Study on Relationship between Seasonal Temperatures and Municipal Wastewater Pollutant Concentration and Removal Rate

Abstract

In this study, the temperatures, pollutant concentrations and other indicators of municipal wastewater influent and effluent were tested for 7 months in 6 constructed wetland microcosms; the hydraulic retention time is 2 days. The results indicated that for both influent and effluent, there was a highly significant negative correlation (P<0.01) between the temperature and the pollutant concentrations, there was a significant difference (P<0.05) between seasonal temperatures, and the pollutant concentrations in summer and autumn were significantly different from those in winter (P<0.05). Furthermore, a regression analysis of pollutant concentration (y) based on changes in water temperature (x) in different seasons was performed. The analysis revealed that the relationship has the form ‘y = a -bx + cx2’, that under certain circumstances, pollutant concentrations can be calculated based on the temperature, and that the concentrations of NH4-N, Total Phosphorus (TP) and Soluble Reactive Phosphorus (SRP) had a significantly negative correlation with their removal rate (P < 0.01). However, seasonal temperature clearly did not have a direct impact on the pollutant concentration, and some studies have indicated that the different manners in which urban residents use water as the temperature changes may be the real reason that the pollutant concentrations of municipal wastewater vary with seasonal temperature. Furthermore, when designing and operating constructed wetlands, the impact of the changes in pollutant concentrations generated by seasonal temperature should be fully considered, dilution and other means should be taken to ensure purification.