In this paper, the treatment efficiency of a small-scale wastewater treatment plant (WWTP) with activated sludge was analysed in order to examine the impact of variations in the composition of incoming raw municipal wastewater. The characteristics of the wastewater were analysed with respect to COD, BOD5 and TSS values and loading during the two years, 2018 and 2019. The mixed liquid suspended solid (MLSS), sludge volume index (SVI), food to microorganism ratio (F/M), sludge age and hydraulic retention time (HRT) were used for evaluation of the performance of WWTP. Removal percentage is in the order of TSS > BOD5 > COD during 2018, while in 2019 is in the order BOD5 > TSS > COD. However, better values of removal efficiency for COD, BOD and TSS are obtained in 2019, which is connected to lower oscillation values of MLSS and SVI index. Biodegradability ratio of raw and treated wastewater, plant reliability factor (RF) and equivalent number of inhabitant (ENI) were determined. In addition, the economic cost of small-scale wastewater treatment plant (WWTP) with activated sludge was evaluated and discussed.

This paper analyses the results of microbiological analyses of bathing water at the Kravica Waterfall during 2018 and 2019 and the impact of bathers on bathing water quality. The microbiological analysis of the samples was performed by the Federal Institute of Public Health in Mostar in accordance with the regulations of Directive 2006/7 EC for management of quality of bathing water. Faecal streptococci were determined using the membrane filtration method BAS EN ISO 7899-2:2003. Escherichia coli was determined using the membrane filtration method for waters with low bacterial background flora BAS EN ISO 9308-1:2015. The quality of bathing water is assessed on the basis of parameters determined by the current Directive 2006/7/EC. The number of visitors does not have a significant impact on the quality of bathing water; the reason is that of the total number of visitors there is a small percentage of bathers. During the bathing seasons in 2018 and 2019, the bathing water at the Kravica Waterfall was of excellent quality.