Sequential operation of a hybrid anaerobic reactor using a lignocellulosic biomass as biofilm support

Luffa cylindrica (Sponge Gourd) Fibers in Treatment of Greywater: an Aerobic Fixed-Film Reactor Approach

The need for potable water consumption in urban and suburban regions can be decreased by greywater treatment and its reuse. Utilizing natural fibers may provide sustainable solutions in addressing challenges related to water resource management. In this study, a fixed-film reactor was designed with Luffa cylindrica (an annually occurring fruit) as a bio-carrier. The lab-scale reactors were configured with and without Luffa cylindrica and were run for 90 days in fed-batch mode. Scanning electron microscopy (SEM) was performed to validate biofilm production over time. Monitoring COD, nitrogen, and total phosphate removal allowed for analysis of treatment effectiveness. Results demonstrated the treatment efficiency for the experimental reactor was 70.96%, 97.02%, 92.57%, and 81.20% for COD, nitrogen, phosphate, and anionic surfactant (AS), respectively. 16 s rRNA gene sequencing of bio-carrier and control greywater samples was carried out. Many bacteria known to break down anionic surfactants were observed, and microbial succession was witnessed in the control reactor vs. the experimental reactor samples. The three most prevalent genera in the experimental samples were Chlorobium, Chlorobaculum, and Terrimonas. However, it is crucial to underscore that additional research is essential to solidify our understanding in this domain, with this study laying the fundamental groundwork.

A comparative study for hybrid UASB reactor performance using polyethylene media and luffa sponge as biofilm support

This paper study the performance of a lab-scale hybrid up-flow anaerobic sludge blanket (UASB) reactor treating low-strength synthetic wastewater using different biofilm supporting materials. Two identical reactors are constructed and operated at constant up-flow velocity of 0.1 m/hr., inflow rate of 9.76 L/d, and hydraulic retention time (HRT) of 8.26 hours. The Start-up phase, using seed sludge for existing wastewater treatment plant, lasted until the efficiency of chemical oxygen demand (COD) removal of both reactors reached 80%. Polyethylene (PE) media are added to one of the reactors and luffa sponge is used in the second reactor. Results show increased COD removal efficiency up to about 90% at 20 °C and biogas production rates from 3.8*10^-3 till 7.5*10^-3 m³ CH₄/kg COD_r using PE media. The COD removal efficiency reaches about 95% at 20 °C using luffa sponge and biogas production rates up to 6.5*10 ^-3 m³ CH₄/kg COD_r are achieved before clogging problem is observed. Effect of HRT reduction, from 8.26 to 4.13 hours, on removing clogging is investigated. Reduction in COD removal efficiencies is observed at low ambient temperatures during seasonal variations of 15-25 °C. AFM and SEM analysis are used to examine sludge granulation and biofilm formation.

Biofilm formation as a method of improved treatment during anaerobic digestion of organic matter for biogas recovery

The efficiency of anaerobic digestion could be increased by promoting microbial retention through biofilm development. The inclusion of certain types of biofilm carriers has differentiated existing AD biofilm reactors through their respective mode of biofilm growth. Bacteria and archaea engaged in methanogenesis during anaerobic processes potentially build biofilms by adhering or attaching to biofilm carriers. Meta-analyzed results depicted varying degrees of biogas enhancement within AD biofilm reactors. Furthermore, different carrier materials highly induced the dynamicity of the dominant microbial population in each system. It is suggested that the promotion of surface contact and improvement of interspecies electron transport have greatly impacted the treatment results. Modern spectroscopy techniques have been and will continue to give essential information regarding biofilm's composition and structural organization which can be useful in elucidating the added function of this special layer of microbial cells.

Robustness of anaerobes exposed to cyanuric acid contaminated wastewater and achieving efficient removal via optimized co-digestion scheme

The impact of various industrial pollutants on anaerobes and the biodegradation potentials need much emphasis. This study aims to investigate the response of anaerobic microbial systems to cyanuric acid (CA) exposure; CA is toxic and possible carcinogen. First, the long-term exposure of mixed culture bacteria (i.e., municipal sludge) to low-strength wastewater containing 20 mg/L CA was conducted in an up-flow anaerobic staged reactor. Stable performance and sludge granulation were observed, and the microbial community structure showed the progression of genus Acinetobacter known as CA degrader. Second, batch-mode experiment was performed to examine the CA biodegradability at higher doses (up to 250 mg/L of CA) in the absence and presence of glucose as a co-substrate; response surface-based optimization was used to design this experiment and to estimate the optimum CA-glucose combination. CA removal of 77-98% was achieved when CA was co-digested with glucose (250-1,000 mg/L), after 7 days-incubation at temperature of 37 °C, compared to 34% when CA was solely digested. Further, the obtained methane yield dropped when CA exceeded over 125 mg/L, though the deterioration was mitigated by addition of higher concentration of glucose. Overall, we conclude that CA is efficiently degraded under anaerobic conditions when being co-digested with readily assimilable substrate.

