The article discusses the impact of nutrients from sewage on the state of the sewage receiver. Bioremediation was carried out through the use of effective microorganisms. The potential recovery of valuable mineral and organic substances in the form of fertilizers was also examined. The Słoneczko Reservoir is a bathing area and serves many people in the summertime as a place of water recreation. Water quality deteriorated intensively from 2006 as a result of illegal wastewater discharge and the impact of fecal pollution from bathers. The high concentration of nutrients in the water was the cause of the eutrophication process and blooms of cyanobacteria, which pose a threat to human health in the bathing area. The bathing area was also closed many times by sanitary services as a result of exceeding the number of Escherichia coli and Enterococcus faecalis in the water. At the bottom of the reservoir, there was a layer of sediments with a thickness of 30–70 cm. Thus, the processes of anaerobic decomposition generated odor, causing nuisance in the reservoir area. Water transparency varied from 30 to 50 cm, due to the accumulation of suspensions and biomass of planktonic algae. The reservoir was subjected to microbiological bioremediation in 2017 and 2018 to polluted water treatment and to reduce the organic content of bottom sediments. Already after the first application of biopreparations putrefactive odors and the eutrophication process disappeared at the end of the 2017 summer season. Bioremediation reduced the value of E. coli and E. feacalis to the acceptable level. After the second application in 2018, the organic fraction of the bottom sediments was reduced to a very low level and the water transparency reached the bottom (maximum depth was 2.2 m) throughout the entire bathing area. The effect of the water remediation was maintained until 2019, and the surface water quality remained at a very good level. An important aspect in this case is also the exploitation of bottom sediments, because they are rich in nutrients and organic matter, and therefore it may have some potential as a fertilizer. The recovery of nutrients can be used in plant or pot production. However, they contain compounds that degrade quickly, causing unpleasant odors and threatening the environment. Thus, they should be managed and handled in an environmentally friendly and sustainable way.

Our paper analyzes nitrogen and phosphorus removal from sewage in a biofilter. The analysis was based on the multi-variant simulations of the combined system: fixed-film – activated sludge performance. An activated sludge ASIM 2d model related with the model of pollutions’ transformations in fixed film was used for the calculations. The results of exploitation analyses performed on the objective treatment plant – average daily rate of wastewater, pH, COD values, total suspended solids, total Kjeldahl nitrogen, nitrate nitrogen, total phosphorus, and alkalinity – were used as input parameters for the calculations. The results indicated that there is a possibility of including fixed-film in the activated sludge technology in order to improve nitrogen and phosphorus removal from the sewage. The nitrification process will be performed in fixed-film, whereas nitrogen and phosphorus removal from the sewage will be performed in anoxic chambers, which operate in the activated sludge technology. Denitrifying the dephosphatation process guarantees the high level of total phosphorus reduction (81%) and the 42% total nitrogen reduction, but only if the whole easily decomposable substrate will be consumed by microorganisms in the anoxic chamber and if enough nitrates will be present in the environment.

The paper analyzes the effect of precipitation water that inflowing to sanitary sewage system as accidental water on the changes in the total amount of treated sewage. The effects of accidental water supply on the total amount of sewage inflowing to treatment plant were analyzed based on mean daily amounts from the investigated periods and mean daily amounts from incidental supplies. The study was conducted in the years 2010–2015. Six characteristic research periods were identified (one per each calendar year), when the amount of sewage in the sanitary sewage system was greater than during dry weather. The analysis of changes in the amount of sewage supplied to the sewerage system in the six investigated periods revealed that the accidental water constituted from 26.8% to 48.4% of total sewage inflowing to the wastewater treatment plant (WWTP). In exceptional situations, during intense rains, the share of precipitation water in the sewerage system would increase up to 75%. Then, the rainwater inflowing the sewerage system caused hydraulic overloading of the WWTP by exceeding its maximum design supply.

COD is an arbitrary indicator of the content of organic and inorganic compounds in wastewater. The aim of this research was to determine the effect of COD of industrial wastewater on the nitrification process. This research covered wastewater from acrylonitrile and styrene–butadiene rubbers, emulsifiers, polyvinyl acetate, styrene, solvents (butyl acetate, ethyl acetate) and owipian^® (self-extinguishing polystyrene intended for expansion) production. The volume of the analyzed wastewater reflected the active sludge load in the real biological treatment system. This research was carried out by the method of short-term tests. The nitrification process was inhibited to the greatest extent by wastewater from the production of acrylonitrile (approx. 51%) and styrene–butadiene (approx. 60%) rubbers. In these wastewaters, nitrification inhibition occurred due to the high COD load and the presence of inhibitors. Four-fold dilution of the samples resulted in a two-fold reduction in the inhibition of nitrification. On the other hand, in the wastewater from the production of emulsifiers and polyvinyl acetate, a two-fold reduction in COD (to the values of 226.4 mgO₂·dm⁻³ and 329.8 mgO₂·dm⁻³, respectively) resulted in a significant decrease in nitrification inhibition. Wastewater from the production of styrene, solvents (butyl acetate, ethyl acetate) and owipian^® inhibited nitrification under the influence of strong inhibitors. Lowering the COD value of these wastewaters did not significantly reduce the inhibition of nitrification.

The article evaluates the effectiveness of the removal of organic pollutants—nitrogen and phosphorus—from household sewage in a hybrid bioreactor with a submerged fixed bed. The experiment was carried out in two exploitation variants that were both conducted in a laboratory model of the hybrid bioreactor: (I) cycles of 120 min of aeration and 60 min of no aeration with a constant sewage dosage, and (II) cycles 60 min of aeration and 60 min of no aeration, with a periodic sewage dosage in the no-aeration phase. The experiment was carried out on real sewage primarily treated in a septic tank. The amount of pollution removal was calculated and compared with the mandatory standards according to Polish law. Moreover, the susceptibility of the sewage to the biological treatment, nitrification, and denitrification activity was determined. The research shows a higher effectiveness for the 60/60 model in comparison to the 120/60 model. High operation efficiency was observed regarding the removal of organic pollution and nitrate nitrogen. The tested structure showed very low nitrification activity combined with intense denitrification. These processes were observed in the 60/60 variant. The structure was often overloaded with the nitrate nitrogen, which was considered to be the nitrification process inhibitor. It was suggested that phosphorus was also removed by the denitrifying bacteria.