Rapid Sand Infiltration System Design and Evaluation
Banner completed a hydrological and engineering assessment of an existing wastewater treatment system that allowed AEP to formally accept the conversion of the existing wastewater stabilization pond into a hybrid rapid sand infiltration system for a small Village located in Northern Alberta. The Village was instructed to evaluate their sewage treatment system because it has been in operation for over 44 years without an upgrade. Wastewater stabilization systems used today in Alberta are generally very cost effective however these systems can be very expensive if unsuitable subsoil conditions exist in the local area. The soil conditions in close proximity to the Village were unsuitable indicating that a synthetic liner would be required, or the importation of suitable soil material from many miles away would be necessary, both very costly alternatives. Hence, an alternative solution was needed to reduce a terrible financial burden for the Village. Banner proposed the concept of converting the existing sewage lagoon system into a rapid sand infiltration system by providing suitable pre-treatment of the municipal wastewater prior to discharge into the lagoon. In this manner, the percolation of the treated wastewater from the lagoon into the surrounding groundwater could be considered an acceptable method for the disposal of wastewater by AEP, provided certain parameters were controlled and monitored during treatment. The draft report summarizing the design recommendations and the Banner risk assessment was submitted to AEP for consideration on Oct 21, 2002. The formal risk assessment involving Banner, the Village of Edgerton, AEP and AT&U was completed during the week of Nov 28, 2002. During this risk assessment, the key stakeholders of the project collectively discussed and evaluated the findings of the study and concluded that the recommendations would be accepted pending the submission of the final report. Minor alterations and/or additions were required.
The design recommendations of the study are based upon proven technology, which Banner strategically used for the benefit of its clients. The capital cost reductions are in the order of 90% based upon the original engineered estimates (about 2.2 Million in savings). The study verified that the current system provides both satisfactory treatment and capacity, and that no major upgrade or expansion of the system is required for a long time. Both the client and AEP support of this innovative engineering approach and the plant represents the only approved "hybrid rapid sand infiltration" project in Northern Alberta.