The Biodenipho process reduces to a minimum the content of nitrogen and phosphorus in wastewater in addition to significantly reducing organic matter (BOD), ammonia and suspended solids.

Furthermore, it eliminates odour nuisances as the sludge is stabilised in the process.

The oxidation ditch system consists of an anaerobic tank located before two interconnected biological tanks of equal volumes and a final settling tank. The biological tanks work in an alternating mode of operation and are equipped with aerators, inlet distributors and outlet chambers.

The Bio-denitro process was developed by Krüger, a subsidiary of Veolia Water Solutions & Technologies, in the 1970s as an inexpensive method of treating wastewater that consistently was able to achieve high levels of nitrogen removal. Since then the process has been developed further in order to meet new and more stringent treatment standards.

The Bio-denitro is a unique wastewater treatment process developed by Krüger. The process combines functional design with an outstanding flexibility and highly adaptable operation. As a result, the process has successfully been implemented on more than 300 installations worldwide with plant capacities up to 750,000 PE.

BIO-DENIPHO and BIO-DENITRO are biological treatment processes for removal of carbon, nitrogen and phosphorus from wastewater.

The technique used is an original application of the activated sludge principle and involves the control of a sequential treatment of pollution in adjacent activated sludge tanks.

The BIO-DENIPHO and BIO-DENITRO processes, which can be applied in any type of reactors, are very flexible. The former enables removal of nitrogen from the wastewater and the latter nitrogen as well as phosphorus.

The BIO-DENITRO process comprises two identical activated sludge tanks and a settling tank. The activated sludge tanks, fitted with aeration and agitation devices, are interconnected and operate alternately, but with continuous feed and discharge of wastewater.

The wastewater to be treated arrives through a distribution chamber and is introduced into one of the tanks. The treatment is achieved by repeating one sequence which includes two main phases, A and B:

in phase A, the untreated water is introduced into the first anoxic tank, from where the nitrates accumulated during the previous phase are removed. The mixed liquor passes into the second tank which operates under aerobic conditions to enable nitrification and elimination of organic pollutants.

during phase B, the water is admitted to the second tank, and the denitrification and nitrification phases are inverted compared to phase A.

Sludge from the settling tank is mainly recirculated upstream of the biological treatment unit in order to maintain a consistent concentration of the purifying biomass. The surplus is removed for further treatment.

The BIO-DENIPHO process, in which also phosphorus is removed, is an extension of BIO-DENITRO. An anaerobic tank has been inserted as the first stage to which the return sludge and wastewater are fed. As the biomass is exposed to alternating anaerobic and oxic conditions, the growth of certain micro-organisms capable of taking up and storing excess phosphorus during the aerobic periods will be enhanced. The phosphorus is then removed with the surplus sludge.