Removal of Phosphorus and Other Components from Eutrophic Lake Water

摘要

Increasing phosphorus (P) content and decreasing water quality of shallow Lake Caron, 75 km north of Montreal, Canada has led to the implementation of many management strategies to restore the lake. Despite the perceptible reduction in external sources, except drainage from nearby forest areas, the P level in lake water still remain high and constitute a major challenge to the lake restorers. As part of the restoration plan, a laboratory study was performed to assess the effectiveness of non-woven geotextiles in reducing the nutrients (P and nitrogen, N) concentrations and improving the lake water quality. Two geotextile filters (TE-GTN350 and TE-GTX400) with different apparent opening sizes and materials were tested in three different combinations: (ⅰ) TE-GTN350/TE-GTN350, (ⅱ) TE-GTX400/TE-GTN350 and (ⅲ) TE-GTX400/TE-GTX400. Apart from geotextile filters, clean sediments were incorporated onto the filters, and these sediments may act as adsorbent materials for nutrients and enhance the treatment efficiency. Due to filtration, the total P (TP) content was reduced from 40 μg L~(-1) to 10 μg L~(-1), which is the safest level of P for the protection of aquatic life in Quebec surface waters. Overall TP removal efficiency by filters was between 62.5 and 75% and a slightly higher efficiency was observed with TE-GTN350/TE-GTN350 combination. Apart from TP removal, these filters were effective in reducing the turbidity by 77-85% and total N (TN) by 37-52%. The water quality improved in terms of nutrients and turbidity removal rendering an effective treatment system with potential for on-site testing as the next step.