Analysis and evaluation of the treatment and reuse of tailwater: A case study in Erhai Lake

The utilization of reclaimed water is an important way to solve the shortage of water resources. Here, an analysis and evaluation of the tailwater treatment and reuse from 6 wastewater treatment plants (WWTPs) located in suburb surrounding the Erhai Lake after the completion of representative project on sewage interception and pollution control was conducted. All tailwater was deeply treated by wetland and pond, which was used for agricultural irrigation, greening landscape and ecological supplement water of water-scarce rivers. The reclaimed water used inside and outside the Erhai Basin is 25432.3 m3/d and 18181.1 m3/d which accounts for 58.3% and 41.7% of the total tailwater, respectively. The implementation of the project has remarkably diminished pollution loads before it enters the Erhai Lake, and about 83.3% of chemical oxygen demand (COD), 90.8% of total nitrogen (TN), and 78.8% of total phosphorus (TP) loads has been reduced. Based on the analysis, the characteristic index system including 13 indicators was constructed from three aspects of environmental benefit, social-economic benefit and consumption-resource benefit and the analytic hierarchy process (AHP) was applied to determine the weight. According to the above evaluation results, it can conclude that the environmental benefit, social-economic benefit and consumption-resource benefit of the reclaimed water reuse project are significant. Especially for social-economic benefit, the three indicators all belonged to the first and second class. It suggested that the ecological purification and reclaimed water use project has effectively reduced the nitrogen and phosphorus pollutants, and alleviate the problem of water shortage in the water-scarce plateau area. The results of the paper are expected to provide a scientific basis and practical engineering guidance for the deep treatment and resource utilization of tailwater. [Display omitted] •The treatment and reuse of tailwater from WWTPs around Erhai Lake were analyzed.•All tailwater was deeply treated by wetland and pond.•58.3% and 41.7% of reclaimed water was used inside and outside basin, respectively.•Reclaimed water was used for irrigation, greening and ecological supplement.•Benefit about environment, social-economy, consumption-resource was evaluated.