Method and device to optimize plug flow in an aerobic biological wastewater treatment reactor

A method for the treatment of wastewater in a biological treatment reactor, comprising the steps of:

• (a) introducing wastewater influent at the bottom part of the reactor while simultaneously decanting treated wastewater effluent at the operational water level in the top part of the reactor, wherein the biological treatment reactor comprises biomass;
• (b) an aeration step;
• and
• (c) a settling step wherein the biomass is allowed to settle;
• wherein step (a) is performed under vertical plug flow conditions achieved by introducing the wastewater influent into the reactor through an influent distributor system comprising two or more distributor pipes, said two or more pipes comprising one or more nozzle outlets arranged to provide an equal distribution of influent wastewater across the reactor bottom surface, and discharging the treated wastewater effluent through an effluent decanter system configured to discharge the treated wastewater effluent equally across the operational water level in the top part of the reactor;
• and
• wherein during step (a) the equal distribution of the influent wastewater across the distributor pipes and/or the degree of plug-flow in the reactor is monitored, and when a suboptimal distribution or a suboptimal degree of plug-flow is detected the influent distributor system and/or effluent decanter system is cleaned by removing fouling and/or blockage.