"Infrastructure on a Skid"


On-Site Utilities Package Systems

Description Matched transportable skid-mounted modules providing a complete on-site wastewater treatment solution (including flush toilet, disinfected secondary quality effluent suitable for surface discharge); and clean, reliable, utility-quality (or better) electric power for single family residences in locations lacking such infrastructure and/or where it is not feasible to extend existing utilities to the site.

The complete package consists of two 4' x 8' insulated enclosures, one containing graywater and toilet waste treatment modules; the other, a small diesel generator with high efficiency heat recovery, electric energy storage (batteries), sine wave inverter, thermal energy storage (water tank), radiant panel hydronic heat distribution system, and a "smart", integrated control system designed to maximize energy efficiency and reliability. Provision is also included for integration of alternative sources of power (e.g. wind, micro-hydro, solar) where available.

The complete package will provide a flush toilet sanitation system and all heating and power requirements for a 1,000 sq. ft, well-insulated house with energy efficient lighting and appliances. Estimated installed cost, including one toilet, sewage lift station and required site work will range between $30,000 and $50,000 depending on site-specific requirements.

Estimated overall fuel utilization efficiency is approximately 75% (as compared to 25% for typical diesel electric installations - or 50-60% for typical diesel electric installations with heat recovery). Preliminary calculations indicate that total real operating costs, (including allowances for normal maintenance, repair & replacement costs) can be significantly less than current subsidized costs in typical rural village installations.

Waste Treatment Systems The waste treatment module includes an anaerobic digester for treating toilet wastes, a biofilter for treating graywater (and treated digester effluent), and a 'smart' electronic controller capable of providing advanced system diagnostics as well as normal monitoring and control functions.

Toilet wastes from low water use (1-1/2 pint/flush) toilets are pumped into a
90 gallon digester. (This is the smallest basic module, nominally sized for a family of 6, but the design is completely scalable. An easy to use, interactive on-line system sizing and design tool allows end users to determine preliminary size and cost requirements). Treated effluent from the digester flows into the biofilter, where it is mixed with (and diluted by) incoming graywater at about a 30:1 ratio.

The biofilter is sized to treat up to 200 gallons/day of graywater, providing advanced (secondary or better) quality effluent, while using only 20 watts of electricity. It is a simple, low cost unit built into a commonly available, off-the-shelf, closed head 35" diameter x 78" high polyethylene tank partitioned into two chambers: a surge tank above, treatment section below.

The surge tank -- and a simple airlift pump -- provide flow equalization. The lower (treatment) section includes both aerobic and aerobic components, each providing different functions. The regulated ultra-low flow rates maintained by the airlift pump allow a thick sludge blanket to develop, through which incoming wastes are filtered -- effectively providing all the advantages of a fixed film system, but without the associated costs. Aeration is provided by an air-driven rotating biological contactor (RBC). Effluent disinfection is provided by an ozone generator.

The 'smart' controller differs from conventional controllers in that, not only does it perform normal monitoring and control functions, but it also includes routines designed to anticipate when a level switch or pump (for example) should open or close, turn on or off, outputting appropriate "maintenance due" signals if it doesn't happen as expected. Alarms and warnings are output to LED's on the face of the unit, and, optionally, can be output to a telephone dialer which can be programmed to automatically dial up and signal local (and/or remote) maintenance personnel of alarm or maintenance due conditions. Different DTMF codes (telephone tones) are transmitted, corresponding to different conditions. DTMF codes provide a simple, robust signal which can be interpreted both by humans and/or remote alarm equipment.

Lack of maintenance is probably the single most important factor contributing to the failure of on site wastewater treatment systems. The probability that routine preventive maintenance will be performed can be greatly increased by (1) making it easy to do, and (2) providing advance warning -- i.e. before problems occur -- that it needs to be done.

Power/Heat Systems The power/heat module contains a liquid-cooled diesel electric generator, battery bank, sine wave inverter, hot water storage tank, radiant panel hydronic heat distribution system, heat recovery equipment (for both engine jacket and exhaust), and an integrated electronic control system designed to maximize energy efficiency and reliability.

The gen-set is sized to provide the minimum daily amount of electricity, rather than sized for peak demand as is normally done. Daily load for a house well-equipped with all high-efficiency appliances (e.g. 'Sunfrost' freezer & refrigerator, etc) and lighting (e.g. compact fluorescents), can be less than 24 KW/day without sacrifice. A 10 KW prime power generator operated at 3/4 load (for maximum efficiency and longevity) can serve the load, operating less than 4 hours/day. Ample battery storage capacity and a generously sized full sine wave inverter provide storage for off-peak usage and required capacity for surges and peak power demand.

Preliminary calculations indicate that recovered waste heat from the generator can provide the majority of the total annual heating energy requirements of a well insulated, efficient 1,000 s.f. house in interior Alaska. A small space heater (e.g. woodstove, Monitor or Toyostove) can be used to provide supplemental heat on design heating days. Excess heat -- above the instantaneous demand -- generated by the generator when it is running is stored in a water tank (thermal energy storage 'battery'). A low temperature radiant floor panel hydronic heating system is provided, to take maximum advantage of available storage tank temperatures.

Systems Integration, Efficiency All components are tightly integrated, providing 'whole system' efficiencies not available in individually designed separate systems.

Conventional on-site power systems are normally sized for peak demand, then operated far below their peak efficiency. Conventional wisdom also does not normally deem it cost-effective to recover heat from small on-site systems. Both assumptions view each of the systems in isolation, rather than viewing all of the components (including the house) as parts of an integrated whole.

By providing both ample thermal and electric storage capacity, and properly sized distribution equipment (i.e. inverter and radiant panel hydronic heating system), the gen-set can be much smaller and operated at peak efficiency, rather than sized to handle peak loads and then operated at low efficiency.

When the concept is extended out to an entire rural village (one that must import and store all of it's heating fuel...) the potential impact of doubling or tripling the overall utilization efficiency of that fuel may be dramatic.


AutoCAD (.dwf) drawings (require Autodesk DWF Viewer, available for free from Autodesk)

Biorealis Systems, Inc., P.O. Box 1145, Willow, AK 99688 support@biorealis.com
This page, and all contents, are Copyright (C) 1998-2010 by Biorealis Systems, Inc., Willow, U.S.A. 

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