We propose a new technology to advanced treat overflow wastewater from a combined sewer system using a storage tank-wastewater treatment plant (STP)-constructed wetland (CW) system. The engineering demonstration (a 7,500 m(3)storage tank and a 3,436 m(2)CW) has been built to treat the combined sewer overflows (CSOs) at the largest combined rainwater/wastewater overflow outlet in the middle reaches of the Xinbaoxiang River, which is the second largest river in the Dianchi Lake Basin. During the rainfall period, CSOs enter the storage tank. After sedimentation purification, the higher concentration CSOs at the bottom enter the STP, and the upper low-concentration CSOs enter CWs, thereby linking the multiple means of treating CSOs and minimizing the impact of CSOs on the STP. During the dry season, CWs can also assist in purification of polluted river water. The supernatant (COD <80 mg/L) and the bottom part water (COD >200 mg/L) of the storage tank were sent to CWs and STP, respectively, for treatment. The project was stably operated over 6 months. The final effluent qualities were 12, 1.79, and 0.18 mg/L for COD, TN, and TP, respectively, which achieved the surface water class V standard. Practitioner points A combined system of storage tank-wastewater treatment plant-wetland was proposed to advanced treat overflow wastewater of rainy season. The SWMM could calculate the water quality and volume of overflow under different rainfall conditions in the runoff area. The effluent of the engineering demonstration reached the standard of surface water class V.

In the present study, simultaneous nitrification and denitrification of sewage treatment plant effluent was evaluated using an up-flow fixed-bed system packed with poly (3-hydroxybutyrate-hydroxyvalerate)/polylactide (PHBV/PLA) blends used in a dual role as carbon source and biofilms carrier. 98.1 +/- 2.9% and 87.2 +/- 6.8% of influent NH4+-N and NO3–N was removed from the synthetic wastewater. TN removal efficiency was 89.3 +/- 6.3% with the average effluent TN concentration of 1.6 +/- 0.9 mg/L during the stable period indicating that simultaneous nitrification and denitrification occurred. An initial high release of DOC in the effluent eventually stabilized at average of 9.0 +/- 3.4 mg/L. Simultaneous nitrification and denitrification occurred in the first 5 cm, and denitrification only in higher column sections. The PHBV/PLA supported system is a promising technology which could be applied for post-treatment of wastewater with low C/N ratios.

To explore an effective approach of simultaneous nitrification and denitrification in wastewater with low C/N ratios, integrated packed bed bioreactors based on poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) with different dosing methods were designed. The removal efficiency of NH4+-N in bioreactor with aeration was 88.62%, and higher NO3–N removal efficiency was observed in bioreactor filled with grainy PHBV (95.21%) than bioreactor filled with strip PHBV (93.34%). Microbial study indicated that microbes harboring amoA and nirS genes preferred to attach on the surface of ceramsite, and significant differences in microbial community compositions at phylum and genus levels were observed. To summarize, it is feasible to utilize grainy PHBV for simultaneous and efficient removal of NH4+-N and NO3–N from wastewater with low C/N ratios.

In this study, three pilot-scale solid-phase denitrification (SPD) systems filled with poly-3-hydroxybutyrate-co-hyroxyvelate (PHBV), PHBV-Rice hulls (PHBV-RH) and PHBV-Sawdust (PHBV-S) were operated to treat effluent of waste water treatment pangts (WWTPs). The fast start-up and intensified nitrogen removal performance were obtained in PHBV-RH and PHBV-S systems. Besides, the optimal total nitrogen (TN) removal efficiency was obtained in PHBV-S system (91.65 +/- 4.12%) with less ammonia accumulation and dissolved organic carbon (DOC) release. The significant enrichment of amx 16S rRNA and nirS genes in PHBV-RH and PHBV-S systems indicated the possible coexistence of anammox and denitrification. Miseq sequencing analysis exhibited more complex community diversity, more abundant denitrifying and fermenting bacteria in PHBV-RH and PHBV-S systems. The co-existence of denitrification and anammox might contribute to better control of nitrogen and dissolved organic carbon in PHBV-S system. The outcomes provide an economical and eco-friendly alternative to improve nitrogen removal of WWTPs effluent.