The performance of a wetland system in treating lead (Pb)/zinc (Zn) mine drainage was evaluated by using the polyurethane
foam unit (PFU) microbial community (method), which has been adopted by China as a standardized procedure for monitoring water
quality. The wetland system consisted of four cells with three dominant plants: Typha latifolia, Phragmites australis and Paspalum distichum. Physicochemical characteristics [pH, EC, content of total suspended solid (TSS) and metals (Pb, Zn, Cd, and Cu)] and PFU
microbial community in water samples had been investigated from seven sampling sites. The results indicated that the concentrations
of Pb, Zn, Cd, Cu, and TSS in the mine drainage were gradually reduced from the inlet to the outlet of the wetland system
and 99%, 98%, 75%, 83%, and 68% of these metals and TSS respectively, had been reduced in concentration after the drainage
passed through the wetland system. A total of 105 protozoan species were identified, the number of protozoa species and the
diversity index (DI) gradually increased, while the heterotrophic index (HI) gradually decreased from the inlet to the outlet
of the wetland system. The results indicated that DI, HI, and total number species of protozoa could be used as biological
indicators indicating the improvement of water quality. 相似文献
The content of fine sand (< 200 μm) in primary sludge is relatively high in Chongqing sewage treatment plant owing to the part of rainwater will be mixed with sand and discharged into the municipal pipe network. Due to the insufficient separation of the sand, different obstacles to subsequent treatment processes may increase equipment wear, reduce effective volume of the tank, or shorten the cleaning cycle. There is a common use of grit chamber for the separation. Nevertheless, the use of hydrocyclone shows an outstanding performance in cost effectiveness and ease operation. The primary sludge in a sewage plant in Chongqing was monitored, and the average concentration of total suspend solids (TSS), total sand content, and volatile suspended solid (VSS) were 40.25 g/L, 17.51 g/L, and 13.41 g/L, respectively. The size of sand in the sludge was small, and the sand below 30 μm accounted for about 70% of the total sand. It formed flocs with organic matter and was removed in subsequent process units. While the size between 30–200 μm, called fine sand, was the main separation object, accounted for about 28.5%. According to XRF and XRD analysis, the sludge composition was mainly composed of quartz (SiO2), plagioclase (Na(AlSi3O8)), and calcite (CaCO3), which were similar to the main mineral composition of surface sediments and mountain rocks in the main urban area of Chongqing. A single-factor experiment on two types (FX100 and FX50) of hydrocylones was conducted to determine their abilities concerning the separation of fine sand and enrichment of organic matters from primary sludge. FX100 and FX50 showed best performance in the case of P = 0.17 Mpa, underflow diameter (Du) = 18 mm and P = 0.20 Mpa, Du = 6 mm, respectively. The removal efficiency of fine sand by hydrocyclone FX50 was 71.39%. While, it had poor performance on organic matter enrichment and the removal efficiency of which was 17.38%. By contrast, the removal rate by FX100 reached 61.89% for fine sand and only 6.89% for organic matters detached. The superimposition effect did not appear in the serial experiments on hydrocylone FX100 and FX50, but the power is 3.5 times of that of single-stage hydrocylone FX100. Comprehensive consideration of the processing capacity per unit time and operating power, the hydrocylone FX100 was more suitable for actual operation.
Environmental Science and Pollution Research - In recent years, with global climate change, the utilization of carbon dioxide as a resource has become an important goal of human society to achieve... 相似文献
Acid mine drainage (AMD) represents a major source of water pollution in the small watershed of Xingren coalfield in southwestern Guizhou Province. A detailed geochemical study was performed to investigate the origin, distribution, and migration of REEs by determining the concentrations of REEs and major solutes in AMD samples, concentrations of REEs in coal, bedrocks, and sediment samples, and modeling REEs aqueous species. The results highlighted that all water samples collected in the mining area are identified as low pH, high concentrations of Fe, Al, SO42? and distinctive As and REEs. The spatial distributions of REEs showed a peak in where it is nearby the location of discharging of AMD, and then decrease significantly with distance away from the mining areas. Lots of labile REEs have an origin of coal and bedrocks, whereas the acid produced by the oxidation of pyrite is a prerequisite to cause the dissolution of coal and bedrocks, and then promoting REEs release in AMD. The North American Shale Composite (NASC)-normalized REE patterns of coal and bedrocks are enriched in light REEs (LREEs) and middle REEs (MREEs) relative to heavy REEs (HREEs). Contrary to these solid samples, AMD samples showed slightly enrichment of MREEs compared with LREEs and HREEs. This behavior implied that REEs probably fractionate during acid leaching, dissolution of bedrocks, and subsequent transport, so that the MREEs is primarily enriched in AMD samples. Calculation of REEs inorganic species for AMD demonstrated that sulfate complexes (Ln(SO4)+and Ln(SO4)2?) predominate in these species, accounting for most of proportions for the total REEs species. The high concentrations of dissolved SO42? and low pH play a decisive role in controlling the presence of REEs in AMD, as these conditions are necessary for formation of stable REEs-sulfate complexes in current study. The migration and transportation of REEs in AMD are more likely constrained by adsorption and co-precipitation of Fe-Al hydroxides/hydroxysulfate. In addition, the MREEs is preferentially captured by poorly crystalline Fe-Al hydroxides/hydroxysulfate, which favors that sediments also preserve NASC-normalized patterns with MREEs enrichment in the stream.