A field study of advanced municipal wastewater treatment technology for artificial groundwater recharge

Field studies were conducted to investigate the advanced treatment of the municipal secondary effluent and a subsequent artificial groundwater recharge at Gaobeidian Wastewater Treatment Plant, Beijing. To improve the secondary effluent quality, the combined process of powdered activated carbon adsorption, flocculation and rapid sand filtration was applied, which could remove about 400 dissolved organic carbon （DOC） and 70% adsorbable organic halogens. The results of liquid size exclusion chromatography indicate that in the adsorption unit the removed organic fraction was mainly low molecular weight compounds. The fractions removed by the flocculation unit were polysaccharides and high molecular weight compounds. The retention of water in summer in the open recharge basins resulted in a growth of algae. Consequently, DOC increased in the polysaccharide and high molecular weight humic substances fraction. The majority of the DOC removal during soil passage took place in the unsaturated area. A limited reduction of DOC was observed in the aquifer zone.

Transformation of erythromycin during secondary effluent soil aquifer recharging:Removal contribution and degradation path

Erythromycin（ERY）,a widely used antibiotic,has recently been detected in municipal secondary effluents and poses serious threats to human health during wastewater reusing.In this study,the removal,fate,and degradation pathway of ERY in secondary effluent during soil aquifer treatment was evaluated via laboratory-scale SAT tests.Up to a 92.9%reduction of ERY in synthetic secondary effluent was observed in 1.0 m depth column system,which decreased to 64.7%when recharged with wastewater treatment plant secondary effluent.XRD-fractionation results demonstrated that the transphilic acid and hydrophobic acid fractions in secondary effluent compete for the adsorption sites of the packed soil and lead to a declined ERY removal.Moreover,aerobic biodegradation was the predominant role for ERY removal,contributing more than 60%reduction of ERY when recharged with synthetic secondary effluent.Destruction of 14-member macrocyclic lactone ring and breakdown of two cyclic sugars（L-cladinose and D-desosamine） were main removal pathways for ERY degradation,and produced six new intermediates.

Treatment of Organic Compounds in Reclaimed Wastewater for Groundwater Recharge

To study water quality problems associated with groundwater recharge, a tertiary treatment process, consisting of coagulation, sand filtration, and granular activated carbon (GAC) adsorption, was used in combination with a simulated soil aquifer treatment. The process significantly improved secondary effluent quality. GAC adsorption reduced organic substances expressed by UV-254, dissolved organic car-bon as well as partially adsorbable organic halogens. The results of the Ames test show that the secondary effluent contains a high concentration of mutagens. GAC filtration removed adsorbable organic bromine slightly whereas GAC adsorption removed mutagens effectively. The simulated soil aquifer treatment was able to further reduce UV-254, dissolved organic carbon, and adsorbable organic halogens through biodeg-radation. Adsorbable organic bromine levels were also reduced by the soil aquifer treatment process. The given reclamation technology used for groundwater recharge is of benefit to the removal of dissolved or-ganic carbon, UV-254, adsorbable organic halogens, and mutagenicity.

Removal of Organic Pollutants in Municipal Wastewater for Artificial Groundwater Recharge

In order to construct a demonstration artificial groundwater recharge system for wastewater reuse in China, three years of laboratory work has been conducted on advanced treatment technologies in combination with soil aquifer treatment of secondary effluent from sewage treatment plants. An effective and inexpensive process was selected, which uses DGB adsorption, PAC coagulation, sedimentation, sand filtration, ozone disinfection, and soil aquifer treatment. The effluent meets the recommended water quality criteria for groundwater recharge. Ozonation is effective for disinfection as well as for water quality improvement. Results showed that the total N in the SAT system remained constant thus the secondary effluent must have a low NH 3—N concentration for groundwater recharge.