The new form of pre-fermentation process arrangement for removing nutrients from wastewater

Summary

The concentration of readily available organic matter determines the process stability of biological phosphorus removal from wastewater. The low value of this parameter is typical for municipal wastewater in Moscow. Raw wastewater sludge pre-fermentation (acidofication) is one of the methods of increasing the readily available organic matter fraction. A new arrangement of pre-fermentation process has been implemented in the industrial-scale aeration tanks of the Moscow wastewater treatment facilities operating after the process flow scheme of the University of Cape Town (UCT). Compared to the traditional pre-fermentation process flow scheme taking place in a primary settling tank or reactor prefermenter the process is arranged in the first anaerobic zone of the aeration tank. Here, in the absence of mixed liquor mixing, a thickened layer of activated sludge is formed accompanied by pre-fermentation of organic matter sorbed onto sludge. Meanwhile the anaerobic zone carries on its main function in the treatment process related to biological phosphorus release by means of phosphate accumulating bacteria consuming volatile fatty acids. Increasing the concentration of volatile fatty acids in mixed liquor in anaerobic zone by means of pre-fermentation stabilizes phosphate removal from processed wastewater. Arranging pre-fermentation process in the first corridor of the aeration tank is more advanced and cost-effective compared to the traditional process arrangement in settlers-prefermenters owing to saving expenditures on mixing and eliminating construction or upgrade of additional tanks (prefermenters, settling tanks).

Key words

wastewater , acidification , readily available organic matter , prefermentation , raw sludge , biological dephosphatation