Simple Rule-Based Algorithm for Optimizing Volatile Fatty Acids Production in Primary Sludge Fermentation Schemes

In this paper, a model-based algorithm for optimizing the primary sludge fermentation process design and operation is described and evaluated. This is a recently used method to obtain the volatile fatty acid (VFA), needed for the enhanced biological phosphorus removal process, directly from raw wastewater. The proposed algorithm consists of a heuristic reasoning algorithm based on the expert knowledge of the process. Only effluent VFA and the sludge blanket height have to be set as design criteria, and the optimization algorithm obtains the minimum return sludge and waste sludge flow rates which fulfill those design criteria. It has been evaluated by simulating different temperature and sludge volume index (SVI) influent conditions in order to evaluate the algorithm performance under different conditions, as well as its sensitivity with respect to temperature and SVI, which are the most important parameters in these systems. The same tendencies observed by simulation were observed afterward in pilot plant experiments