Tailored water treatment using enhanced primary clarification for nutrient recovery and production of water for turfgrass irrigation

Abstract

An emerging strategy for urban water infrastructure includes distributed water supply, storm water management, and wastewater treatment to manage water within a utility basin. The use of reclaimed water to offset intra-basin water demand for irrigation can be a key component of such a strategy—landscape irrigation is estimated to account for up to 70% of total potable water demand. Fertigation (i.e., irrigation with nutrient-rich water) with reclaimed water is able to offset fertilizer and potable water requirements, which provides an added benefit to end-users. However, research exploring fertigation water production in a decentralized setting is sparse. Two studies to produce high-nitrogen water using a sequencing batch reactor have been described in the literature. While nitrogen concentrations were increased, the changes in treatment resulted in a very low pH in the bioreactor (<5.0) and an increase in blower energy consumption (6.1–7.0%), or required substantial changes to the treatment operation. The research presented here demonstrates a new strategy, enhanced primary clarification coupled with a sequencing batch reactor (EPC-SBR) to produce nutrient-rich water with a balanced nitrogen–phosphorus ratio for turfgrass fertigation. The EPC-SBR system was operated for 114 days and produced water with an average inorganic nitrogen concentration of 13.9 mg N L⁻¹ and an average N : P ratio of 10.5 : 1, without substantial increase in blower energy use or extreme modifications to the SBR operations.