Control methods for wastewater pH

The bachelor thesis initially deals with the process of wastewater treatment with a focus on measurement, pH control and related issues. The pH value is an important parameter in wastewater treatment, which influences physical, chemical and biological processes as well as digestate treatment processes. This paper focuses on the process of thickening of digestate from a biogas plant by evaporation, which is normally associated with the leakage of volatile ammonia into the distillate. In order to eliminate this phenomenon, four methods of pH reduction were compared, which leads to the conversion of nitrogen from the volatile undesirable form 3 to the desirable form + 4 or 3 , which does not evaporate into the distillate during the evaporation process but remains in the concentrate, thus yielding a high quality fertilizer. Of the 4 methods discussed, the nitrification method appears to be the best in terms of the quality of the fertilizer output, but its disadvantage is the long retention time. From the point of view of flue gas utilization, lowering the pH by bubbling 2 and acidification with acid is a suitable method. For cases where speed and low acquisition costs are important, pH reduction with acid is preferable, unless high operating costs are a problem. In order to assess the correct method of pH reduction for a particular biogas plant, a techno-economic evaluation and consideration of other operational constraints is required and will be the subject of future work