Reduce Wet Well Cleaning Cost At Wastewater Pumping Stations

The wastewater collection system in the City of Edmonton, Alberta, Canada includes sixty-three wastewater pumping stations. Some of the stations were built in the nineteen thirties and the depths of the wet wells may vary from 3.5 metres to 20 metres, (11′ to 65′). Regular cleaning of wet wells is a common activity performed by collection system personnel. The frequency of cleaning the wet wells may depend on several factors including amount of inflow, configuration, size, pumping capacity and inflow characteristics. The accumulation of grease, rags, hair, paper and other floatable solids combine to form a solid floating mass at the surface. At the same time, non-floatable solids settle and consolidate at the bottom of the wet well. The colder temperatures due to the northern climate in Edmonton cause the grease and oils in the wastewater to coagulate and form semi-solid floating masses that result in deposits on the walls of the wet well. If left unattended the floating mass at the surface will interfere with the normal functioning of level control equipment and eventually cause pumping difficulties. The heavy solids accumulate on the floor of the in the wet well and encourage the development of hydrogen sulfide and associated odors. These odors become extremely intense when the sediment is disturbed during cleaning activities.