Across the industrial world, water use has been on the decline for decades. While the US remains a country with high per capita water use, it has been and continues to decline; and importantly has significant potential for further reduction. This reduction is driven by a combination of more efficient fixtures and appliances, and increased awareness. Decrease in water usage can also be accelerated regionally by severe drought conditions as recently seen in Texas and California. While the reduced consumption has obvious water conservation benefits in general, there are also direct and indirect impacts on both the water supply as well as wastewater conveyance and treatment infrastructure. More concentrated wastewater influents also means higher concentrations of compliance relevant problem parameters such as total and refractory nitrogen, soluble nonreactive phosphorus, total dissolved solids (TDS), and any number of emerging contaminants. Numeric effluent requirements are more difficult to meet as influent concentrations increase. Parameters such as TDS, already relevant in wastewater treatment, are bound to become problematic for direct and indirect waste reuse. Even when permits are based on total loads, higher influent TKN concentration for instance may trigger the need for additional treatment stages to meet total nitrogen limits. The impact of water conservation can be amplified by infiltration and inflow (I&I) control measures. While it may seem counter intuitive, I&I reduction can have the negative side effect of exacerbating the issue by further reducing the flow in the collection system. Locally, droughts can accelerate flow reduction through sinking ground water levels (less I&I) as well as mandatory or voluntary water use reduction. Effluent compliance aside, this can impact utilities financially through an unrecoverable loss of revenue in a flow based rate structure. The subject of water conservation verses water and wastewater infrastructure is one that the industry as a whole including utilities, engineers, and regulators have to tackle. On the nutrient removal side, especially removal to very low levels, the implications range from facility upgrades to effluent requirements that exceed current limits of technology due to higher concentration of refractory nitrogen and phosphorus.
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