物对重金属离子的转化机制、吸附机制、絮凝机制等方面阐述了微生物法去除废水中重金属离子的基本原理,并对其研究进展及未来的主要研究方向进行了综述,指出微生物法具有良好的生态效益和应用前景。     

Implications of safety requirements for the treatment of THMC processes in geological disposal systems for radioactive waste

The mission of nuclear safety authorities in national radioactive waste disposal programmes is to ensure that people and the environment are protected against the hazards of ionising radiations emitted by the waste.It implies the establishment of safety requirements and the oversight of the activities of the waste management organisation in charge of implementing the programme.In Belgium,the safety requirements for geological disposal rest on the following principles:defence-in-depth,demonstrability and the radiation protection principles elaborated by the International Commission on Radiological Protection(ICRP).Applying these principles requires notably an appropriate identification and characterisation of the processes upon which the safety functions fulfilled by the disposal system rely and of the processes that may affect the system performance.Therefore,research and development(RD)on safety-relevant thermo-hydro-mechanical-chemical(THMC)issues is important to build confidence in the safety assessment.This paper points out the key THMC processes that might influence radionuclide transport in a disposal system and its surrounding environment,considering the dynamic nature of these processes.Their nature and significance are expected to change according to prevailing internal and external conditions,which evolve from the repository construction phase to the whole heatingecooling cycle of decaying waste after closure.As these processes have a potential impact on safety,it is essential to identify and to understand them properly when developing a disposal concept to ensure compliance with relevant safety requirements.In particular,the investigation of THMC processes is needed to manage uncertainties.This includes the identification and characterisation of uncertainties as well as for the understanding of their safety-relevance.RD may also be necessary to reduce uncertainties of which the magnitude does not allow demonstrating the safety of the disposal system.     

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.     

The behaviour of pharmaceuticals and heavy metals during struvite precipitation in urine

Separating urine from wastewater at the source reduces the costs of extensive wastewater treatment. Recovering the nutrients from urine and reusing them for agricultural purposes adds resource saving to the benefits. Phosphate can be recovered in the form of struvite (magnesium ammonium phosphate). In this paper, the behaviour of pharmaceuticals and heavy metals during the precipitation of struvite in urine is studied.When precipitating struvite in urine spiked with hormones and non-ionic, acidic and basic pharmaceuticals, the hormones and pharmaceuticals remain in solution for more than 98%.For heavy metals, initial experiments were performed to study metal solubility in urine. Solubility is shown to be affected by the chemical conditions of stored and therefore hydrolysed urine. Thermodynamic modelling reveals low or very low equilibrium solute concentrations for cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb). Experiments confirmed Cd, Cu and Pb carbonate and hydroxide precipitation upon metal addition in stored urine with a reaction half-life of ca. 7 days.For all metals considered, the maximum specific metal concentrations per gram phosphate or nitrogen showed to be typically several orders of magnitudes lower in urine than in commercially available fertilizers and manure. Heavy metals in struvite precipitated from normal stored urine could not be detected.Phosphate recovery from urine over struvite precipitation is shown to render a product free from most organic micropollutants and containing only a fraction of the already low amounts of heavy metals in urine.     

Protection of groundwater in relation to waste disposal in Wessex water authority

Wessex Water Authority, as one of the 10 water authorities of England and Wales, has the responsibility of liaising with Waste Disposal Authorities, that is the County Councils, to ensure that the water resources both groundwater and surface water are not polluted by waste disposal activities.The general policy adopted by Wessex in waste disposal liaison is to discourage waste disposal sites on aquifers. However, taking a realistic view on the subject and bearing in mind that a very large proportion of Wessex area is aquifer outcrop and the need to balance all interests, sites on aquifers are not ruled out automatically.All sites are looked at individually with all advantages and disadvantages being considered and if adequate reliable evidence can be provided to show that a site will not have a detrimental effect on a particular aquifer then the site would be accepted if the need was sufficiently great.This practical approach has been generally well accepted by all parties involved in Wessex and it has resulted in a wide variety of types of site and mechanisms employed to protect both surface water and groundwater.Three sites are described which represent very different circumstances. One is a large site in an isolated area of Carboniferous Limestone for which the proposed technique is to control groundwater levels around the site to ensure inflow to the top rather than outflow. The collected groundwater and leachate is then discharged to a sewer for treatment.A different approach used at a site on Forest Marble which is a fairly clayey material, which although used for small private supplies is not used for major public water supply sources to any significant degree, has been to line the site with a butyl rubber lining in order to contain the leachate and then dispose for treatment.The next approach considered is the acceptance of the dilute and disperse approach at an existing site on chalk; a limestone aquifer which is extremely permeable due to a profusion on inter connected fissures.Finally a proposed site at a non-aquifer site is described which avoids many of the problems encountered at sites situated on aquifers where groundwater has to be protected.The general conclusion reached is that waste disposal requires a flexible approach which results in a wide range of types of site. Such an approach can prevent many problems that can be caused by too rigid an approach.     

