Biodegradation of potentially harmful compounds in wastewater treatment

Abstract

To study Potentially Harmful Compounds (PHCs) in the environment and their fate in Wastewater Treatment Plants (WWTPs) is a growing area of interest among researchers. Persistent Organic Pollutants (POPs) and Endocrine Disruptive Compounds (EDCs) are a concern together with Pharmaceuticals and Personal Care Products (PPCP). While advanced treatments are being considered, the fate of compounds in activated sludge is important to understand. Biodegradation is the only way of entirely removing PHCs in WWTPs and stopping them from ending up in the environment.

In this thesis a laboratory scale Sequencing Batch Reactor (SBRs) with four parallel reactors was built and the operation optimized. Sludge from the Suomenoja WWTP was used to start the reactors and they were then fed with synthetic wastewater. The operational conditions were chosen to be typical values in Finnish WWTPs. A marker compound, ibuprofen, was chosen to be studied in the reactors. The objective was to verify laboratory procedures and obtain a primary biodegradation rate and biodegradation rate constant of the compound. Ibuprofen is a non-steroidal acidic anti-inflammatory drug that is largely used in Finland and found in environmental waters as well as in WWTPs.

The synthetic wastewater was spiked with ibuprofen on four occasions. Samples from the reactors were taken at different times during aeration to analyse the ibuprofen concentration. This way the biodegradation rate and biodegradation rate constant (k_biol) was determined for ibuprofen in the SBRs. The average biodegradation of ibuprofen in the reactors was 30-50%. A k_biol value of 1.91/gSS/d was obtained. The values obtained in the study were in good agreement with previous studies. The slightly lower value for the constant could possibly be explained by the high F/M-ratio. Further research on the biodegradation mechanisms and the effect of different treatment conditions are needed to optimize the removal of ibuprofen. Also the accuracy of the analyses needs to be improved.