Pathogens removal in UASB-septic tanks and Albireh oxidation ditch wastewater treatment plant

Abstract

The reuse of treated effluent represents a national interest and is considered as an important component of the overall maximization of water resources in Palestine. However, all attempts on wastewater reuse not successful due to many reasons and illegal irrigation practices with partially treated effluent in certain areas still impose serious health hazards and environmental problems. Inadequate wastewater treatment facilities and lack of data on hygienic aspects of treated wastewater hampered the successful implementation of wastewater reuse schemes at the national level. The main objective of this research was to compare pathogens removal in Upflow Anaerobic Sludge Blanket (UASB)-septic tanks and Al-Bireh wastewater treatment plant (AWWTP). The UASB-septic tanks, located at AWWTP, fed continuously with raw municipal wastewater from the aerated grit chamber of AWWTP. The two pilot scale UASB-septic tanks (R1 and R2) were operated at two different hydraulic retention times (HRT) of 2 and 4 days for R1 and R2, respectively. AWWTP, as an extended aeration system with aerobic sludge stabilization, the HRT was about one day. Both raw wastewater and treated effluent were tested for microbial pathogens including indicator bacteria, protozoa and trophozoite using microscopic and specific culture media. Data obtained from this research study on Fecal coliform, Fecal streptococcus, Salmonellae Shigilla, Balantedium coli, Ascaris lumbrecoudes, Amoeba cysts, Giardia cysts, Trichuris trichiura, pathogens in the trophozoite form as Trichomonas, Strongyloides sterorlasis, Enterobius vermicularis are presented and discussed. The removal efficacies of R1 and R2 were 15.5% and 15% for Fecal coliform and 6.9% and 11% for Fecal streptococcus, respectively. While the removal efficacy of the oxidation ditch was 38% for Fecal coliform and 16% for Fecal streptococcus. Though Salmonellae was detected in 30% of analyzed influent samples, it was not detected in any sample of the effluent of both treatment systems. Also, the treated effluent of R1, R2 and oxidation ditch was parasites (cysts or trophozoites) free. The installment of a post treatment stage (disinfecting unit) in the treatment technologies under study is recommended in order to comply with national or future regional guidelines for effluent agricultural reuse or discharge into receiving water bodies.