Integration of an innovative biological treatment with physical or chemical disinfection for wastewater reuse

Abstract

In the present paper, the effectiveness of a Sequencing Batch Biofilter Granular Reactor (SBBGR) and its integration with different disinfection strategies (UV irradiation, peracetic acid) for producing an effluent suitable for agricultural use was evaluated. The plant treated raw domestic sewage, and its performances were evaluated in terms of the removal efficiency of a wide group of physical, chemical and microbiological parameters. The SBBGR resulted really efficient in removing suspended solids, COD and nitrogen with an average effluent concentration of 5, 32 and 10mg/L, respectively. Lower removal efficiency was observed for phosphorus with an average concentration in the effluent of 3mg/L. Plant effluent was also characterized by an average electrical conductivity and sodium adsorption ratio of 680μS/cm and 2.9, respectively. Therefore, according to these gross parameters, the SBBGR effluent was conformed to the national standards required in Italy for agricultural reuse. Moreover, disinfection performances of the SBBGR was higher than that of conventional municipal wastewater treatment plants and met the quality criteria suggested by WHO (Escherichia coli<1000CFU/100mL) for agricultural reuse. In particular, the biological treatment by SBBGR removed 3.8±0.4logunits of Giardia lamblia, 2.8±0.8logunits of E. coli, 2.5±0.7logunits of total coliforms, 2.0±0.3logunits of Clostridium perfringens, 2.0±0.4logunits of Cryptosporidium parvum and 1.7±0.7logunits of Somatic coliphages. The investigated disinfection processes (UV and peracetic acid) resulted very effective for total coliforms, E. coli and somatic coliphages. In particular, a UV radiation and peracetic acid doses of 40mJ/cm2 and 1mg/L respectively reduced E. coli content in the effluent below the limit for agricultural reuse in Italy (10CFU/100mL). Conversely, they were both ineffective on C. perfringens spores.