Effect of psychrophilic temperature shocks on a gas-lift anaerobic membrane bioreactor (Gl-AnMBR) treating synthetic domestic wastewater

Abstract

24Municipal wastewater is a renewable resource containing energy, nutrients and water. These 25 valuable constituents can be recovered via new, innovative technologies, such as the gas-lift 26 anaerobic membrane bioreactor (Gl-AnMBR), which is especially suitable for decentralized 27 wastewater treatment. To better understand the effects of fluctuating environmental conditions 28 on the treatment performance, the impact of short-term temperature shocks was studied. We 29 present a laboratory study of a 10 L Gl-AnMBR equipped with an external tubular ultrafiltration 30 membrane treating synthetic domestic wastewater at mesophilic (35 °C) conditions with a series 31 of short-term (12-48 h) cold (15 °C) shocks applied prior to switching to psychrophilic (15 °C) 32conditions. The average COD removal under mesophilic conditions was as high as 94 ± 2%, 33 even during the temperature shocks. Under the mesophilic condition, dissolved methane in the 34 effluent never exceeded 3% of the overall methane generated in the AnMBR, which is 35 considerably lower than observed during the shocks (almost 50%). Under psychrophilic 36 conditions, more than 80% of the influent COD accumulated (compared to 39% under the 37 mesophilic). Overall, results suggest that an abrupt and short-term temperature decrease from 35 38 to 15 °C can largely be absorbed by our system with no negative effect on effluent quality. 39However, gas production did not recover (after 21 d) when psychrophilic condition was 40 maintained continuously. 41 42 Keywords 43Gas-lift anaerobic membrane bioreactor; mesophilic; psychrophilic; temperature shocks; 44 dissolved methane 45 3

Anaerobic membrane bioreactor for biogas production from concentrated sewage produced during sewer mining

“…Despite the increase on VFAs in the effluent and the decrease on COD removal efficiencies, the reactor maintained its anaerobic activity and the production of biogas. This result contrasts with the study Dolejs et al (2017) in which a decrease of temperature from 34 to 15°C in an AnMBR treating synthetic municipal wastewater led to a complete inhibition of the biological processes after two weeks of operation at this temperature, confirmed by the absence of both biogas production and VFA accumulation.…”

Wastewater Treatment and Biogas Recovery Using Anaerobic Membrane Bioreactors (AnMBRs): Strategies and Achievements

“…Thus, this signifies a reduction in suspended biomass activity. Dolejs et al [53] conducted a research on the effect of psychrophilic temperature shocks on a gas-lift anaerobic membrane bioreactor (Gl-AnMBR) used for treating synthetic domestic wastewater. The stability of the system was measured by transiting between mesophilic and psychrophilic stages having several psychrophilic shocks (12-48 h).…”

Anaerobic Membrane Bioreactors for Municipal Wastewater Treatment: A Literature Review

“…Temperature fluctuations have an important effect on anaerobic degradation. Mesophilic bacteria are resistant to fluctuations of ±3 • C, but thermophiles are more sensitive and require longer adaptation to new conditions [22].…”

“…Other types include bioreactors, such as the gas-lift AnMBR, sponge AnMBR and sponge-granular AnMBR, as well as the AnMBR bioreactors used in research without their type being mentioned in the published articles. Dolejs et al investigated the effect of temperature shocks on the gas-lift AnMBR and reported that the gas-lift AnMBR was particularly suited to decentralized wastewater treatment [22]. The system efficiently operated (COD removal >80%) even after short-term decreases to 15 • C.…”

“…This could be explained by the increase of solubility of methane in water at lower temperatures. Thus, more methane escapes the reactor with the effluent decreasing the proportion of methane in biogas [3,21,22,50,125]. In AnMBR, the removal of soluble COD is mainly due to the microorganisms, and biofilm can produce additional methane.…”