The aim of the study was to determine the impact of selected factors on the reduction of organic pollutants, expressed in BOD5 and CODCr, 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 Qh1 = 0.073 m3·m-2·h-1 and Qh2 = 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.
Phosphorus removal and recovery from domestic wastewater is urgent nowadays. A novel process of nutrients removal coupled with phosphorus recovery from domestic sewage was proposed and optimization of induced crystallization reaction was performed in this study. The results showed that 92.3% of phosphorus recovery via induced Hydroxyapatite crystallization was achieved at the optimum process parameters: reaction time of 80 min, seed crystal loads of 60 g/L, pH of 8.5, Ca/P mole ratio of 2.0 and 4.0 L/min aeration rate when the PO43--P concentration was 10 mg/L in the influent, displaying an excellent phosphorus recovery performance. Importantly, it was found that the effect of reaction temperature on induced Hydroxyapatite crystallization was slight, thus favoring practical application of phosphorus recovery method described in this study. From these results, the proposed method of induced HAP crystallization to recover phosphorus combined with nutrients removal can be an economical and effective technology, probably favoring the water pollution control and phosphate rock recycle.