Characteristic of raw wastewater based on cod fractions

Przedstawiono ogólną charakterystykę frakcji ChZT w ściekach surowych oraz wyniki badań stężeń frakcji ChZT w ściekach surowych dopływających do oczyszczalni o RLM > 100 000. Wyniki badań rzeczywistych porównano z danymi przyjmowanymi w modelach biokinetycznych typu ASM. W surowych ściekach oznaczano frakcje biodegradowalne SS i XS oraz niebiodegradowalne SI i XI. Stężenia frakcji wyznaczano na podstawie wytycznych ATV-A 131. Wyznaczone w warunkach rzeczywistych stężenia oraz procentowe udziały poszczególnych frakcji ChZT w ściekach surowych różnią się od danych zamieszczonych w literaturze.According to the literature the percentage of the suspension fraction in the total COD of raw municipal wastewater is 65 ÷ 79% and dissolved 21 ÷ 35%. It is also understood that the percentage of suspended solids in municipal wastewater is about 57% of COD and colloids and dissolved substances about 43%. In the biokinetic models like ASM the percentages of individual fractions in the total COD is: in ASM1 XS = 70%, SS = 15%, XI = 10%, SI = 5%, while in ASM2: XS = 35 ÷ 75%, SS = 12 ÷ 30%, XI = 10 ÷ 15%, SI = 5 ÷ 10%. The paper presents the general characteristics of COD fractions of raw wastewater and the results of COD fractions concentrations in the raw wastewater flowing into treatment plant with population equivalent > 100 000. In the raw effluent from sewage treatment plant biodegradable fractions SS and XS and non-biodegradable fractions SI and XI were determined. Concentrations of each fractions were determined on the basis of guidelines ATV A -131. During the study in the raw wastewater organic pollutants measured as CODCr values were from 528 to 768 mgO2/dm3. The values of the total COD of raw wastewater was appointed as the sum of each fraction varied from 621.0 ± 14.1 to 747.8 ± 139.2 mgO2/dm3 depending on the season. Based on the concentration of each fraction the percentage of each fraction in the total COD were determined. The values of the percentage of each fraction in total COD were compared with data received in biokinetic models like ASM. The designated real concentration of each COD fraction in raw wastewater and the percentage of each fraction in total COD are different from the data reported in the literature. The results showed that in raw wastewater in the highest concentrations occur in succession fraction XS, then SS, XI and SI. This order is consistent with biokientic models. Significant differences between the research and models assumptions concerning the range of content of each fraction. The percentage of COD fractions in the raw wastewater from wastewater treatment plant "Łącza" were set at: XS = 49.3 ÷ 53.4% SS = 23.9 ÷ 30.4% XI = 16.4 ÷ 17.8% SI = 2.9 ÷ 4.9 %. More than 75% of the total COD in the raw wastewater were biodegradable fractions (the sum of SS and XS fractions). The XS fraction accounted between 49.3 to 53.4% of the total COD and the SS fraction from 23.9 to 30.4% of the total COD. The contents of XI fraction was at 16.4 ÷ 17.8% of the total COD. The smallest share of the total COD of raw wastewater was fraction SI. The research results showed that in the raw wastewater the percentage of XI and SS fraction is higher and a the percentage of SI and XS fractions is lower compared with the assumptions in models ASM1 and ASM2. The real concentration of each fraction and the percentage of each fraction in the total COD determined in the raw wastewater should be the basis for calibrating models used in modeling and controlling the operation of the wastewater treatment plant