Characterisation of organic fractions of pulp and paper mill wastewater with a manometric respirometric biochemical oxygen demand method and automatic chemical oxygen demand analyses

The manometric respirometric method was applied to a characterisation of organic material in pulp and paper mill wastewater, which is usually high in organic content and inhibitory substances. Preliminary tests, including experiments with an extra microbial seed as well as dilution series, were carried out before the characterisation analyses in order to optimise the method. Three different physical-chemical methods were then used to characterise organic fractions. Influent organic fractions were specified with two methods in which the determination of the soluble biodegradable and the soluble inert fraction differed. In the third method, the influent fractions as well as the new metabolic products generated during the biodegradation process and an estimate of the mineralised part of the influent biodegradable fraction were determined without any hypothetical conversion factors. The results showed that a remarkable part of the detected oxygen demand was consumed for the biotransformation of biodegradable fractions into new inert organic products, not only for mineralisation. The amount of these new metabolic products, measured after biochemical oxygen demand analyses, was significant. It was also noticed that volatile organic compounds can have an influence on the chemical oxygen demand value of effluents.