Wastewater Treatment and Reuse on Campus: A Case Study in Kun Shan University

摘要

Because of water shortage, water treatment and reuse have become crucial. In this study, on the campus of Kun Shan University, an ecological channel with a treatment capacity of 150 CMD and a hydraulic retention time of 46.6 hr was used for the purification of reclaimed water. Different aquatic plants were grown to purify the used water, including floating aquatic plants such as water lettuce (Pistia stratiotes L.), Salvinia (Salvinia molesta D.S. Mitch.), and water hyacinth (Eichhornia crassipes (Mart.) Solms); submerged aquatic plants such as hornwort (Ceratophyllum demersum L.); and emergent plants such as Hygrophila pogonocalyx Hayata and H. salicifolia (Vahl) Nees. In water quality monitoring programs, dissolved oxygen, chemical oxygen demand, suspended solids, total nitrogen, total phosphate, and turbidity were measured weekly. The system was in operation from March 2015 to April 2017, across a total of nine seasons. The results obtained in this study indicated significant improvement in water quality, and dissolved oxygen in water increased from 1.6 mg/L to 5.3 mg/L. After treatment, performance for chemical oxygen demand, suspended solid, turbidity, total nitrogen, and total phosphate removal was 44.0%, 81.2%, 80.1%, 41.6%, and 18.0%, respectively. The results also revealed that Salvinia made little contribution to nitrogen removal, whereas Da-Ann hygrophila, willowleaf hygrophila, and hornwort exhibited great potential for nitrogen removal. Additionally, hornwort demonstrated great potential for phosphorus removal. The purified water is currently used for environmental maintenance and for supplying the landscape pool; moreover, the water purification process reduces the consumption of tap water and improves the efficiency of water utilization.