Effects Of Cadmium And Lead On Performance Of SBR In Treating Sewage

To improve water quality and make water environment safe in small towns, biological wastewater treatment is one of the most effective way. The objective of biological wastewater treatment was to improve processing efficiency, lessen disposal cost and make running harmoniously. Among the influential factors, poisons such as heavy metals were not studied enough. On the other hand, SBR (Sequencing Batch Reactor) was much adapTab. to small towns, which had its own characteristics in wastewater treatment. Because of the weak economic condition of towns, unsound drainage system, it became one of the essential matters of the biological treatment that alleviating the effects of extraneous poisons.With a view to actual demand, in the experiment, employing SBR to treat small towns' wastewater was coupled with heavy metals intimidation and then the effects of cadmium and lead on running of SBR system were studied. Due to the difference of the objective in towns when treating wastewater, two operating modes in SBR were designed, that is, COD removal technique of SBR and nitrogen & phosphorous removal technique of SBR. The research could richen the contents of water processing engineering toxicology theoretically and could provide scientific foundation for deep wastewater treatment in small towns practically.According to the components of typical domestic sewage and effluent standard, analytical reagents (A.R.) simulated wastewater. We ourselves designed four sets of reactors in parallel connection and inoculated activated sludge from aeration basin of a sewage treatment plant to the reactors. The sludge was domesticated and cultivated until the sludge performance was good enough to ensure SBR system operating stably.Firstly, the two normal operating conditions of SBR for two different targets were determined. To remove COD, the operating period was designed three groups, that is, 240min, 360min and 480min. In each group, the percentages of fill, aeration, settle, decant and idle to the whole period were 25%, 35%, 20%, 15% and 5%, respectively. The four modes of fill were designed as aeration after fill, aeration while fill then stirring while aeration, stirring while fill then stirring while aeration, stirring and aeration while fill. Considering operating efficiency and cost comprehensively, the normal operating condition to remove COD (NOCRCOD) was determined as period 240min, stirring while fill 60min, aeration 84min, settle 48min, decant 36min, idle 12min. To remove nutrients, the normal one (NOCRN/P) was determined as period 600min, stirring while fill 60min, aeration 270min, stirring 120min, settle 120min, decant 30min.To ensure that oxygen provided in SBR was in normal level, the content of DO in SBR was...