Novel design and optimisation of a nitritation/anammox set-up for ammonium removal from filtrate of digested sludge.

Although the anammox process is extensively applied for the treatment of NH4-rich wastewater, new technical solutions overcoming the operational difficulties remain an important task. An innovative design of anammox-based set-up was employed to improve sludge settling under high ammonium load. The set-up included a completely mixed bioreactor with suspended and immobilised activated sludge.

Comparison of different thickening methods for active biomass recycle for anaerobic digestion of wastewater sludge.

The effect of returning solids to the digester, after one of three thickening processes, on volatile solids reduction (VSR) and gas production was investigated. Three different thickening methods were compared: centrifugation, flotation and gravitational sedimentation. The amount and activity of retained biomass in thickened recycled sludge affected the efficiency of digestion.

Anaerobic thermophilic digestion of sewage sludge with a thickened sludge recycle.

The process of anaerobic thermophilic digestion of municipal wastewater sludge with a recycled part of thickened digested sludge, was studied in semi-continuous laboratory digesters. This modified recycling process resulted in increased solids retention time (SRT) with the same hydraulic retention time (HRT) as compared with traditional digestion without recycling. Increased SRT without increasing of HRT resulted in the enhancement of volatile substance reduction by up to 68% in the reactor with the recycling process compared with 34% in a control conventional reactor.