Kamila Ostrowska, Wojciech Janczukowicz, Joanna Rodziewicz, Artur Mielcarek
Uniwersytet Warmińsko-Mazurski, Olsztyn
Nowadays, high effective carbon, nitrogen and phosphorus removal based on activated sludge is the most popular method of dairy wastewater treatment. In activated sludge systems efficient nutrient compounds removal is determined by the quantity and quality of easily available forms of organic carbon. For both biological phosphorus removal and biological nitrogen removal to occur, an easily biodegradable carbon source must be present in the treating wastewater. The organic compounds used in the processes of denitrification and enhanced biological phosphorus removal (EBPR) usually are presented in treating wastewater, what is called an internal source of carbon. However, many industrial wastewater, including dairy wastewater, very often do not have sufficient amounts of carbon, in relation to the concentration of nitrate and phosphates, to ensure efficient both denitrification and biological dephosphatation processes. When biological nitrogen and phosphorus removal is limited by the availability of easily biodegradable forms of organic carbon a supplemental carbon source must be add to the wastewater, hence so-called external source of carbon should be applied to provide energy necessary for the nutrient removing bacteria to grow and perform their work. One of the most popular sources of organic carbon is acetic acid, which is one of the best available forms of carbon by denitrifying bacteria and those accumulating polyphosphates (PAO). Apart from acetic acid and acetates use is made of a number of the volatile fatty acids (VFA), including propionic acid, butyric acid, valeric acid, and such substrates as: glucose, methanol or ethanol. Since the use of chemical compounds in the form of technical products (e.g. acetic acid, citric acid) is generally expensive, cost-saving solutions are sought. According to literature data, wastewater with high COD/(N + P) ratio after acidogenic fermentation can be used as an external source of VFA in wastewater with low concentrations of easily available organic compounds treatment. The aim of this study was to determine the influence of the filtration process on the content of organic compounds (measured as COD) in relation to the concentration of nutrients (measured as the sum of TKN and TP) in process dairy wastewater, in terms of the possibility of effective VFA production. It was observed, that filtration process ensures improvement of the COD/(N + P) ratio only in wastewater from the selected sections of dairy production. The best result, if percentage increase of the COD/(N + P) ratio is considered, was obtained for the wastewater from butter production. Densification of wastewater from butter production resulted in 95% increase of the COD/(N + P) ratio without a significant increased nutrient concentration. Filtration process provided the highest COD/(N + P) ratio (219,18 mg O2/(mg N + mg P)) and reduced both nitrogen and phosphorus concentrations in the permeate from the apparatus room. The results obtained suggest, that acidogenic fermentation of wastewater from the apparatus room and butter production with high COD/(N + P) ratio can serve as an external source of VFA in biological wastewater treatment process of wastewater with low concentrations of easily available organic compounds, which ensures effective nitrogen and phosphorus removal.
proces filtracji; ilość substancji
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