A novel method to rapidly assess the suitability of water treatment residual and crushed concrete for the mitigation of point and nonpoint source nutrient pollution

Abstract

Freshwater ecosystems worldwide are at risk of becoming degraded as a result of excessive inputs of phosphorus (P) associated with terrestrial activities. This study describes a novel methodology to rapidly assess the potential of low-cost adsorbents which might be used to combat this issue. The ability of aluminum drinking water treatment residual (Al-WTR) and crushed concrete (CC) to remove P from dairy wastewater (DW) and forestry runoff (wastewaters representative of point and nonpoint P pollution sources, respectively) was assessed. In addition to predicting the longevity of these media in large-scale filters, potential risks associated with their use were also examined. The results indicate that both CC and Al-WTR show promise for use in removing P from forestry runoff, however the raised pH of effluent from CC filters may pose an environmental concern. Al-WTR showed greater promise than CC for the treatment of DW due to its higher adsorption capacity at high concentrations. Small releases of aluminum (13.63-96.17 μg g⁻¹) and copper (5.25-31.9 μg g⁻¹) were observed from both media when treating forestry runoff, and Al-WTR also released a small amount of nickel (0.16 μg g⁻¹). Approximately 50% of total metal loss occurred during the first 25% of total filter loading, indicating that pre-washing of the media would help prevent metal release. These results indicate that field-scale tests are warranted for the treatment of both wastewaters with Al-WTR; CC is likely to be unsuitable for either forestry runoff or DW due to its effects on pH and its short lifespan.