SR0033424_ENG DESIGNED PLAN - Laserfiche WebLink

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• Consistent trouble-free operation; low maintenance (e.g, annual service call recommended; on-site routine service time 1 hour t) • Ease of maintenance (components should be easily accessible and serviceable) • Low energy consumption • Adequate storage during power outages (normally 24 hours or more at typical flows) • Recoverable and expandable • Reliability in providing the level of treated water required to final dispersal treatment processes Packed bed filters are inherently well suited for small-scale wastewater systems. They meet and typically exceed the above-listed requirements, due to the design and operational features described below: The Role of Watertight Tanks Watertight septic tanks,which precede PBFs,provide several benefits: 1) Allow primary settling of solids so that the packed bed filter treats largely liquid waste, 2) In conjunction with programmable timer controls,modulate and buffer large and uneven inflow, and 3) Provide emergency storage during power outages or equipment breakdowns. In multiple-pass recirculating PBFs, the recirculation tank provides even more buffering capacity by diluting the incoming septic tank effluent with treated effluent, to mitigate the effects of organic shock loading. "Fail-safe" design—Most PBF designs do not allow completely untreated sewage to be released ► since,unlike passive gravity-in/gravity-out systems,wastewater must pass through the treatment media before discharger This feature also prevents deliberate attempts to disable the treatment system. With passive gravity-in/gravity-out suspended growth aerobic systems, it is not uncommon for users to i "unplug"their aeration system to lower their electrical bill. With typical packed bed filters, only the' filtrate is discharged, ensuring high effluent quality dispensed for final dispersal. Flow management—PBF systems with programmable timers in their control panels have the ability to detect excessive inflow caused by infiltration, leaky plumbing fixtures, or higher-than-normal water consumption by the user. This"flow management"provided by the programmable timer is a fundamental tool that allows operators to detect and diagnose problems that would otherwise go undetected until complete system failure. The programmable controllers also provide improved treatment through frequent"micro-dosing" of the PBF. Speed of startup—The startup capability of PBFs is generally unsurpassable. Since PBFs utilize mechanical filtration as a means of physically removing matter, they are able to achieve high levels of effluent quality within hours of startup. The textile filters evaluated under the testing protocols described earlier demonstrated the ability to remove more than 80%cBOD5 within the first day of operation, and TSS concentrations under 15 mg/L were measured. Low power requirements—Power costs are low because of the intermittent operation of small fractional horsepower pumps. A typical single-pass PBF for an average single family home only requires 4-12 kWh/mo. At the national average of 8 cents per kWh, the power cost ranges from 32 to NTP-FLT-TRS-1 Rev.1.1,111g2 Page 9 of 12