Effects of slurry reflux on the stability and microbial community structure of corn stalk anaerobic digestion system

Anaerobic digestion(AD) of corn stalks with slurry reflux and non-reflux was compared and evaluated,to clarify the effects of slurry reflux on AD. The reflux of slurry increased methane production by 45.8% and also improved the buffer capacity and adaptability to high organic load rate(OLR). The results of high-throughput sequencing showed that slurry reflux increased the richness of bacterial and archaea community, and decreased the diversity of the microbial community. Slurry reflux also reduced the tendency of the enrichment of Chloroflexi and the relative abundance of Methanothrix. The increase of OLR changed the main methanogenic pathway in the anaerobic digestion system, slurry reflux could slow down this trend.

Treatment of Iraqi Municipal Wastewater by up-flow Anaerobic Sludge Blanket Reactor UASB

In this work, the Upflow Anaerobic Sludge Blanket “UASB” reactor treated effluent wastewater to investigate the process performance on a pilot plant scale. Municipal wastewater at high and medium strength with different organic load rate OLR (0.6-9) kg COD m-3day-1 with the flow of 20 l/h, up-flow velocity 0.4 m/h, hydraulic retention time HRT 9 h at a temperature of (20-30 ºC) was evaluated. The wastewater concentration, including TSS, COD was measured, and the removal efficiencies of chemical oxygen demand (COD) and total suspended solid TSS were calculated and summarized as 45-85% and 70-75%, respectively, depending on organic load rate OLR. Effluent volatile fatty acids VFA was measured, and the results were in the range between 12-90 mg/L depending on OLR with a slight change in pH (8.3-8.4), which means the conversion of COD to methane and increase ammonia concentration.

Removal of nutrients and organic pollutants from domestic wastewater treatment by sponge-based moving bed biofilm reactor

This study evaluates the efficiency of domestic wastewater treatment via Sponge-Based Moving Bed Biofilm Reactor (S-MBBR). The laboratory-based treatment plan uses polyurethane sponge with a specific surface area was 260 m²/m³ as a carrier. The treatment plan operated under four different organic load rate: OLR1 = 0.4 kg BOD/m³.day; OLR2 = 0.6 kg BOD/m³.day; OLR3 = 0.8 kg BOD/m³.day; and OLR4 = 1.0 kg BOD/m³.day. During 80 d of the experiment, the highest treatment efficiency was at the organic load rate of 0.4 kg BOD/m³.day, with COD, SS, TN and TP were found to be 85.0 ± 12.9%, 85.7 ± 5.3%, 68.9 ± 1.7%, and 40.3 ± 0.2%, respectively. In which, the influent SS concentration were from 117.3 to 126.0 mg/L, the effluent concentration were in ranged 18.0 to 34.22 mg/L, respectively. The values of influent and effluent COD were 298.8 ± 12.88 and 44.8 ± 3.78 mg/L in turn. The OLR1 influent TN, TP concentrations were respectively 47.9 ± 2.11 and 3.6 ± 0.15 mg/L; the effluent TN, TP concentration were 14.9 ± 0.18 and 2.2 ± 0.06 mg/L, respectively. The study suggests that the effluent is within the allowable limits of National technical regulation on domestic wastewater (Column B1), indicating the applicability of S-MBBR for the domestic wastewater treatment plant.

Evaluation of aerated lagoon modified with spongy support medium treating Kraft pulp mill effluent

The pulp industry generates high effluent flows, which contain high chemical oxygen demand (COD), biochemical oxygen demand (BOD5), colour and ecotoxicity. This study aimed to evaluate the treatment of Kraft pulp effluent by aerated lagoon modified with sponge support media (APG). It was assessed the arrangement of the support media in the aerated lagoons in the organic load rate (OLR) of 0.2 kgCOD m-3 d-1, and after that, with OLR variation from 0.2 to 1.2 kgCOD m-3 d-1. The parameters evaluated were BOD5, COD, colour, lignin derivatives, total phenolic compounds and acute ecotoxicity in D. magna. COD and BOD5 removals were 32% and 88%, respectively, for free and confined support media in 0.2 kgCOD m-3 d-1. There was no colour or total phenolic compounds removal under these conditions. Considering the treatment in which there was a variation of the organic load rate, 1.2 kgCOD m-3 d-1 had the best performance. In this case, 50% and 75% of COD and BOD5 were removed, respectively. Removal of colour, total phenolic compounds and lignin derivatives were around 20%, 18% and 10%, respectively. The acute ecotoxicity was reduced to toxicity factor equal to 1 in all treatments. Comparing the aerated lagoon modified systems with those without the APG, it was suggested to apply spongy support in higher organic load rate than these typically used in aerated lagoons.

Experimental Studies on Anaerobic Digestion of Straw Stalk Mixed with Pig Dung

A series of anaerobic digestion experiments on straw stalk mixed with pig dung was carried out at mid-temperature (35°C) by using the self-designed continuous stirring tank reactor (CSTR) in different organic load rates (OLR). Anaerobic digestion indexes, such as pH, ammonia-nitrogen, volatile fatty acid (VFA), total alkalinity, quantity of gas production and production rate of methane under the different organic load were studied and the aerogenic capability of the system and its stability were analyzed, so as to find the optimal organic load rate for anaerobic digestion reaction. The results show that: (1) With the OLR increases from 0.5-2.0g VS/(L·d) step by step, the pH value is always maintained 6.7-7.2; the average daily gas-production quantity is 869-3232 mL; the average ammonia-nitrogen concentration in the anaerobic digestion process has kept 522-850mg/L; the VFA concentration has remained between 1520-3420mg/L; the average total alkalinity is among 2152-2441mg/L . (2) The anaerobic digestion system is stable when the OLR increases from 0.5-2.0g VS/(L·d), and the optimal organic load rate is 1.5g VS/(L·d) for volume fraction of methane.