Wastewater Primary Treatment Using Forward Osmosis Introduces Inhibition to Achieve Stable Mainstream Partial Nitrification

Abstract

Achieving stable long-term mainstream nitrite oxidizing bacteria (NOB) suppression is the bottleneck for the novel partial nitrification (PN) process toward energy- and carbon-efficient wastewater treatment. However, long-term PN stability remains a challenge due to NOB adaptation. This study proposed and demonstrated a novel strategy for achieving NOB suppression by the primary treatment of mainstream wastewater with a forward osmosis (FO) membrane process, which facilitated two external NOB inhibition factors (salinity and free nitrous acid, FNA). To evaluate the proposed strategy, a lab-scale sequencing batch reactor was operated for 200 days. A stable PN operation was achieved with a nitrite accumulation ratio of 97.7 ± 2.8%. NOB were suppressed under the combined inhibition effect of NaCl (7.9 ± 0.2 g/L, as introduced by the FO direct filtration) and FNA (0.11 ± 0.02 mg of HNO2–N/L, formed as a result of the increased NH4 +–N concentration after the FO process). The two inhibition factors worked in synergy to achieve a more stable PN operation. The microbial analysis showed that the elevated salinity and accumulation of FNA reshaped the microbial community and selectively eliminated NOB. Finally, an economic and feasibility analysis was conducted, which suggests that the integration of an FO unit into PN/A is a feasible and economically viable wastewater treatment process.

Toward Energy Neutrality: Novel Wastewater Treatment Incorporating Acidophilic Ammonia Oxidation

“…According to the energy balance, the proposed system could achieve energy self-sufficiency with a net energy production of 329 GJ/y in a WWTP with a treatment capacity of 10,000 m 3 /days (Figure ). The achievement of net energy production was due to the significant reduction of energy consumption in aeration, which agreed with previous estimations for the mainstream PN/A process. , …”

“…The achievement of net energy production was due to the significant reduction of energy consumption in aeration, which agreed with previous estimations for the mainstream PN/A process. 60,61 This study achieved the mainstream PN/A process in a twostage configuration. First, because low pH and high FNA are inhibitory to anammox bacteria, the acidic PN and anammox were separated in two tanks to avoid the inhibition of anammox activity.…”

A 20-Year Journey of Partial Nitritation and Anammox (PN/A): from Sidestream toward Mainstream

“…NOB growth rate (μ NOB ) relates to environmental factors (e.g., temperature, pH, salinity) and substrate concentrations, including dissolved oxygen (DO) and NO 2 – , via the Monod equation: The environmental factors (e.g., temperature, pH) are usually difficult to regulate given the huge volume of mainstream wastewater. As such, μ NOB is primarily decreased by restricting the availability of oxygen and/or NO 2 – to NOB.…”

“…NOB growth rate (μ NOB ) relates to environmental factors (e.g., temperature, pH, salinity 17 ) and substrate concentrations, including dissolved oxygen (DO) and NO 2 − , via the Monod equation:…”

Desalination, Water Re-use, and Halophyte Cultivation in Salinized Regions: A Highly Productive Groundwater Treatment System

“…Forward osmosis (FO) can provide an interesting solution both to integrate halophyte cultivation and to help manage wastewater. FO can be used to recover and reuse water from an effluent stream provided a suitable draw solution is available. − Seawater has already been used as a draw solution to recover wastewater and reduce energy consumption in hybrid FO–RO seawater desalination. ,,− In comparison to seawater, however, brackish groundwater is typically too dilute for direct use as a FO draw solution. Nonetheless, brackish groundwater becomes suitably concentrated as brine after RO.…”