Hongxiang Chai

Efficiency influence of exogenous betaine on anaerobic sequencing batch biofilm reactor treating high salinity mustard tuber wastewater

When treating a composite mustard tuber wastewater with high concentrations of salt (about 20 g Cl− L−1) and organics (about 8000 mg L−1 COD) by an anaerobic sequencing batch biofilm reactor (ASBBR) in winter, both high salinity and low temperature will inhibit the activity of anaerobic microorganisms and lead to low treatment efficiency. To solve this problem, betaine was added to the influent to improve the activity of the anaerobic sludge, and an experimental study was carried to investigate the influence of betaine on treating high salinity mustard tuber wastewater by the ASBBR. The results show that, when using anaerobic acclimated sludge in the ASBBR, and controlling biofilm density at 50% and water temperature at 8–12 °C, the treatment efficiency of the reactor could be improved by adding the betaine at different concentrations. The efficiency reached the highest when the optimal dosage of betaine was 0.5 mmol L−1. The average effluent COD, after stable acclimation, was 4461 mg L−1. Relative to ASBBR without adding betaine, the activity of the sludge increased significantly. Meanwhile, the dehydrogenase activity of anaerobic microorganisms and the COD removal efficiency were increased by 18.6% and 18.1%, respectively.

Effects of volumetric load in an anaerobic sequencing batch biofilm treating industrial saline wastewater

Mustard tuber wastewater is of high salinity ([Cl−1] = 18∼23 g L−1), high organic content (chemical oxygen demand, COD = 4000 ± 100 L−1) and biodegradability (BOD5/COD ≈ 0.5). The anaerobic sequencing batch biofilm reactor (ASBBR) pre-treatment, an important step to meet national discharge standard, was applied to reduce much of the organics in mustard tuber wastewater. The experiment for the effect of the volumetric load on ASBBR treating mustard tuber wastewater was conducted at different hydraulic retention times (HRTs) and volumetric exchange ratios (λ). The ASBBR operating at 50% biomass density, 30 °C, influent COD concentration of 4000 ± 100 mg L−1 and pH value of 7.0 ± 0.2, the effluent COD concentration increased from 0.22 to 4 kgCOD m−3d−1 when the volumetric load increased from 100 to 1520 mg L−1. The effluent COD concentration differed when adopted different HRT and λ under the same volumetric load. And given certain influent levels, a higher performance of ASBBR could be achieved at a lower value of HRT and λ. The optimal operational load could be determined by limiting the COD concentration under different discharge conditions, based on the results obtained in experiments.

Assessment of low concentration wastewater treatment operations with dewatered alum sludge-based sequencing batch constructed wetland system

Competition of volatile fatty acids between anoxic denitrification and anaerobic phosphorus release is prominent. Therefore, low concentration wastewater has restricted effects on nitrogen and phosphorus removal. The purpose of this study is to treat dormitory sewage with a biochemical oxygen demand (BOD) ranging from 50 to 150 mg/L using dewatered alum sludge-based sequencing batch constructed wetland system. Vegetation in the wetland system was chosen to be Phragmites australis. Three parallel cases were carried out to assess impacts due to different hydraulic retention time (HRT) and artificial aeration. The results showed that this system is effective in removing total nitrogen (TN), ammonia nitrogen (NH3-N) and total phosphorus (TP) under different HRT. However, nitrous oxide (N2O) emission poses to be the greatest challenge in the high HRT cases. Artificial aeration could reduce N2O emission but is associated with high operational cost. Results indicate that dewatered alum sludge-based sequencing batch constructed wetland system is a promising bio-measure in the treatment of low concentration wastewater.

Influence of organic loading rate on integrated bioreactor treating hypersaline mustard wastewater

Mustard tuber wastewater is characterized by high salinity and high organic content that is potentially detrimental to the biological treatment system and affects the treatment efficiency accordingly. The experiment used the integrated bioreactor to reduce much of the organics in mustard tuber wastewater, and found the influence of organic loading rate on effluent chemical oxygen demand (COD) and phosphate (PO43−‐P). Results showed that under the condition of 10–15 °C, 6 mg/L of dissolved oxygen, the reduction value of COD removal rate in anaerobic and aerobic area was 14.5% and 31.7% when the organic loading rate increased from 2.0 to 4.0 kg COD/m3/day. Therefore, an integrated bioreactor should take 2.0 kg COD/m3/day organic loading rate in mustard wastewater treatment if the effluent is expected to meet the third level of “Integrated Wastewater Discharge Standard” (GB 8978‐1996).

Enhancement of Organic Matter Removal in an Integrated Biofilm-Membrane Bioreactor Treating High-Salinity Wastewater

High salinity can strongly inhibit microbial activity and decrease the sedimentation ability of activated sludge. The combination of biofilm and membrane bioreactor is a practical approach towards effective removal of pollutants and low fouling rate. An integrated biofilm-membrane bioreactor (BMBR) treating mustard tuber wastewater was investigated. An average COD removal efficiency of 94.81% and ammonium removal efficiency of 96.84% were achieved at an organic load of 0.5 kg COD/(m3·d). However, the reactor showed a relatively low efficiency in total nitrogen and soluble phosphorus removal due to the lack of anaerobic environment. The increase of influent organic load resulted in a performance degradation because a balance between the degradation ability and pollution has been reached. Images of scanning electron microscopy revealed that halophilic bacteria were the dominant microbe in the system that leads to a loose sludge structure and declined settling properties. It was found that membrane fouling was the consequence of the interaction of microbial activities and NaCl crystallization.