Efficiently managing water circuits in sewage treatment plants

Sewage treatment plants are tasked with handling waste water safely and efficiently in challenging and changing conditions. Stricter requirements for cleaning performance, energy efficiency, and operational reliability run up against variable water quality, increasing volumes, and financial pressure in ongoing operation. At the same time, aspects such as resource recovery, heat recovery, and reliable system availability are becoming increasingly important. This creates new challenges, for example when recovering heat from waste water. The heat pumps used here contain heat exchanging units that are subjected to loads to which they are not accustomed. Solids, organic matter, fats, fibers, and biological processes all influence the flow rate, heat transfer, and plant stability. Deposits, contaminants, and fouling increase the maintenance workload and can significantly impair the efficiency of individual process steps. Reliably protecting water-carrying systems from micro- and macrofouling is crucial wherever heat exchangers, heat pump systems, or other sensitive plant technology are used. Things become even more complicated when exhaust air from sewage sludge drying in belt dryers contains ammonium. It is reacted with sulfuric acid in stripping columns, which produces ammonium sulfate in liquid form (ASS). Recent technological innovations have made it possible to concentrate this ammonium sulfate solution and to crystallize it into a usable fertilizer – a shining example of how to successfully close cycles and save resources. The specific requirements of the respective process and supply stages highlight which applications are particularly relevant in sewage treatment plants.