COD FRACTIONS IN THE PROCESS OF MECHANICAL-BIOLOGICAL TREATMENT SEWAGE

The aim of the research was to determine the COD fraction thereof in sewage and their changes in the effluent after further treatment processes. The study was conducted in a sewage treatment plant in Bialystok (RLM> 1). In sewage the highest concentrations occurred in the suspension of the organic fractions slowly biodegradable XS (303.7 mg O2/l) and dissolved organic compounds readily biodegradable SS (263 mg O2/l). The lower amounts were irreducible fractions dissolved in sewage and suspended SI (56 mg O2/l) and XI (101.2 mg O2/l). Almost 80% of the total COD fractions were biodegradable (SS + XS). In the treated wastewater soluble fraction SI-biodegradable (56 mg O2/l) occurred in the highest concentration. The flow of wastewater by components of sewage treatment plant resulted the complete removal of biologically degradable fraction of dissolved SS. More than 94.5% of the total COD in waste water purified fractions were biologically decomposable (SI + XI). Moreover, based on the analysis of studies the following soil removal was found: BOD5 – 99.4%, COD – 92.9%, total nitrogen – 93.4%, total phosphorus – 92%. After waste water treatment, ammonia nitrogen was completely removed while the nitrate concentration increased to 4.6 mg N/dm3.