Assessment of N2O emission from a photobioreactor treating ammonia-rich swine wastewater digestate

Abstract

This study investigated the interactions between naturally occurring bacteria and the microalgae Chlorella vulgaris within a lab scale photobioreactor treating ammonia-rich swine wastewater digestate effluent. Nitrification and denitrification were assessed by targeting ammonia monoxygenases (amoA), nitrate (narG), nitrite (nirS), nitric oxide (norB) and nitrous oxide (nosZ) reductases genes. Oxygen produced from microalgae photosynthesis stimulated nitrification. Under limiting carbon availability (i.e., <1.44 for mg TOC/mg NO2-N and 1.72 for mg TOC/mg NO3-N), incomplete denitrification led to accumulation of NO2 and NO3. Significant N2O emission (up to 118 μg N2O-N) was linked to NO2 metabolism in Chlorella. The addition of acetate as external carbon source recovered heterotrophic denitrification activity suppressing N2O emission. Effluent methane concentrations trapped within photobioreactor was removed concomitantly with ammonia. Overall, closed photobioreactors can be built to effectively remove nitrogen and mitigate simultaneously greenhouse gases emissions that would occur otherwise in open microalgae-based wastewater treatment systems.

Swine manure digestate treatment using electrocoagulation

“…Whereas ammonia is the form of nitrogen present in the digestate (Mezzari et al, 2013), a modification in the EC reactor configuration is required to increase the removal efficiency of TN (ammonia) by electrochemical process. Mahvi et al (2011) proposed that electrodes of Al, RuO 2 /Ti and stainless steel need to be inserted in an EC reactor, to form a configuration of electrocoagulation/electro-oxidation.…”

Microbial pathways of nitrogen removal in aerobic granular sludge treating domestic wastewater

“…Total bacteria concentration, nitrifiers and denitrifiers were estimated by real‐time quantitative PCR (qPCR) analysis with primer sets and cycling conditions described in Table . For each primer set, a standard curve was constructed by serial dilutions (10 10 to 10 3 gene copies µg −1 ) of recombinant plasmid DNA containing cloned target sequences as previously described . All reaction mixtures were prepared with final concentration of primers at 250 ηmol L −1 with the qPCR‐SYBR‐Green mix/ROX kit (Ludwig Biotec, Brazil).…”

“…However, their functional pathways in nitrogen conversions (nitrification/denitrification processes) must be elucidated using alternative techniques such as real‐time quantitative polymerase chain reaction (qPCR). This method is very suitable to assess the composition of microbial communities and their ecological roles by quantifying dominant genes from biological wastewater treatment systems . However, most qPCR studies in AGS systems are related to quantification of AOB and NOB, but limited to denitrifying processes among microorganisms .…”

Elimination of Antibiotic Multi-Resistant Salmonella Typhimurium from Swine Wastewater by Microalgae-Induced Antibacterial Mechanisms

“…Scenedesmus spp. was the dominant microalgae in the PBRs as described elsewhere [9,10]. The strain was isolated and deposited in the collection of photosynthetic microorganisms for Agroenergy Research at Embrapa (Brasília, DF, Brazil) under access number Embrapa LBA#31 (IAN193.096).…”

“…Phycoremediation has been considered as an efficient tertiary treatment method to reduce organic compounds and nutrients from wastewaters [9][10][11][12]. Some microalgae produce a wide variety of antibacterial substances that can inhibit or kill pathogens [13,14].…”