Abstrakt

Even after highly efficient biological processes the effluents from wastewater treatment plants may contain significant number of fecal bacteria, from 104 to 106 CFU/100 mL. Since no standards are set on the bacteriological quality of treated wastewater in Poland the elimination of bacterial contaminants is not a priority in wastewater treatment policy. Thus microbiological hazards become particularly significant in the situation when treated wastewater is discharged into the areas used recreationally. The process which guarantees the microbiological safety of treated wastewater is disinfection. In practice, all used methods are characterized by a great number of advantages and disadvantages, associated with the specific conditions of implementation and particular waste. The aim of this study is to compare the effectiveness of the three methods (ozonation, UV radiation and ultrafiltration) in disinfection of treated wastewater from full-scale wastewater treatment plan (PE - 700 000, Qav. - 96 000 m3/d). Ozonation and UV radiation are connected with inactivation of bacteria or prevention of their reproduction, while, due to the nature of membrane system, bacteria are not inactivated but removed from the treated wastewater (with other particles). Since membrane technologies are regarded as an alternative to conventional disinfection in this study, to simplify the nomenclature, bacterial removal during ultrafiltration was also considered as disinfection. In the study the disinfection was regarded as sufficient when, according to WHO standards set on wastewater reused in irrigation of crops, sports field and public parks, number of fecal coliforms reach the level below 1000 CFU in 100 mL of disinfected wastewater.

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