Department of Applied Ecology and Animal Hygiene, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 21 January 2018; accepted for publication 2 April 2018)
Abstract. The purpose of the present study was to make wastewater characterization by physico-chemical parameters from two wastewater treatment plants (WWTPs) – Municipal WWTP (MWWTP) and Poultry meat processing enterprise WWTP (PMPEWWTP). The investigation was carried out during 2016 and 11 wastewater parameters (ToC, pH, EC, SS, COD, BOD and total forms of N, P, K, Na and chlorides content) were controlled in 4 monitoring points (MPs) at both WWTPs: MP-1 – inlet of WWTP, MP-2 – after section of biological treatment, MP-3 – outlet of vertical precipitators and MP-4 – outlet of WWTP. Wastewater samples were collected every two months from each MP and were analyzed by validated Bulgarian State and ISO standards. The following were recorded: a) the value limit variation at the surveyed parameters and their characteristics by monitoring points in both treatment plants; b) that both TPs demonstrated high removal efficiency (81.6-98.6%) in regard to SS, COD, BOD5, Total N and Total P, and very low removal efficiency in regard to Total K (2.2-12.5%); c) that the final effluents from both TPs meet the ecological requirements for discharge in the receiving water bodies (Bedecka River and Azmaka River, respectively) for the parameters SS, COD, BOD5 and TN and deviate from them by phosphorus content that exceeds the permitted limit; d) that in MWWTP there are 25 correlations (15 positive and 10 negative) between monitored WW parameters and in PMPEWWTP – 28 correlations (19 positive and 9 negative), respectively; e) that there are different trends in the changes of the controlled physicochemical parameters by monitoring points and by months in both WWTPs determined on the basis of a regression model – a polynomial of degree II; f) that Na, Cl, COD and BOD5 WW content correlates very well with some other parameters, which allowed the development of linear regression models to determine their concentrations.