Jingmei Sun

A case study of an enhanced eutrophication model with stoichiometric zooplankton growth sub-model calibrated by Bayesian method

Urban lakes in China have suffered from severe eutrophication over the past several years, particularly those with relatively small areas and closed watersheds. Many efforts have been made to improve the understanding of eutrophication physiology with advanced mathematical models. However, several eutrophication models ignore zooplankton behavior and treat zooplankton as particles, which lead to the systematic errors. In this study, an eutrophication model was enhanced with a stoichiometric zooplankton growth sub-model that simulated the zooplankton predation process and the interplay among nitrogen, phosphorus, and oxygen cycles. A case study in which the Bayesian method was used to calibrate the enhanced eutrophication model parameters and to calculate the model simulation results was carried out in an urban lake in Tianjin, China. Finally, a water quality assessment was also conducted for eutrophication management. Our result suggests that (1) integration of the Bayesian method and the enhanced eutrophication model with a zooplankton feeding behavior sub-model can effectively depict the change in water quality and (2) the nutrients resulting from rainwater runoff laid the foundation for phytoplankton bloom.

Utilization of brewery wastewater for culturing yeast cells for use in river water remediation.

Successful in situ bio-augmentation of contaminated river water involves reducing the cost of the bio-agent. In this study, brewery wastewater was used to culture yeast cells for degrading the CODCr from a contaminated river. The results showed that 15 g/L of yeast cells could be achieved after being cultured in the autoclaved brewery wastewater with 5 mL/L of saccharified starch and 9 g/L of corn steep liquor. The CODCr removal efficiency was increased from 22% to 33% when the cells were cultured using the mentioned method. Based on the market price of materials used in this method, the cost of the medium for remediating 1 m3 of river water was 0.0076 US dollars. If the additional cost of field implementation is included, the total cost is less than 0.016 US dollars for treating 1 m3 of river water. The final cost was dependent on the size of remediation: the larger the scale, the lower the cost. By this method, the nutrient in the brewery wastewater was reused, the cost of brewery wastewater treatment was saved and the cost of the remediation using bio-augmentation was reduced. Hence, it is suggested that using brewery wastewater to culture a bio-agent for bio-augmentation is a cost-effective method.

Investigation of Local Plants along Dagu Sewage River for Phytoremediation of Sediments

The study was aimed at investigating the local plants along two sides of Dagu River to achieve guidance on the harness, remediation or management of Dagu River. For this, the herbage plant species and their covering area, heavy metal contents in the plants, and the correlation analysis between metals in local plants and in nearby sediments were investigated. Results indicate that the dominant plants in the heavily polluted sections of Dagu River are mainly Humulus scandens, Polygoum orientale and Common reed. These three herbage plants are effective in phytoremediation of multi-metal contaminated sediments. Different planting or interplant can remediate multi-metal polluted sediments or be selected to cover the landfill sites of multi-metal polluted dredge-sediments. The results of this study may guide the current harness and remediation of Dagu River sediments and future scientific management of Dagu River.

Determination of Optimal Sampling Transects for Heavy Metal Contaminated Dagu River Sediments

Determination of optimal sampling transects and pollutants for river sediments are essential and valuable. To determine if the concentration of some metals were highly correlated, correlations between heavy metals (As, Pb, Cd, Cr, Hg, Cu, Ni and Zn) were analyzed using statistic analysis software (SAS) based on monitoring data of heavy metals along the whole watercourse sediments of Dagu River. To allow a reduction in the number of monitoring transects analyzed in the future monitoring of watercourse, a co-threshold method was developed based on correlations between metals and corrected with the first three extremum single thresholds. Results show that all investigated metals except Zn and Ni in Dagu River sediments are positively correlated with at least other three metals. Among the monitored 28 sampling transects, 11 sampling transects are found to be the more informative sampling transects. To determine the metal contents in Dagu River sediments in the future, only the detection of the preferred metals in each informative sampling transect are required.

THMs in Re-Chlorinated Drinking Water

The concentration of trihalomethanes (THMs) could increase significantly in post-chlorinated water especially as water is boiled. This study aimed to investigate the levels of THMs and residual chlorine in the existing water distribution system, and to evaluate the possibility of additional THMs formation in distribution system for drinking water and re- chlorinated drinking water in roof water tank. The investigation results showed that the level of residual chlorine in main pipelines generally lies between 0.5 and 1.2 mg l -1 , decreasing to less than 0.4 mg l -1 or even close to zero (not detectable) at the end of pipelines. The level of total THMs in both main pipelines and the end of pipelines was found to lie between 11.4 and 16.3 mug l -1 . However, a significant increase in THMs level was observed in post-chlorinated water, especially when water is heated.