Reject Water: Treating of Process Water in Large Wastewater Treatment Plants in Germany—A Case Study

Abstract

The increase of the hydraulic loading of a municipal wastewater treatment plant caused by the sludge dewatering process is of minor importance. However, the rejected nitrogen load accounts for up to 25% of the nitrogen load in the raw sewage. As a result, the process water significantly influences the stage volume of the biological treatment steps. Rejection management can prevent critical nitrogen concentrations in the effluent of the plant. In some cases, the treating capacity must be increased. Separate treatment of the process water can be an alternative to the enlargement of the main wastewater treatment stages. This article describes the compositions of the process waters from different sludge treatment steps, the influence on the main wastewater treatment steps, possible strategies to handle the rejection problem, and processes for separate treatment of the sludge liquor. Some results of a German case study on large wastewater treatment plants illustrate the situation concerning separate process water treatment in Germany. These results suggest that side stream treatment can be a practical alternative to a classic increase in the length of the main stream stages. Moreover, they prove that many different processes are useful for the separate treatment of sludge liquor.

Comparative evaluation of the biochemical methane potential of waste activated sludge acetic acid and cellulose substrates under mesophilic and thermophilic anaerobic digestion

“…The Nammon is lower by comparison to a case study in Germany, which is 650 mg/l for an activated sludge that was actually from a waste stream high in nitrogen content. Conversely, the CODt of the sludge sample in our case falls between the CODt of raw sewage sludge and WAS as reported by Zanetti et al and Meyer and Wilderer [21,22].…”

Enriched Microbial Communities for Ammonium and Nitrite Removal from Recirculating Aquaculture Systems

“…1a). When anaerobically treated sewage sludge is dewatered, reject water is generated that contains high concentrations of ammonium [32]. The concentration of ammonium and nitrate was highest in raw reject water sample which we refer to as WW1.…”

Application of SS-VF Bed for the Treatment of High Concentrated Reject Water from Autothermal Termophilic Aerobic Sewage Sludge Digestion

“…However, the ammonia nitrogen load in this reject water exceeds its load in the municipal sewage. In the municipal WWTPs applying the typical stabilization processes, the load of total nitrogen in the reject water does not exceed 25% of its load in raw sewage [Janus & van der Roest 1997, Meyer & Wilderer 2004, Fux et al 2006. According to Ryzińska [2006] and Rosenwinkel et al[2009], the share of biogenic compounds load might consitute from 10 to 30% of load in raw sewage, whereas the share of ammonia nitrogen varied from 1 to 50%.…”