Removal of VOCs from Sudden Polluted Raw Water by Air Stripping

Volatile organic compounds （VOCs） are widely used in various industrial processes and generate water pollutions. VOCs removal from raw water is an important task for waterworks to guarantee drinking water security. The removal of VOCs such as chlorobenzene （CB） and ethylbenzene （EB） from raw water by air stripping was investigated under various conditions, inciuding the variation of temperature （5-30~C）, pH （3.5-10.5）, and air/water ratio （10-60）. The air stripping removal efficiency of VOCs decreased with VOCs concentration declining in water. And Henry＇s law constant was demonstrated as an indicator of the estimation of VOCs removal efficiency for air stripping. The effects of temperature and the ratio of air and water were found to play a great role in VOCs removal, but the effect of pH seemed to be negligible. This study demonstrates that air stripping provides a promising opportunity in removing VOCs in drinking water treatment, especially for the relatively high concentration of VOCs.

Nonfoaming Bubble Separation for Recovery of Butyl Acetate from Discharged Wastewater During Penicillin Production

Two nonfoaming bubble separation techniques, air stripping and solvent sublation, are presented and discussed in order to recover butyl acetate (BA) from discharged wastewater after solvent extraction of penicillin. Results show air stripping is not suitable for the recovery of BA from the wastewater. Axial concentration of BA had a noted maximum point along the column. In contrast, solvent sublation is very effective to recover BA from the wastewater. In solvent sublation experiments, axial concentration of BA along the column first increased and then decreased from the bottom to the top because of two primary mass transport processes. One is the transport by adsorption or attachment to ascending bubbles, and the other is by dispersion at water-solvent interface and by water film in organic solvent layer. In order to elucidate the high removal efficiency in solvent sublation, the microstructure of the wastewater was studied with optic microscope, which was showed to be an emulsion of BA in water at large concentration of BA. Solvent sublation can be successfully used in the removal of BA from its emulsion in the wastewater. The surface tension of simulated solution composed of lysozyme and BA was studied to understand mutual effect of biological materials and BA. Results show that lysozyme affects the adsorption of BA at air-water interface and they may form a complex between BA and lysozyme molecules.

Biodegradability enhancement of municipal landfill leachate

The method of enhancing the biodegradability of landfill leachate via air stripping followed by coagulation/ultrafiltration （UF） processes is introduced. In this study, the air stripping process obtained a removal efficiency of 88.6% for ammonia nitrogen （NH3-N）, at an air-to-liquid ratio （A/L） of 3 300 （pH = 11） and after 18 h of stripping. The single coagulation process increased the BOD （biological oxygen demand）/COD （chemical oxygen demand） ratio by 0.089 with a FeCl3 dosage of 570 mg/L, at pH 7.0, and the single UF process increased the BOD/COD ratio from 0.049 to 0.311. However, the combination of coagulation and UF increased the BOD/COD ratio from 0.049 to 0.423, and the final BOD, COD, NH3-N, and colour of the leachate were 1 023 mg/L, 2 845 mg/L, 145 mg/L, and 2 056, respectively, when a 3 kDa molecular weight cut-off （MWCO） membrane was used at an operating pressure of 0.7 MPa. In the ultrafiltration process, the average solution flux （Jv）, concentration multiple （Mc）, and retention rate （R） for the COD were 107.3 L/（m^2·h）, 6.3, and 84.2%, respectively.

Membrane combination technic on treatment and reuse of high ammonia and salts wastewater in rare earth manufacture process

With the rapid development of rare earth industry in China,high NH3-N and high salts wastewater generated in rare earth manufacture process had caused serious environment pollution especially for surrounding water body.Traditional treatment processes were either incapable of reducing pollutants concentration to the levels regulated by law or prohibitively expensive and difficult to operate.In this paper,a hybrid process which integrated air stripping pretreatment and low pressure reverse osmosis(LPRO) was proposed to treat this wastewater containing high ammonia and salt.Mechanism of treatment and remediation of ammonia and salt polluted water body was investigated.Influences of temperature,pH,and air stripping time on removal ratio of ammonia efficiencies were also discussed.Relationship among trans-membrane pressure drop(ΔP),additions ratio,stability of membrane and the possibility of water reuse were studied.The results showed that removal ratio of ammonia after LPRO desalination process could reach up to 98%,fluoride amounted to more than 99% and desalt efficiencies reached up to 95%,and stripped gas ammonia could be effectively recovered.Water quality had been improved significantly to meet reuse or discharge standards.

Study on the effect of landfill leachate on nutrient removal from municipal wastewater

In this study, landfill leachate with and without pre-treatment was co-treated with municipal wastewater at different mixing ratios. The leachate pre-treatment was achieved by air stripping to removal ammonia. The objective of this study was to investigate the effect of landfill leachate on nutrient removal of the wastewater treatment process. It was demonstrated that when landfill leachate was co-treated with municipal wastewater, the high ammonia concentration in the leachate did not have a negative impact on the nitrification. The system was able to adapt to the environment and was able to improve nitrification capacity. The readily biodegradable portion of chemical oxygen demand（COD）in the leachate was utilized by the system to improve phosphorus and nitrate removal.However, this portion was small and majority of the COD ended up in the effluent thereby decreased the quality of the effluent. The study showed that the 2.5% mixing ratio of leachate with wastewater improved the overall biological nutrient removal process of the system without compromising the COD removal efficiency.

Concentrations of disinfection by-products in swimming pool following modifications of the water treatment process:An exploratory study

The formation and concentration of disinfection by-products（DBPs） in pool water and the ambient air vary according to the type of water treatment process used. This exploratory study was aimed at investigating the short-term impact of modifications of the water treatment process on traditional DBP levels（e.g., trihalomethanes（THMs）, chloramines） and emerging DBPs（e.g., Halonitromethanes, Haloketones, NDMA） in swimming pool water and/or air. A sampling program was carried to understand the impact of the following changes made successively to the standard water treatment process： activation of ultraviolet（UV）photoreactor, halt of air stripping with continuation of air extraction from the buffer tank,halt of air stripping and suppression of air extraction from the buffer tank, suppression of the polyaluminium silicate sulfate（PASS） coagulant. UV caused a high increase of Halonitromethanes（8.4 fold）, Haloketones（2.1 fold）, and THMs in the water（1.7 fold） and, of THMs in the air（1.6 fold） and contributed to reducing the level of chloramines in the air（1.6fold） and NDMA in the water（2.1 fold）. The results highlight the positive impact of air stripping in reducing volatile contaminants. The PASS did not change the presence of DBPs, except for the THMs, which decrease slightly with the use of this coagulant. This study shows that modifications affecting the water treatment process can rapidly produce important and variable impacts on DBP levels in water and air and suggests that implementation of any water treatment process to reduce DBP levels should take into account the specific context of each swimming pool.