Analysis of radon concentration in drinking water in Baoji (China) and the associated health effects

This paper presents the results of radon concentration measurements in drinking water from the municipal water supply system and private wells located in Baoji, China. The measurements were carried out on 69 samples. The mean values of tap water and well water were found to be 12 kBq m(-3) with a maximum of 18 kBq m(-3) and 41 kBq m(-3) with a maximum of 127 kBq m(-3), respectively. The well water samples obtained from different depth-well (water-bearing levels), i.e. shallow well (well depth under 10 m) water, middle well (well depth 10-30 m) water and deep well water, have respective mean values of 24, 34 and 56 kBq m(-3). The contributions of the observed radon concentration in drinking water to indoor radon account for 2.8-13.2% of the mean value of Shaanxi indoor radon concentration and the effective dose to the dweller owing to inhalation of radon emanating from household water is 0.03-0.14 mSv y(-1).     

Measurement of radon concentration in water using the portable radon survey meter

A measurement method for measuring radon in water using the portable radon survey meter (RnSM) was developed. The container with propeller was used to stir the water samples and release radon from the water into the air in a sample box of the RnSM. In this method, the measurement of error would be <20 %, when the radon concentration in the mineral water was >20 Bq l(-1).     

Removal of trihalomethanes from drinking water by nanofiltration membranes

Chlorine reacts with the natural organic matter (NOM) in waters and forms disinfection by-products (DBP). Major of these by-products are trihalomethanes (THM) and haloacetic acids (HAA). They have been known to cause cancer and other toxic effects to human beings. This study determined the removal efficiencies of THM by nanofiltration (NF) techniques with NF200 and DS5 membrane. The rejection of this chlorination by-products was studied at various feed concentration by changing transmembrane pressure. Experimental results indicated that in general increasing operating pressure produces a higher flux but does not have a significant effect on THM rejection. On the other hand, increasing the feed concentration produces a little change in the overall flux and rejection capacity. NF200 membrane removed more THM than DS5 membrane. The higher removal efficiency of dibromochloromethane (DBCM) was attributed to brominating characteristics (higher molecular weight (MW) and molecular size). As a consequence, the results of this study suggest that the NF membrane process is one of the best available technologies for removing THM compounds.     

The NitRem process for nitrate removal from drinking water

A. F. Miquel of Otto Oeko-Tech looks at potential water treatment technologies that are able to remove nitrates from drinking water and details the way in which the development of nitrate selective membranes has resulted in the adaptation of electrodialysis and the development of the Nitrem process.     

Ammonia and iron removal from drinking water with clinoptilolite tuff

Field experiments were carried out for removal of ammonium and iron ions from drinking water containing high amounts of humic acids and dissolved gases. Three ion exchange columns filled with sodium form clinoptilolite (particle size: 0.5–1.0 mm), were connected in series. The ammonia content of the influent drinking water was ∼10 mg dm⁻³ and the 0.5 mg NH₃-N/dm³ breakthrough concentration was kept. The iron content ranged between 0.70–0.90 mg dm⁻³ and 0.05 mg Fe/dm³ was chosen as a limit for good quality drinking water. In a 90 h continuous experiment about 3.24 m³ drinking water was purified by three 4 dm³ bed volume, 9.5 cm ID × 92 cm ion exchange columns. The ammonia ion exchange capacity was about 3 mg NH₃-N/g zeolite. The natural zeolite contained only 46% clinoptilolite. For regeneration, 50 dm³ (12.5 BV) regenerant was used. After backwashing with 10 BV ammonia-free water, the freshly regenerated column was placed to the end of the series in service. Design and construction of a pilot-plant unit, including a 50 m³/day capacity ion-exchange system, is suggested.     

Chlorination byproducts, their toxicodynamics and removal from drinking water

No doubt that chlorination has been successfully used for the control of water borne infections diseases for more than a century. However identification of chlorination byproducts (CBPs) and incidences of potential health hazards created a major issue on the balancing of the toxicodynamics of the chemical species and risk from pathogenic microbes in the supply of drinking water. There have been epidemiological evidences of close relationship between its exposure and adverse outcomes particularly the cancers of vital organs in human beings. Halogenated trihalomethanes (THMs) and haloacetic acids (HAAs) are two major classes of disinfection byproducts (DBPs) commonly found in waters disinfected with chlorine. The total concentration of trihalomethanes and the formation of individual THM species in chlorinated water strongly depend on the composition of the raw water, on operational parameters and on the occurrence of residual chlorine in the distribution system. Attempts have been made to develop predictive models to establish the production and kinetics of THM formations. These models may be useful for operational purposes during water treatment and water quality management. It is also suggested to explore some biomarkers for determination of DBP production. Various methods have been suggested which include adsorption on activated carbons, coagulation with polymer, alum, lime or iron, sulfates, ion exchange and membrane process for the removal of DBPs. Thus in order to reduce the public health risk from these toxic compounds regulation must be inforced for the implementation of guideline values to lower the allowable concentrations or exposure.     

