The results showed that the average removal rates of five-day biological oxygen demand, total suspended solids and NH4+-N were 33.6% (between -6.7% and 82.1%), 56.3% (between -83.0% and 93.4%) and 10.7% (between -13.0% and 83.3%), respectively. The influent and effluent water samples were taken periodically for the analyses of pH, temperature, dissolved oxygen, total suspended solids, five-day biological oxygen demand, NH4+-N. The objective of this study was to evaluate the treatment efficiency of a gravel contact oxidation treatment system which was newly constructed under the riverbed of Nan-men Stream located at the Shin Chu City of Taiwan.

Information obtained from this study is helpful in providing a design basis for similar wetland systems to control agricultural non-point source pollution. The nitrogen analysis results showed that ammonia nitrogen and nitrate nitrogen were the main nitrogen species present in the influent and effluent of each wetland functioning unit. Therefore, the pollutant removal efficiency could not be determined. There was no flow in the wetland during the winter. There was a little seasonal change on the COD, SS, TN, and TP removal efficiency.

Results showed that the wetland systems removed various pollutants. In addition, influent and effluent samples of each riparian wetland treatment unit were collected and analyzed for nitrogen (nitrate, nitrite, ammonia, and organic nitrogen) and phosphorus (organic phosphorus and phosphate). The influent and effluent mass loadings of total nitrogen (TN), total phosphorus (TP), suspended solid (SS), and chemical oxygen demand (COD) of riparian wetland systems were monitored for nearly one year.

To control eutrophication caused by agricultural non-point sources, integrated riparian wetlands were constructed and operated to intercept and treat the polluted water flowing into the Fuxian Lake. From the results it was showed that when aeration 6 hours, stirring 4 hours and settling 2 hours in SBR, the removal rates of COD, nitrogen and phosphorus of domestic sewage were 93%, 98% and 83%, respectively when aeration 5 hours, stirring 5 hours and settling 1 hour in the SBR, the removal rates of COD and nitrogen of pharmaceutical wastewater were 83% and 90%, respectively when aeration 4 hours, stirring 4 hours and settling 1 hour in the SBR, removal rates of COD, nitrogen and phosphorus of industrial wastewater were 97%, 93% and 97%, respectively. The effects of different conditions of aeration, stirring and settling on the efficiency of pollutants removal were explored to optimize the performance, especially for the removal of organic matter (COD), ammonia nitrogen(NH4⁺-N), total nitrogen(TN) and total phosphorus(TP) of different types of polluted water. A laboratory-scale SBR was used to treat sewage, medical wastewater and industrial wastewater. The objective of this study was to investigate the pollutant removal efficiency of different types of wastewaters by a sequencing batch reactor (SBR). Therefore, it is important to effectively control aeration in the front zone of the gravel contact oxidation treatment system to improve the removal efficiency of total nitrogen. It was only a migration process among different forms of nitrogen. Although the concentration of NH3-N decreased quickly, nitrogen was not removed by microbial degradation.

However, microbial denitrification was not effective due to high concentrations of dissolved oxygen in non-aeration zones of the gravel contact oxidation treatment system. Therefore, the gravel contact oxidation system is quite effective in pollution control for combined sewage and rainwater. Results showed that removal rates of BOD, SS and NH3-N ranged 85–95% (averaged 90%), 70–95% (averaged 85%), and 70–90% (averaged 80%), respectively. In this study, influent and effluent were sampled monthly for the analyses of dissolved oxygen (DO), suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia nitrogen and nitrate. The Guiyang gravel contact oxidation treatment system was constructed to purify combined sewage and rainwater in Taipei.

The gravel institute