Effects of short- and long-term exposures of humic acid on the Anammox activity and microbial community

Humic acid has a controversial effect on the biological treatment processes. Here, we have investigated humic acid effects on the Anammox activity by studying the nitrogen removal efficiencies in batch and continuous conditions and analyzing the microbial community using Fluorescence in situ hybridization (FISH) technique. The results showed that the Anammox activity was affected by the presence of humic acid at a concentration higher than 70 mg/L. In fact, in the presence of humic acid concentration of 200 mg/L, the Anammox activity decreased to 57% in batch and under continuous condition, the ammonium removal efficiencies of the reactor decreased from 78 to 41%. This reduction of Anammox activity after humic acid addition was highlighted by FISH analysis which revealed a considerable reduction of the abundance of Anammox bacteria and the bacteria living in symbiosis with them. Furthermore, a total inhibition of Candidatus Brocadia fulgida was observed. However, humic acid has promoted heterotrophic denitrifying bacteria which became dominant in the reactor. In fact, the evolution of the organic matter in the reactor showed that the added humic acid was used as carbon source by heterotrophic bacteria which explained the shift of metabolism to the favor of heterotrophic denitrifying bacteria. Accordingly, humic acid should be controlled in the influent to avoid Anammox activity inhibition.

Performance and design considerations for an anaerobic moving bed biofilm reactor treating brewery wastewater: Impact of surface area loading rate and temperature

Three 4 L anaerobic moving bed biofilm reactors (AMBBR) treated brewery wastewater with AC920 media providing 680 m² protected surface area per m³ of media. Different hydraulic retention times (HRT; 24, 18, 12, 10, 8 and 6 h) at 40% media fill and 35 °C, as well as different temperatures (15, 25 and 35 °C) at 50% media fill and 18 h HRT were examined. Best performance at 35 °C and 40% media fill was observed when HRT was 18 h, which corresponded with 92% removal of soluble COD (sCOD). Organic loading rates (OLR) above 24 kg-COD m^-3d^-1 decreased performance below 80% sCOD removal at 35 °C and 40% media fill. The reason was confirmed to be that surface area loading rates (SALR) above 50 g-sCOD m^-2d^-1 caused excessive biofilm thickness that filled up internal channels of the media, leading to mass transfer limitations. Temperature had a very significant impact on process performance with 50% media fill and 18 h HRT. Biomass concentrations were significantly higher at lower temperatures. At 15 °C the mass of volatile solids (VS) was more than three times higher than at 35 °C for the same OLR. Biofilms acclimated to 25 °C and 15 °C achieved removal of 80% sCOD at SALR of 10 g-sCOD m^-2d^-1 and 1.0 g-sCOD m^-2d^-1, respectively. Even though biomass concentrations were higher at lower temperature, biofilm acclimated to 25 °C and 15 °C performed significantly slower than that acclimated to 35 °C.

Factors affecting on hythane bio-generation via anaerobic digestion of mono-ethylene glycol contaminated wastewater: Inoculum-to-substrate ratio, nitrogen-to-phosphorus ratio and pH

This study aims to assess the effect of inoculum-to-substrate ratio (ISR) and nitrogen-to-phosphorus balance on hythane production from thermophilic anaerobic decomposition of mono-ethylene glycol (MEG) contaminated wastewater. ISRs ranging from 2.65 to 13.23gVSS/gCOD were employed, whereas the tested N/P ratios varied from 4.6 to 8.5. Maximum methane and hydrogen yields (MY and HY) of 151.86±10.8 and 22.27±1.1mL/gCOD_initial were achieved at ISRs of 5.29 and 3.78gVSS/gCOD, respectively. HY increased 1.45-fold by decreasing N/P from 8.5 to 4.6, while MY improved 1.6-fold by increasing N/P from 4.6 to 5.5. Methane production was strongly influenced by initial NH₄-N, compared to initial PO₄-P. Optimal HY of 47.55mL/gCOD_initial was achieved at pH 5.0 and ISR of 3.78gVSS/gCOD using thermal-treated sludge. Three-dimensional regression model was applied for the combined effect of initial MEG, NH₄-N and PO₄-P on hythane production. Potential economic benefits of hythane production from MEG contaminated wastewater were assessed.