The aim of this study was to determine the impact of the temperature of wastewater in a biological reactor with activated sludge and the BOD₅/N-NH₄ ratio in the influent to the treatment plant on nitrification efficiency and the concentration of ammonium nitrogen in treated wastewater. Tests were carried out in a household wastewater treatment plant which collects and treats sewage from a school building and a teacher’s house. During the 3-year study, large fluctuations in the sewage temperature in bioreactor were noted which was closely related to the ambient temperature. There were also large fluctuations in the concentration of organic matter and the concentration of ammonium nitrogen in inflowing sewage. The influence of wastewater temperature in the bioreactor and the BOD₅/N-NH₄ ratio on the concentration of ammonium nitrogen in treated wastewater was determined using Pearson’s linear correlation. A statistical analysis showed that a 1°C decrease in the temperature of wastewater in the bioreactor increased the concentration of ammonium nitrogen in treated wastewater by 2.64 mgN-NH₄·L^-1. Moreover, it was found that nitrification depended on the ratio of BOD₅ to the concentration of ammonium nitrogen in wastewater flowing into the bioreactor. An increase in the BOD₅/N-NH₄ ratio by 1 value led to a 5.41 mgN-NH₄·L^-1 decrease in the concentration of ammonium nitrogen.

The aim of the study was to determine the impact of selected factors on the reduction of organic pollutants, expressed in BOD₅ and COD_Cr, in wastewater treated in a laboratory scale model of moving bed biofilm reactor (MBBR). The factors included in the experiment: the degree of filling the fluidized bed with biomass carriers, hydraulic load, and aeration intensity. The tested model of the bioreactor consisted of five independent chambers with diameter D = 0.14 m and height H = 2.0 m, which were filled with biomass carriers at 0%, 20%, 40%, 60%, 70% of their active volume. During the test period, hydraulic loads at the level of Q_h1 = 0.073 m³·m^-2·h^-1 and Q_h2 = 0.036 m³·m^-2·h^-1 were applied, which ensured one-day and two-day sewage retention, respectively.The said reactors were subjected to constant aeration at P₁ = 3.0 dm³·min^-1 and P₂ = 5.0 dm³·min^-1. The highest efficiency of the reduction of the analysed indicators was demonstrated by reactors filled with carriers in the degree of 40–60%. Based on the statistical analyses (the analyses of the ANOVA variations and the Kruskal-Wallis test) carried out, it was found that the studied factors significantly modified the mutual interaction in the process of reducing BOD₅ in treated wastewater of the reactors tested. The significance of the impact of the discussed factors on the values of the studied indicators in treated wastewater depends on mutual interactions between the investigated factors.

The aim of the work was to determine the technological reliability of the selected pollution indicators removal BOD5, CODCr and total suspension from the sewage treatment plant working with the bioreactor Pomiltek Mann type. Wastewater treatment plant which is a subject of this study is located in Lesser Poland, in Siepraw commune. The analysis was per-formed using the Weibull method for basic indicators of impurities, BOD5, CODCr and total suspended solids. Physico-chemical analyses of raw and treated wastewater, were carried out in the period from 2003 to 2014 (11 years). The research period included measured values of pollutions indicators in 38 samples of raw and treated sewage. For each of pollution indicators descriptive statistic, percentage reduction (��) and treatment plant reliability factors (RF) were calculated. Aver-age reduction for BOD5 and TSS was on level equal 94%, only for COD the average reduction was lower and was on level 89%. The reliability values determined by Weibull method, were: 75% (BOD5), 90% (CODCr) and 89.5% (TSS). The relia-bility results have been lower than the presented by literature source, which means that work of wastewater treatment plant in Siepraw was not satisfied in 11 years of research.