Abstract
Water quality in San Francisco Bay is reportedly adversely affected by nitrogen loading from the wastewater treatment plants (WWTPs) discharging around the periphery of the Bay. Here, we consider a zeolite-anammox system to remove ammonia and nitrate from secondary-treated wastewater at ambient temperatures (12–30 °C). Until now, use of anammox bacteria has been largely limited to treatment of high-ammonia content wastewater at warm temperatures (30–40 °C). Specifically, we investigate upscaling the zeolite-anammox system to nitrogen removal from relatively low-ammonia content (~35 NH3-N mg/L) effluent using gravity-fed 0.7 m wide and 0.17 m deep linear-channel reactors within pilot plants located at either the WWTP or some eight kilometers away. Following establishment, we monitored ammonia and nitrate concentrations along one reactor bi-weekly and only inflow–outflow concentrations at the other for more than a year. We found nearly complete ammonia removal within the first 22 m of reactor consistent with the theoretical 89% nitrogen removal capacity associated with the nitrogen-conversion stoichiometry of anammox bacteria. We also determined degradation parameters of a constant 1.41 mg NH3-N/L per hour in the first 15 m, or 20.7 g NH3-N/m3/day for overall reactor volume. At the higher flowrate of the second reactor, we achieved a removal rate of 42 g NH3-N/m3/day. Overall, the linear-channel reactors operated with minimal maintenance, no additional energy inputs (e.g., for aeration) and consistently achieved NH3-N discharge concentrations ~1 mg/L despite fluctuating temperatures and WWTP effluent concentrations of 20–75 mg NH3-N/L.
Highlights
Water quality studies of the San Francisco Bay (SFB) estuary [1] indicate that it is adversely affected by nitrogen and phosphorous inputs from multiple anthropogenic sources [2], the greatest being nitrogen loads from wastewater treatment plant (WWTP) discharges on the Bay periphery [3]
While converting ammonia to nitrite generally lowers pH, pH varied little and posed no practical problems because of the relatively low influent NH3 concentration (~35 mg/L) with more than adequate alkalinity to buffer the systems and because both ammonia and nitrate removal occurred within the same reactor
The gravity-flow linear-channel reactors operating at Hayward Marsh and the Martinez WWTP
Summary
Water quality studies of the San Francisco Bay (SFB) estuary [1] indicate that it is adversely affected by nitrogen and phosphorous inputs from multiple anthropogenic sources [2], the greatest being nitrogen loads from wastewater treatment plant (WWTP) discharges on the Bay periphery [3].Nitrogenous waste (primarily ammonia and/or nitrate) is of particular concern in SFB, especially in the shallower reaches subject to tidal flood–drain processes. Water quality studies of the San Francisco Bay (SFB) estuary [1] indicate that it is adversely affected by nitrogen and phosphorous inputs from multiple anthropogenic sources [2], the greatest being nitrogen loads from wastewater treatment plant (WWTP) discharges on the Bay periphery [3]. State regulatory agencies noted that nutrient concentrations in SFB exceed those in other estuarine ecosystems where degradation is apparent. This observation has raised concerns that SFB may be trending toward, or already experiencing, adverse impacts due to high nutrient loads, thereby requiring greater regulation of WWTP nitrogen loading to the Bay. We consider upscaling the zeolite-anammox treatment process [4] to the commercial scale at several WWTPs around the SFB. We examine performance of a non-aerated, gravity-flow system that builds on our earlier proof-of-concept study [4]
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