2 Decades Constructed Wetland Experience in Treating Municipal Effluent for Power Plant Cooling at the Shand Power Station, SaskPower Part II: Annual Treatment Performance on BOD, TOC, NH3/NH4+, NO3-, pH and Alkalinity

Emmanuel K. Quagraine, Bruce Duncan, Minghui Chi, Austin Lothian



Within the power industry, there is a rejuvenated interest in exploiting treatment and other beneficial potentials of constructed wetlands (CWs) for power plant cooling. SaskPower has adopted such reuse application since 1994. This paper is second in series of publications on 20-year period experience at its Shand Power Station and highlights the yearly performance of the SaskPower CW on BOD, TOC, ammonia (NH3and/or NH4+), NO3-, pH and alkalinity. For first 2-years of operation, inflow to the CW was a facultative lagoon effluent, which was upgraded to conventional secondary treated quality. Ammonia and BOD removal efficiencies were fairly consistent throughout the study period; i.e. annual mean within 94-96% and ~58± 19% in the first 2 years and 74-92% and ~52± 25% for remaining 18-year period, respectively. On treating lagoon effluent, rise in pH occurred across the CW (0.14±0.16); depression (0.53±0.26) occurred upon switching to secondary effluent. NH3/NH4+ratio in the influent was implicated as a main regulator of pH changes across the CW. NO3-removal was ineffective on treating lagoon effluent, but improved to ~64 ± 36% on treating secondary effluent. The relative uptake of NO3- and NH4+ was found to generally depend on their proportions in the influent, but this relation failed when NO3- was over 14 times greater.