酒精废水深度处理回用设计探讨

结合工程实例，介绍了酒精废水改造工程“混凝沉淀＋过滤＋生物活性碳吸附＋清毒”的深度处理工艺，并对工程调试改造的运行效果进行了阐述，在酒精废水深度处理回用领域有较好的推广价值。     

Simulations of THM processes in buffer-rock barriers of high-level waste disposal in an argillaceous formation

The main objective of this paper is to investigate and analyse the thermo-hydro-mechanical (THM) coupling phenomena and their influences on the repository safety. In this paper, the high-level waste (HLW) disposal concept in drifts in clay formation with backfilled bentonite buffer is represented numerically using the CODE_BRIGHT developed by the Technical University of Catalonia in Barcelona. The parameters of clay and bentonite used in the simulation are determined by laboratory and in situ experiments. The calculation results are presented to show the hydro-mechanical (HM) processes during the operation phase and the THM processes in the after-closure phase. According to the simulation results, the most probable critical processes for the disposal project have been represented and analyzed. The work also provides an input for additional development regarding the design, assessment and validation of the HLW disposal concept.     

Rain water leachates of heavy metals in road surface sediments

Samples of street surface and roadside gutter sediments within a separately sewered catchment in N.W. London have been analysed for heavy metal contamination. Particle size distributions are presented and the removal efficiency of metal species demonstrated for various street cleaning procedures. Laboratory sorption and desorption studies are described and solution concentrations are obtained for Pb, Cd and Mn.Solubility curves are typically variable with time with Mn showing the strongest tendency to attain equilibrium. No obvious dependence of metal concentrations on grain size is readily apparent although Cd tends to desorb more rapidly from size fractions greater than 250 μm.     

煤矿酸性矿井水中重金属的来源及危害与处理

在分析AMD中重金属的主要来源及危害的基础上,对AMD中重金属的三种处理技术:物理化学法、生物法和人工湿地法分别进行了阐述,分析表明各种方法都具有一定的适用条件,其中微生物法是最有发展潜力的方法,也是以后的研究热点。     

Toxicity bioassay of heavy metals in water using Tetrahymena pyriformis

The toxicities of five heavy metal compounds on the survival of the ciliated protozoan Tetrahymena pyriformis were determined. Three-day old cultured cells were exposed to five concentrations of each test compound in one or more of three water series; distilled, soft, and hard water. A culture of each sample was placed in a plastic petri dish and covered with mineral oil to prevent evaporation. The cells were counted initially, then again at 0·5 h, 1 h, 2 h, 1 day, 2 days, 3 days, and on the fourth day. Lethal threshold concentrations and tolerance limit medians were determined by graphic methods. On a weight bases cadmium was most toxic, followed in decreasing toxicity by mercury, cobalt, zinc, and lead. Compared to similar fish data, all heavy metals were more toxic to T. pyriformis except lead. The toxicity of lead in soft versus hard water exemplified an antagonistic effect with greater than seven times the amount of lead necessary in hard water to produce comparable mortality as lead in soft water. On the other hand, the toxicity of mercury is about twice as great in hard water as in soft water (a synergistic effect). T. pyriformis appears to be a more sensitive indicator than fish of heavy metal contamination of water. T. pyriformis bioassay should prove a good means of determining the existence of many water pollutants.     

Human exposure to heavy metals in East Greenland II lead

The concentration of lead in 175 blood samples originating from the district of Angmagssalik, East Greenland and 130 from Aarhus, Denmark, has been determined. Both Greenland and Danish males had significantly higher (5%) blood lead than females (Eskimoan males 14.8 μg Pb/100 ml, females 12.8 μg Pb/100 ml; Danish males 10.5 μg Pb/100 ml, females 7.7 μg Pb/100 ml). For Danes living temporarily in Greenland the values were: males 10.5 and females 10.2 μg Pb/100 ml.Eskimos of both sexes were found to have higher blood lead values than Danes living in the same area. Danish males from Greenland and Denmark were not found to be different, whereas Danish women living in Greenland had a significantly higher (5%) mean value that women living in Denmark. In the Eskimo group, but not in the Danish, a weak, positive, but significant age correlation was found. 4 samples of Eskimo origin exceeded 35 μg Pb/100 ml accepted in the EEC as a maximum value for non-occupationally exposed persons. When re-examined 5 months later, all values were below this limit.The influence of eating habits (local or imported food) and smoking habits was tested, but not found to influence the blood lead concentration.The results have confirmed that blood lead levels in Greenland are comparable to those found in European industrialized areas. The reason for the unexpected high level in the arctic area with minimum car driving and industry remains to be clarified.     

Determination of heavy metals in natural water by the sorption-atomic-absorption method

The procedure for determining Hg, Cd, Pb, Zn, Cu elements in fresh water based on the preconcentration of these metals as complexes using poly-3-pyridyl-5-thioxo-4-allyl-4,5-dihydro-1H-1,2,3-triazole-1-carbodithionic acid with further measurement of atomic adsorption are proposed. The detection limits for metals are 5, 8, 20, 5 and 20 ng/dm³ respectively.     

铅锌尾矿重金属释放影响因素的探讨

铅锌尾矿废渣若不经过处理,会通过风蚀、径流对环境造成重金属污染,对尾矿废渣污染的研究一直是大家关注的方向。多年来,pH被证实是影响重金属释放的重要因素。本文通过实验,研究了浸提方法、pH和盐度对铅锌尾矿废渣重金属元素释放的影响。结果表明,Pb、Zn、Cd、As在pH值呈酸性和碱性时浸出率都较高,Cu、Ni则在pH值为碱性时浸出率更高,盐度对Pb的释放影响效果更为明显。     

天脊集团废水利用工程的建设

介绍了天脊集团废水利用工程概况，对水资源环境、工程控制范围进行了详细说明。经分析，工业废水处理后用于农业灌溉，提高了水的重复利用率，缓解了长治市资源紧张的现状。