Abstract
Abstract
Implementation of water demand reduction strategies may impact downstream water quality. These practices and impacts are particularly important for arid west regions with frequent water supply shortages. Downstream water quality impacts on indoor conservation, source separation, and graywater and effluent reuse were quantified for an arid water system where receiving water stream is predominantly fed by snowmelt and experiences large fluctuations in flow. Estimates of indoor conservation indicate that, without wastewater treatment facility (WWTF) process modifications, conservation practices implemented during drought conditions to stretch a water supply will result in an increase in receiving water body nutrient concentrations (>25% increase in total nitrogen [TN] and total phosphorous [TP]). Graywater reuse practices for toilet flushing or irrigation have negligible impacts on WWTF performance and downstream water quality even with wide adoption of the practice (100% population adoption). Conversely, adoption of source separation is estimated to notably improve influent nutrient loading, which corresponded to an improvement in WWTF effluent loading. To meet potential stream standards, city-wide adoption of source separation would be necessary and there are likely more cost-effective and feasible opportunities for improvements at the WWTF. The downstream impact of WWTF effluent reuse is largely dependent on the receiving water body and seasonality of flows, but the practice is beneficial during mid-range flow and dry conditions when effluent reuse is most valuable as an additional supply (>25% decrease in TN and TP). However, water reuse does not provide a benefit to the WWTF under concentration-based permits.
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