饮用水处理用活性炭废炭的粉磨能耗

利用水厂活性炭废炭和行星式球磨机分别进行废炭干、湿法粉磨实验,激光粒径仪测定粉磨产物的粒径d_(50)值,在罗辛-拉姆勒粒径特性方程基础上研究干、湿法粉磨方式和磨机转速对产物d_(50)值和能耗的影响,建立废炭粉磨能耗模型,并用实际能耗值对模型进行验证。结果表明,干、湿法粉磨条件下,随能耗增加,产物d_(50)值和粒径模数均先减小后趋于平缓;在200~300 r/min转速范围内,浆料质量比为40%的湿法粉磨较干法粉磨易获得更小d_(50)值、比能耗更低、粒径分布范围更窄的粉磨产物;粉磨方式、磨机转速均影响废炭粉磨能耗;以罗辛-拉姆勒粒径特性方程为基础的能耗方程适用于行星式球磨机粉磨废炭过程。     

Combined electrocoagulation and electroflotation for removal of fluoride from drinking water

A combined electrocoagulation (EC) and electroflotation (EF) process was proposed to remove fluoride from drinking water. Its efficacy was investigated under different conditions. Experimental results showed that the combined process could remove fluoride effectively. The total hydraulic retention time required was only 30 min. After treatment, the fluoride concentration was reduced from initial 4.0-6.0mg/L to lower than 1.0mg/L. The influent pH value was found to be a very important variable that affected fluoride removal significantly. The optimal influent pH range is 6.0-7.0 at which not only can effective defluoridation be achieved, but also no pH readjustment is needed after treatment. In addition, it was found that SO(4)(2-) had negative effect; Ca(2+) had positive effect; while Cl(-) had little effect on the fluoride removal. The EC charge loading, EF charge loading and energy consumption were 3.0 Faradays/m(3), 1.5 Faradays/m(3), and 1.2 kWh/m(3), respectively, under typical conditions where fluoride was reduced from initial 4.0 to 0.87 mg/L.     

膜混凝反应器除砷

用国产中空纤维膜组件,研究膜混凝反应器小试规模条件下的除砷效果.结果表明:膜混凝反应器的除砷效果良好,砷的去除率高达92.8%～98.2%,可使原水中As(V)的浓度从100 μg/L左右降至10μg/L以下,出水平均舍砷4.40μg/L,完全满足城市供水水质标准的要求;膜污染是导致膜比通量下降的主要原因,铁盐对膜污染的贡献较小,膜污染主要是有机物污染,占总量的67.2%;通过物理清洗和化学清洗可使膜比通量恢复到新膜的87.8%.     

Review of strategies for minimizing bromate formation resulting from drinking water ozonation

Ozonation is a more attractive disinfection method than chlorine in that it can meet the current USEPA regulations. Indeed, ozone and its primary reactive products, the hydroxyl free radical (OH^·) especially, are strong oxidizing agents, capable of substantial oxidation. However, ozonation can also lead to the formation of potentially harmful by-products, which can be dealt with either by removing the disinfection by-products themselves or by inhibiting their formation via precursor removal methods and process optimization techniques. This paper provides a review of ozonation and by-product formation chemistry, effective approaches toward the control of bromate formation, and bromate precursor removal technologies.     

Factors influencing lead and iron release from some Egyptian drinking water pipes

The major objective of this study is to assess the effect of stagnation time, pipe age, pipes material and water quality parameters such as pH, alkalinity and chloride to sulfate mass ratio on lead and iron release from different types of water pipes used in Egypt namely polyvinyl chloride (PVC), polypropylene (PP) and galvanized iron (GI), by using fill and dump method.Low pH increased lead and iron release from pipes. Lead and iron release decreased as pH and alkalinity increased. Lead and iron release increased with increasing chloride to sulfate mass ratio in all pipes.EDTA was used as an example of natural organic matter which may be influence metals release. It is found that lead and iron release increased then this release decreased with time.In general, GI pipes showed to be the most effected by water quality parameters tested and the highest iron release. PVC pipes are the most lead releasing pipes while PP pipes are the least releasing.