Abstract
ABSTRACTSewage treatment plant (STP) effluent has been used as ecological supplementary water in dry and polluted urban rivers. However, more consideration should be given to the impact of STP effluent on water quality and the environment. In this paper, a typical urban tributary river of Dianchi was selected to study the impact of STP effluent on water quality and plankton communities. Using a paired-sample t-test, factor analysis and canonical correspondence analysis, changes in water quality, plankton communities and their relationships were analyzed. The results showed that STP effluent decreased the concentrations of suspended solid, chemical oxygen demand, five-day biological oxygen demand (BOD5) and total phosphorus. However, it significantly increased the concentration of nitrate, total nitrogen and nitrate nitrogen (NO3-N). A distinct shift in the phytoplankton community from Chlorophyta (green algae) to Bacillariophyta (diatoms) occurred after the influx of STP effluent and further analysis indicated that this shift was primarily caused by the increase in NO3-N and facilitated by the seasonal rise in water temperature. Zooplankton communities were less sensitive to changes in water pollution condition than phytoplankton communities and the zooplankton community structure of the Chuanfang River was mainly influenced by water temperature.
Highlights
Dianchi Lake (2451 0N, 10242 0E) is a well-known shallow plateau lake located in Kunming, Yunnan province in the south-west of China
The subtropical monsoon climate prevails in the Dianchi Lake basin, and the Water temperature (WT) of the Chuanfang River, which ranged from 8 C in December 2013 to 22.7 C in July 2014 during the monitoring period, was consistent with the features of the local climate (Huang et al 2014; Wu et al 2014)
The recharge of Sewage treatment plant (STP) effluent is beneficial to the mitigation of water pollution in the Chuanfang River caused by the inflow of sewage, especially when the nitrification process of the STP works properly
Summary
Dianchi Lake (2451 0N, 10242 0E) is a well-known shallow plateau lake located in Kunming, Yunnan province in the south-west of China. With the rapid expansion of urban land use and the lack of sewage treatment systems, large amounts of sanitary sewage were carried into Dianchi Lake via the inflowing rivers. This process caused eutrophication and a rapid deterioration in water quality in Dianchi Lake (Huang et al 2014; Li et al 2014). To reduce the pollution in Dianchi Lake, the Kunming city government has invested tens of billions of Chinese Yuan to promote six types of pollution control projects in the Dianchi Lake basin: (1) a lakeside sewage interception and transportation system construction project, (2) a water diversion and water conservation project, (3) an inflowing river regulation project, (4) an agricultural and rural non-point source management project, (5) an ecological restoration and construction project and (6) an ecological dredging project. Dianchi Lake received an average of 72%, 78% and 80% of its chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN), respectively, from 35 major inflowing rivers (KEPB 2011)
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