Aerobic granular sludge treating anaerobically pretreated brewery wastewater at different loading rates.

In this study, three different aerobic granular sludge (AGS) reactors fed with anaerobically pre-treated brewery wastewater were studied. The AGS reactors were operated under different conditions including organic loading rates (OLR) between 0.8 and 4.1 kg COD m-3 d-1, C:N:P ratios (100:10:1 and 100:6:1) and food to microorganism ratios (F/M) between 0.8 ± 0.6 and 1.2 ± 0.5 and 0.9 ± 0.3 kg-TCOD kg-VSS-1d-1. Stable granulation was achieved within two weeks and the size of the granules increased according to the OLR applied. The results indicated that low C:N:P and F/M ratios were favorable to achieve stable aerobic granules in the long term. The carbon removal rate was load-independent in the range examined (TCOD removal >80%), whereas TN removals were inversely proportional to the OLRs. Overall, a longer aeration reaction time with a lower OLR was beneficial to granular structure, which exhibited a compact and defined architecture. Performance results within the other conditions studied further indicated that the microbial community and its complex functionality in nutrient removal was efficient at operational parameters of OLR at 0.8 ± 0.2 kg-TCOD m-3d-1 and F/M ratio at 0.5 ± 0.2 kg-TCOD VSS-1d-1. Moreover, the protein to polysaccharide ratio increased as OLR decreased, leading to a stable granular structure.

Kinetics of aerobic granular sludge treating low-strength synthetic wastewater at high dissolved oxygen.

Three parallel reactors (i.e. R1-R3) were operated with 340 mg-COD L-1, 42 mg-TN L-1, and 7 mg-TP L-1 at 20 ± 1°C. A mature granular sludge developed in 40 d and was stable for the 120 d experimentation period at an average food to microorganism ratio of 0.25 ± 0.08 g-COD g-VSS-1 d-1. Reactor biomass had higher inorganic content (i.e. 0.78-0.80 g-VSS g-TSS-1) than effluent biomass (i.e. 0.88-0.92 g-VSS g-TSS-1). Average granule diameter was 0.7-1.0 mm. Maximum phosphorus uptake and release rates averaged 4 ± 3 and 4 ± 2 mg-P g-VSS-1 h-1, respectively. Maximum observed nitrification rates averaged 1.9 ± 0.6 mg-N g-VSS-1 h-1. Phosphorus kinetics were similar between R1-R3 (i.e. P = 0.5309-0.6870) while nitrification kinetics varied significantly (i.e. P = 0.0002) even though conditions were the same. Effluent phosphate was on average 0.2 ± 0.4 mg-P L-1 while total inorganic nitrogen removal averaged 60 ± 10% resulting in an average effluent of 17 mg-N L-1. Aerobic granular sludge was capable of reliable nutrient removal from low-strength wastewater without volatile fatty acid source and at high dissolved oxygen concentrations.

Electrocoagulation of wastewater using aluminum, iron, and magnesium electrodes.

Primary influent from a municipal wastewater treatment plant was electrochemically treated with sacrificial aluminum, iron, and magnesium electrodes. The influence of sacrificial anodes on the removal of chemical oxygen demand, total nitrogen, total phosphorus, and orthophosphate during sedimentation was investigated. Nitrification kinetics were assessed on treated supernatant and biogas production was monitored on settled solids. Changes in alkalinity, conductivity, and pH were also recorded. Aluminum and iron electrodes provided high rates of orthophosphate removal (i.e., 6.8 mg-P/mmol-e). Aluminum and iron electrodes also provided similar treatment to equivalent doses of alum and ferric salts (i.e., 38-68% chemical oxygen demand, 10-13% total nitrogen, and 67-93% total phosphorus). The estimated stochiometric ratio of aluminum and iron dosed to orthophosphate removed was approximately 1.3:1 and 4.1:1, respectively. Magnesium electrodes, on the other hand, removed orthophosphate at rates 8-9 times slower than aluminum and iron (i.e., 0.9 mg-P/mmol-e). Magnesium had to be dosed at a ratio of 13.5:1 orthophosphate for phosphorus removal. Orthophosphate removal by magnesium electrodes was most likely limited by electrolysis reactions responsible for increases in pH (i.e., 0.52 pH units/mmol-e). Magnesium electrodes removed 49% chemical oxygen demand and 21% total nitrogen at the high molar ratios required for orthophosphate removal.

Effect of extended famine conditions on aerobic granular sludge stability in the treatment of brewery wastewater.

Results obtained from three aerobic granular sludge reactors treating brewery wastewater are presented. Reactors were operated for 60d days in each of the two periods under different cycle duration: (Period I) short 6h cycle, and (Period II) long 12h cycle. Organic loading rates (OLR) varying from 0.7kgCODm-3d-1 to 4.1kgCODm-3d-1 were tested. During Period I, granules successfully developed in all reactors, however, results revealed that the feast and famine periods were not balanced and the granular structure deteriorated and became irregular. During Period II at decreased 12h cycle time, granules were observed to develop again with superior structural stability compared to the short 6h cycle time, suggesting that a longer starvation phase enhanced production of proteinaceous EPS. Overall, the extended famine conditions encouraged granule stability, likely because long starvation period favours bacteria capable of storage of energy compounds.