Aerated lagoons 2.0

September 30, 2021

Wastewater treatment helps to significantly reduce pollutants generated by human activity discharged into the environment. Several technologies are available to municipalities who must make their selection according to water flow, pollutant concentrations to be treated, available space, capacity of the receiving environment and other criteria required by the authorities.

Applicable regulation requirements in effect in Québec define obligations for organic pollutants, suspended solids, pH and toxicity. For stations discharging over 2,500 m3/d, the toxicity level must be verified periodically with laboratory tests. For smaller stations, although the toxicity measure is not particularly specified, respect of the requirements is still required. In domestic type wastewaters, this toxicity is linked for the most part to the ammoniacal nitrogen concentration, which makes it an interesting pollutant.

Ammoniacal nitrogen removal, also called "nitrification", depends on multiple factors, namely the water temperature. In a cold climate such as ours, aerated lagoons, which represent the majority of wastewater treatment plants in Québec, are not very efficient for nitrification and several could not fully respect toxicity requirements should measurements be taken. In a time where several aerated lagoons near their design capacity, it appears wise to consider ammoniacal nitrogen removal processes towards a potential upgrade.

Bionest KAMAK system is thus a unique option to be considered. This system contains five zones, two biological fixed film reactors, which increase the aerated lagoons’ capacity while being installed within the existing lagoons and which also reduces the costs of civil engineering. This is called a hybrid process where a biofilm forms inside the biological reactors which increases the solids retention time, the biomass concentration and improves its distribution within the treatment volume.

This solution, without enlarging the footprint or work load of operators, increases not only the treatment capacity, but also allocates a nitrification of over 90 % throughout the year.

Recent results in real conditions show that the KAMAK enabled nitrification during the winter, where water temperature was below 1 degree C and remained under 5 degrees C for close to four months, with performances above requirements for other regulated parameters.