Impact of Waste Diversion on Water Quality in Lakes

Wastewater was diverted from three eutrophic lakes, given land treatment, and then discharged back to the lake tributaries. Results indicate loading reductions, some improvements in water quality but no changes in trophic status because the untreated nutrient sources remained high. The land treatment facility resulted in significant reductions in nutrient loadings to the lakes but the effectiveness of these reductions was limited because of other untreated nutrient sources. Nevertheless short-term improvements in lake phosphorus, nitrogen, chlorophyll a and hypolimnetic oxygen were observed in the three lakes but each lake remained eutrophic because background loadings were still very high. No improvements in water transparency were observed because secchi disc is relatively insensitive to moderate changes in chlorophyll a at high levels. The study results indicate that wastewater diversion can be effective in reducing nutrient loads and concentrations but will not necessarily reverse lake eutrophication.