Denitrification coupled with methane oxidation in a membrane bioreactor after methanogenic pre‐treatment of wastewater

Abstract

BACKGROUND The presence of dissolved methane is an important environmental problem related to greenhouse gas emissions from wastewater treated in methanogenic bioreactors. Methane has a global warming potential of 28. For low‐strength wastewaters, such as sewage, dissolved methane could account for up to 50% of the total methane produced. Dissolved methane is easily desorbed from effluents when released into the environment or post‐treated in aerobic bioreactors. The use of dissolved methane as a carbon source for biological denitrification has been proposed as an alternative for reducing both greenhouse gas emissions and nitrogen concentrations in treated wastewater. RESULTS The effluent of a methanogenic reactor operating at ambient temperature was post‐treated in a two‐compartment biological membrane bioreactor (MBR). The first compartment consisted of an anoxic denitrification reactor in which dissolved methane was oxidized. The second compartment was an aerobic membrane filtration reactor. Up to 60% nitrogen removal and 95% methane consumption were observed. Batch experiments indicated the presence of microorganisms that were capable of denitrification using dissolved methane. CONCLUSIONS Denitrification using dissolved methane as a carbon source was feasible in an anoxic–aerobic MBR system. Denitrification resulted from a mixture of aerobic and anaerobic methane oxidizing bacteria, anammox and heterotrophic bacteria activity. © 2016 Society of Chemical Industry

An innovative wastewater treatment technology based on UASB and IFAS for cost-efficient macro and micropollutant removal

“…Series II using a column of Porapack Q 80/100 (SUPELCO). Dissolved methane concentration was measured following the method described by Sánchez et al (2016).…”

“…Most of the COD (74%) was methanized under anaerobic conditions, reducing energy consumption by saving aeration and producing biogas. A fraction of the produced methane remained dissolved in the effluent of the UASB, due to methane solubility at low temperatures [22,28]. Presence of dissolved methane is still a concern because it increases GHG emissions.…”

“…Part of the methane remains dissolved in the liquid phase (up to 25-50%) especially at temperatures below 20ºC [21]. On one hand, although aerobic treatment is the common post-treatment alternative, part of the dissolved methane is released into the atmosphere by stripping, increasing greenhouse gas (GHG) emissions of wastewater treatment [22]. On the other hand, the use of conventional nitrificationdenitrification is often limited by the low remaining organic matter after anaerobic treatment, which limits the denitrification efficiency.…”

Exploring versatile applications of nitrite/nitrate-dependent anaerobic methane oxidation through modelling and experimental investigations

“…In this manner, there was always extra methane dissipated in the effluent and off-gas, not only increasing the carbon footprint, but also proposing a safety concern for the public. So far, very few studies attempted to use dissolved methane for nitrogen removal (Alvarino et al, 2019;Silva-Teira et al, 2017;Sánchez et al, 2016). For example, Silva-Teira et al (2017) set up an upflow anaerobic sludge blanket (UASB), a pre-anoxic reactor and an aerobic reactor in sequence.…”

“…Not only can the nitrogen and dissolved methane be removed simultaneously, less external carbon addition and less greenhouse gas emission are also expected. In previous studies (Alvarino et al, 2019;Silva-Teira et al, 2017;Sánchez et al, 2016), a methane removal efficiency around 80% was achieved by using a preanoxic membrane bioreactor (MBR), whilst very less nitrogen was removed at the same time (30-60%).…”