Biofilm formation and microbial community analysis of the simulated river bioreactor for contaminated source water remediation

Background, aim, and scope

The start-up pattern of biofilm remediation system affects the biofilm characteristics and operating performances. The objective of this study was to evaluate the performances of the contaminated source water remediation systems with different start-up patterns in view of the pollutants removal performances and microbial community succession.

Methods

The operating performances of four lab-scale simulated river biofilm reactors were examined which employed different start-up methods (natural enrichment and artificial enhancement viadischarging sediment with influent velocity gradient increase) and different bio-fillers (Elastic filler and AquaMats? ecobase). At the same time, the microbial communities of the bioreactors in different phases were analyzed by polymerase chain reaction, denaturing gradient gel electrophoresis, and sequencing.

Results and discussion

The pollutants removal performances became stable in the four reactors after 2 months?? operation, with ammonia nitrogen and permanganate index (COD_Mn) removal efficiencies of 84.41?C94.21% and 69.66?C76.60%, respectively. The biomass of mature biofilm was higher in the bioreactors by artificial enhancement than that by natural enrichment. Microbial community analysis indicated that elastic filler could enrich mature biofilm faster than AquaMats?. The heterotrophic bacteria diversity of biofilm decreased by artificial enhancement, which favored the ammonia-oxidizing bacteria (AOB) developing on the bio-fillers. Furthermore, Nitrosomonas- and Nitrosospira-like AOB coexisted in the biofilm, and Pseudomonas sp., Sphaerotilus sp., Janthinobacterium sp., Corynebacterium aurimucosum were dominant in the oligotrophic niche.

Conclusion

Artificial enhancement via the combination of sediment discharging and influent velocity gradient increasing could enhance the biofilm formation and autotrophic AOB enrichment in oligotrophic niche.     

Can body-size patterns of ciliated zooplankton be used for assessing marine water quality? A case study on bioassessment in Jiaozhou Bay, northern Yellow Sea

Introduction

In order to reveal the potential relationships between body-size patterns of microzooplankton and environmental status, the spatial patterns in body-size spectra of ciliated zooplanktons were studied based on an annual dataset in a bay of the Yellow Sea, northern China.

Materials and methods

A total of 120 samples were collected at a depth of 1?m from each of five sampling sites with a spatial gradient of environmental stress from June 2007 to May 2008. A range of physico-chemical variables were measured synchronously for comparison with biotic parameters.

Results

The spatial body-size patterns of ciliated zooplankton represented significant differences among the five sites, and were significantly correlated with the changes of physico-chemical parameters, especially salinity, dissolved oxygen and nutrients. Two paired indices, the average body-size distinctness (AvBSD) and the variation in body-size distinctness (VarBSD), were proposed based on the trait resemblances among ciliate species in body-size pattern. The paired measures showed a clear decreasing trend of departure from the expected body-size spectra in response to water quality status.

Conclusion

These results suggest that the body-size pattern of ciliated zooplankton might be used as a potential indicator of marine water quality.     

利用MCMP微生物制剂减少剩余污泥产量的研究

通过在3组日处理规模为5 m³/d的活性污泥法装置中进行连续进出水试验，考察了投加多功能复合微生物制剂（multifunctional compound micro-organisms preparation ，MCMP）对污水处理过程中剩余污泥减量的影响。中试研究结果表明，曝气池中，每次MCMP菌剂加入量为日处理水量的0.02%～0.04%的条件下，运行2个月装置未排放剩余污泥，有效地实现剩余污泥源头减量的预期要求。该技术不增加或改变原有污水处理工艺和运行方式，不增加处理系统总的动力消耗，并且不会对出水水质产生不良影响。     

Catalytic activity of Ru/Al2O3 for ozonation of dimethyl phthalate in aqueous solution

With dimethyl phthalate as the model pollutant and Ru/Al(2)O(3) as catalyst, this paper systemically investigates the removal of total organic carbon (TOC) of system. Our results have confirmed that Ru/Al(2)O(3) can significantly increase the effect of ozonation. TOC removal in 120 min can reach 72% while only 24% with ozone alone. The optimal catalyst preparing condition was 0.1 wt% Ru content, 600 degrees C calcination temperature, 0.5-1.0mm particle diameter, which is characterized by a high surface area and a large population of surface active sites. The contrasting experiments of ozone alone, catalyst adsorption after ozonation, and catalytic ozonation confirmed that catalytic reaction was the most important process to TOC removal in system with Ru/Al(2)O(3) as catalyst.     

