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HIGH PERFORMANCE DEVICES FOR SEPTIC SYTEMS
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 701P0104, . (doi: 10.13031/2013.15789)Authors: Y. Berube, R. Lacasse and N. Viel
Keywords: Septic tank, inlet device, outlet device, flow regulation, gravity flow divider, hydraulic event, BOD, suspended solids
In order to improve the performance of septic systems, especially at retaining suspended solids in septic tank which foul downstream secondary treatment systems, the writers have developed novel inlet and outlet devices with damping effects on hydraulic events and a reliable pulsing flow divider (PFD) for even distribution of tank effluent. Using tap water or salt water with suspended polystyrene (PS) beads, we measured solids retention inside the test tank, water outflow as a function of tank water level and regulation of water outflow in response to 100L hydraulic events. Using domestic wastewater (BOD5 200 mg/L; SS = 100 mg/L), we measured uniformity of flow distribution. The novel inlet device provided a 50-fold increase over conventional device performance in tank retention of beads. With the 2 novel outlet devices, tank outflow was independent of water level up to 75 mm above the outlet invert and also spread the hydraulic events very evenly over a 50 minute period at 2 L/min and eliminated the outflow peak of 30 L/min. The PFD consistently divided domestic wastewater outflow into 2 to 8 streams with less than 10% variation in flow rate. Tests also showed reliable and consistent operation of the novel outlet and PFD prototypes under field conditions for at least nine months. The novel devices may offer major improvements in septic tank performance and reductions in the incidence of environmental contamination events and premature fouling of secondary treatment systems.
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