| Abstract [eng] |
Water usage in cooling systems as well as in household appliance use and cleaning is a main cause for food industry sewage [1]. Wastewater collected after wheat starch production is filled with various organic substances. Some of them are really hard to decompose such as carbs, proteins and fats. These type of sewage especially has high consistency of nitrogen and phosphorus, so this type of wastewater is perfect for biological wastewater treatment, which is really economic and environmental friendly. Biological wastewater treatment is based on ability of microorganisms to decompose organic substances and make them non-organic [2]. This master thesis analyze wastewater of one of the biggest wheat starch recycle companies in Lithuania. Company produces range of starch, syrup and farm feed. Thesis analyses syrup, MVR, T8 and general sewage of companies production. Within 2 months 16 quality parameters of wastewater was analyzed. Nine of them examined in Kaunas university of Technology laboratory, five in laboratory of company itself, one in laboratory of Agrochemical Research Center and one in LLC “Kauno Vandenys” laboratory. Analytical methods were set for analyses of wastewater composition. The goal of master thesis is to analyze companies of grain recycle sewage and come up with solution for improvements. After laboratory tests it occurred that in different ways emitted sewage composition is different in every flow. Although in all taken samples were found organic substances which could possibly be processed biologically. All of this is proved by chemical oxygen and biochemical oxygen consumption ratio which in all different samples is lower than 3. Sewage has enough of nutritional materials therefore it does not need extra nutritional salts. All taken samples has a quite different pH level too. Highest level of pH was found in MVR samples (13). Lowest in samples of syrup wastewater (4,7). These sources of wastewater are not suitable for biological treatment. Yet pH of general sewage was right for treatment (6,5). After comparing the obtained parameter values to the norm found in sewage regulations standards it becomes clear that general sewage has to be treated before releasing it into the natural environment or waste collection systems. If treating waste biologically, a mix of aerobic and anaerobic methods would show the greatest performance. One of the best methods to treat wheat starch production waste is to use upflow anaerobic sludge bed reactor (UASB) or extpanded granule sludge blanket (EGSB) For aerobic method of treating waste granular activated sludge in sequential batch reactor can be adapted. In order to achieve even greater results in waste treatment extra carrier material can be used, so higher biomass concentration can be retained inside of the reactors [3,4]. Huge fluctuation or sudden alteration of flow is unfavorable for biological waste treatment. Fluctuations of pollution concentration parameters are not suitable. Therefore T8 sewage can not be treated biologically. Another unfavorable factor is high density of nitrate in both general and syrup waste. In general sewage there is high level of total suspended solids. If level of sulfate is too high it can negatively affect development of biogas. Present to anaerobic conditions occurred hydrogen sulfide can be toxic to biomass within biological wastewater treatment. It is possible to combine T8 and syrup sewage in order to optimize pH (pH of syrup is acidic, T8 pH is alkaline) and other parameters concentration. Useful compounds such as proteins or biogas can be recovered by biologically treating sewage. When applying activated sludge method during the aerobic step, large amounts of sludge are forming which have to be treated. However, the treatment can be directed to obtain phosphorus, nitrogen and protein. Biogas emissions during sludge decomposition as well as aerobic waste treatment can be used as a source of heat and electricity. Whereas research object sewage has a lot of easily biologically treatable organic materials there is usable high output of methane [5]. |
