Pilot-scale demonstration of dissolved organic nitrogen removal from an advanced water reclamation facility using enhanced coagulation

Tayebeh Goli; Yasha Jathan; Yu Yang; Krishna R Pagilla; Eric A Marchand

doi:10.1016/j.scitotenv.2023.162864

Pilot-scale demonstration of dissolved organic nitrogen removal from an advanced water reclamation facility using enhanced coagulation

Sci Total Environ. 2023 Jun 15:877:162864. doi: 10.1016/j.scitotenv.2023.162864. Epub 2023 Mar 15.

Authors

Tayebeh Goli¹, Yasha Jathan¹, Yu Yang¹, Krishna R Pagilla¹, Eric A Marchand²

Affiliations

¹ Department of Civil and Environmental Engineering, University of Nevada, Reno, Reno, NV 89557, USA.
² Department of Civil and Environmental Engineering, University of Nevada, Reno, Reno, NV 89557, USA. Electronic address: marchand@unr.edu.

PMID: 36931510
DOI: 10.1016/j.scitotenv.2023.162864

Abstract

Most wastewater treatment facilities that satisfy stricter discharge restrictions for nutrients, remove dissolved inorganic nitrogen (DIN) species efficiently, leaving dissolved organic nitrogen (DON) to be present at a higher proportion (up to 85 %) of total nitrogen (TN) in the effluent. Discharged DON promotes algae growth in receiving water bodies and is a growing concern in effluent potable reuse applications considering its potential to form hazardous nitrogenous disinfection byproducts (N-DBPs). Enhanced coagulation is an established process in the advanced water treatment train for most potable reuse applications. However, so far, no information has been collected at the pilot scale to address DON removal efficiency and process implications by enhanced coagulation under real conditions. This study performed a comprehensive evaluation of DON removal from the effluent of the Truckee Meadows Water Reclamation Facility (TMWRF) by enhanced coagulation over the course of 11 months at the pilot scale. Three different coagulants (aluminum sulfate (alum), poly‑aluminum chloride (PACl), ferric chloride (FC)) and a cationic polymer coagulant aid (Clarifloc) were used. Optimum doses for each coagulant and polymer and ideal pH were determined by jar tests and applied at the pilot. Alum (24 mg/L) resulted in highly variable DON removal (6 % - 40 %, 21 % on average), which was enhanced by the addition of polymer, leading to 32 % DON removal on average. PACl (40 mg/L) and FC (100 mg/L) resulted in more consistent DON removal (on average 45 % and 57 %, respectively); however, polymer addition exerted minimal enhancement for these coagulants. Overall, enhanced coagulation effectively reduced DON in the tertiary effluent at the pilot scale. The treatment showed auxiliary benefits, including dissolved organic carbon (DOC) and orthophosphate removal.

Keywords: Alum; Cationic polymer; Dissolved organic nitrogen; Enhanced coagulation; Ferric chloride; Poly-aluminum chloride.