The ageing effect on the bioaccessibility and fractionation of arsenic in soils from China

Ingestion of contaminated soil has been recognized as an important exposure pathway of arsenic for humans, especially for children through outdoor hand-to-mouth activities. An improved sequential extraction procedure was employed in an attempt to reveal the relationship between bioaccessibility and fractionation of As in five soils from China. Arsenic bioaccessibility in acidic ( approximately pH 4.5) soils reached approximately stable levels after a sharp decline within one week of ageing. In contrast, As bioaccessibility in higher pH (>6.0) soils was found to be significantly higher and took two weeks of ageing to reach stable levels. The artificially added As was more labile than indigenous As. The main proportions of added As were found in the specifically sorbed and amorphous and poorly-crystalline hydrous Fe/Al oxide-bound fractions. Correlation analysis shows that the non-specifically and specifically sorbed As are likely to constitute the main proportion of bioaccessible soil As. The soil content of amorphous and crystalline Fe/Al oxides and soil pH appear to be the key factors controlling, not only the time needed to reach a steady state, but also the magnitude of the bioaccessibility of As added to the soils.     

Efficiency of surfactant-enhanced desorption for contaminated soils depending on the component characteristics of soil-surfactant--PAHs system

The sorption of surfactants onto soils has a significant effect on the performance of surfactant enhanced desorption. In this study, the efficiency of surfactants in enhancing desorption for polycyclic aromatic hydrocarbons (PAHs) contaminated soils relative to water was evaluated with a term of relative efficiency coefficient (REC). Since the sorption of surfactants onto soils, surfactants only enhanced PAH desorption when REC values were larger than 1 and the added surfactant concentration was greater than the corresponding critical enhance desorption concentration (CEDC), which was defined as the corresponding surfactant concentration with REC=1. A model was utilized to describe and predict the REC and CEDC values for PAH desorption. The model and experimental results indicated that the efficiency of surfactants in enhancing PAH desorption showed strong dependence on the soil composition, surfactant structure and PAH properties. These results are of practical interest for the selection of surfactant to optimize soil remediation technologies.     

The impact of sewage irrigation on the uptake of mercury in corn plants (Zea mays) from suburban Beijing

The impact of sewage irrigation on the uptake and translocation of mercury (Hg) in corn plants (Zea mays) was investigated. Corn plants were harvested the same day from two nearby fields in suburban Beijing, one irrigated historically with sewage effluent, and one irrigated solely with groundwater. Hg content was analyzed in the soil, roots and stems, while percent moisture and soil organic content were analyzed in the soil samples. The concentration of Hg in the soil and roots, and the soil organic content were not significantly different between the two fields, despite the historic practice of sewage irrigation. Hg content in roots was positively correlated with soil Hg concentration (r=0.95, n=6). The transfer coefficients between roots and stems were significantly higher in the control site (control: 2.06, sewage-irrigated: 0.44, p<0.05), indicating that the barrier effect of the roots was not consistent between the two fields.     

The study of distribution and fate of nitrobenzene in a water/sediment microcosm

In November 2005, an explosion occurred at a petrochemical plant of the Jilin Petrochemical Corporation in Jilin Province, China. A nearby water body was seriously polluted with a large spill of toxic substances made up of a mixture of benzene, aniline, and nitrobenzene (NB). To understand the long term impact of NB on public health and ecosystem around the Songhua River, it was necessary to investigate its fate in the environment. In this study, a microcosm was used to mimic the polluted water system and to study the transport and fate of NB in the river water body. The volatility and biodegradation of NB was investigated and a Markov model was applied to predict the fate of NB in the environment. The simulated results matched very well with the results obtained from the microcosm experiment. The model indicated that at room temperature and after around 500 h, there was only residual NB in the water and sediment. Most of the NB (around 82%) evaporated into the air and 18% was degraded by microorganisms.     

Well water contaminated by acidic mine water from the Dabaoshan Mine, south China: chemistry and toxicity

An investigation into well water quality was carried out in a rural area subject to irrigation with acidic mine water from the Guangdong Dabaoshan Mine, southern China. The results of water pH measurements from 112 wells in two different seasons suggest that the well water has been contaminated to varying degrees in the investigated Shangba floodplain (approximately 11km south of the Guangdong Dabaoshan Mine). There is a trend that well water pH increased southwards, suggesting that the impacts of acidic irrigation water on groundwater decreased with increasing distance to the entry point of acidic irrigation water. Water quality monitoring results of the selected wells show that Cu and Cd in the water exceeded the limits set in the Chinese National Standards for Drinking Water (GB 5749-85) for the wells close to the irrigation water source. If the World Health Organization (WHO) standard was considered, Cd in some wells was almost 10 times as high as the WHO guideline value (0.003mg l(-1)). Water collected from the location closest to the acidic irrigation water source was acutely toxic to the test organism (Daphnia carinata) even after 51 time dilution. It is likely that the extremely high mortality rate of the local population reported for the study area is at least partly related to the high levels of heavy metals, particularly Cd in the drinking well water.