Abstract
Conventional quality parameters such as Chemical Oxygen Demand (COD) or Biochemical Oxygen Demand (BOD) give information about the quantity of organic matter present in wastewater, but do not give a clear indication of the biodegradability of the pollutants flowing in the WWTP. Detailed knowledge can be obtained by dividing the total COD into fractions. Fractionation and balancing of COD can be determined in various ways and with varying accuracy. Good wastewater characteristics are obtained on the basis of COD fractionation in accordance with ATV-A 131 guidelines, especially when the wastewater characteristics are in high compliance with the assumptions of the method. The article proposes a modification of the ATV-A131 method that increases the accuracy of determining the COD fraction. In order to reduce errors in the calculation of COD fractions, the value of fraction XS was calculated on the basis of the biochemical degradation rate determined in studies (k) for raw wastewater, whereas the SI fraction was calculated from the difference between SCOD and BODTot of filtered treated wastewater. BODTot of the treated wastewater was calculated taking into account the rate of biochemical degradation determined in the studies (k) for treated wastewater. The shares of individual COD fractions in raw wastewater calculated on the basis of the standard and modified procedure differed by approx. 10% in the case of suspension fractions. Modification of the methodology to determine the COD of the treated wastewater SS fraction significantly influenced the contents of all fractions in treated wastewater.
Highlights
The basis for the design and optimization of biological treatment processes is a properly prepared balance of pollutants in raw wastewater
The methods of determination of biodegradable fractions [1,17,18,19] described in the literature require a long time to obtain a result and additional analytical procedures deviating from standard determinations carried out in raw wastewater
Initial estimation of wastewater biodegradability based on the value of the Chemical Oxygen Demand (COD)/BOD5 ratio in raw and treated wastewater, combined with a COD removal, allows to control the correctness of the biochemical process of oxidation of organic pollutants contained in wastewater
Summary
The basis for the design and optimization of biological treatment processes is a properly prepared balance of pollutants in raw wastewater The effectiveness of these processes is determined by the content of biodegradable substances, which are a source of energy or a building material for microorganisms. The content of organic compounds in wastewater can be expressed indirectly as Total Organic Carbon (TOC) based on the amount of carbon dioxide produced during combustion [3,4]: Corg + O2 temp,catalyst → CO2 (1). Another method is determining the content of organic compounds based on total oxygen demand (TOD). Decompose organic substances non-oxidized in the COD method
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