Physical Description:

The graywater treatment unit (biofilter) is 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.

A "percolator pump" (simple airlift pump made from common PVC pipe and fittings and small air pump) installed in the surge tank slowly and continuously pumps water from the surge tank to the treatment section.

The lower (treatment) section contains a rotating biological contactor (RBC), and various baffles cut from 1/4" HDPE sheet material, to direct the flow of wastewater through it. The RBC is made entirely of non-corroding plastic materials. Shaft and bearings are made of UHMW. Media consists of sandwiched layers of corrugated PVC and polyolefin fiber disks providing exceptionally high surface-to-volume ratios. It is 75% submerged (reducing structural loading), and air-driven, powered by a small air pump similar to the percolator pump air pump described above.

Additional components include a small (< 3 watts) 12 VDC fan (not shown), and a power/control module (P/CM). The P/CM will include all of the power and control components, housed in a single NEMA 4X enclosure. Components include two air pumps (diaphragm type, 6 watts each), an ozone generator (corona discharge type, 2.5 watts), a DC to AC inverter (provides AC power required to operate the air pumps and ozone generator), a small (2" x 4") printed circuit board containing a programmable microcontroller and associated electronic components, and an air dryer (2" dia PVC tube filled with dessicant, for the ozone generator).

The P/CM is designed to be intrinsically safe, housed in a NEMA 4X enclosure, and requiring only a low- wattage 12 VDC power source. The microcontroller is the system "brain", controlling a solid state relay (SSR, for connecting to external feedpump in septic tank), as well as providing system diagnostics and alarms. Controller inputs will include status of level switches in the surge tank, holding tank feed pump status, and status of various internal timers and flags. Outputs will include a control signal to the SSR, various LED's on the face of the PC board, and an audible alarm. Serial I/O will also be provided, for communication with the outside world.

Functional Description:

Primary effluent (settled wastewater pumped from a holding tank, septic tank, or other source, depending on end use) enters the surge tank at the top. The surge tank provides flow equalization. Effective surge capacity is about 16 gallons. High and low level switches in the surge tank control a feed pump in the holding tank, dosing the surge tank about once every 2 hours.

The continuously running percolator pump slowly empties the surge tank, pumping water out of it into the lower section of the tank at an average flow rate of less than .14 gallons/ minute. At this rate it will take about 2 hours to empty the surge tank. Water pumped from the surge tank flows down through a passageway

(Zone 1 in the drawing) to the bottom of the tank. It then passes under a baffle and flows up through an "Upflow Anaerobic Sludge Blanket" (UASB, Zone 2), into the upper part of the tank, (Zone 3) which is well aerated and continuously stirred by a rotating biological contactor (RBC).

As the RBC rotates, the relatively high velocity of the rotating surfaces will cause the attached biofilm to shear off, continually re-exposing fresh layers underneath. The relatively large flocs sluffed from the RBC settle rapidly, accumulating to form the UASB (Zone 2) through which the incoming wastewater upflows. The majority of particulate BOD will be removed in this Zone 2, decomposing anaerobically. The majority of soluable BOD is removed in Zone 3. Depending on organic loading rate, it is expected that significant nitrification of ammonia will also occur in Zone 3 (i.e. at BOD < 30 mg/l, nitrogen oxidizing autotrophs can compete successfully with carbon-utilizing heterotrophs).

The UASB is maintained by sustaining a continuous low flow rate, rather than cycling a larger pump on and off. The percolator pump is a key component of the entire system, and one of the primary innovations: a very simple, inexpensive, very low energy pumping system capable of reliably maintaining the required continuous low flow rates without clogging or fouling. Peak upward flow velocity through the sludge blanket is less than 4" per hour, a barely perceptible ooze, as found in natural wetlands, and, more importantly, far lower than the settling velocity of the flocs.

A properly operated UASB will produce sludge with a granular structure. This granular sludge has a large surface area and good sedimentation properties, also containing diverse microbial populations. Weak agitation, and the granular structure are produced by an upward flow of gas-borne sludge through the blanket, in combination with the return downward flow of degassed sludge, which creates continuous convection insuring effective sludge to wastewater contact without the need for energy- consuming mechanical or hydraulic agitation.

From Zone 3, the wastewater flows over a weir, down and under a baffle and up through a final passage before passing through another fixed media block, and up into an ozone contact chamber. This high-surface-area media is made of PVC ribbon, functioning primarily as a final mechanical filter, and "permeable barrier" separating the highly agitated ozone contact chamber above from the relatively quiescent flow passage below.

The ozone generator and contact chamber will be sized to provide 1 mg/l with a contact time of 30 minutes -- exceeding minimum exposure levels required to achieve disinfection goals. Excess ozone is drawn over the top of the baffle back into Zone 3, across the exposed portion of the RBC (further contributing to available oxygen), and out a vent stack, by the small DC fan. This fan draws air from the surrounding space, providing oxygen to organisms attached to the RBC, as well as maintaining negative pressure in the tank, preventing odors from escaping to the surrounding space.

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. The Biorealis System 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.

Fixed media systems: Fixed media systems, characterized by high surface-to-volume ratios, offer significant advantages over conventional suspended media systems - open tanks with free-swimming organisms. Suspended media systems depend on long hydraulic retention times (i.e. large tank volume relative to flow rate) to allow time for solids to settle, and to prevent free-swimming organisms from being washed out faster than they reproduce. As such, they are particularly susceptible to upset by surges and uneven flowrates. In contrast, fixed media systems provide extensive surface area for organisms to adhere to, allowing higher hydraulic loading rates, and more organisms to be cultured in the same volume. Fixed media systems can therefore be smaller and/or be less susceptible to shock loading than suspended media systems of equal capacity -- offering significant opportunities to reduce cost and increase reliability.

Upflow Anaerobic Sludge Blanket (UASB): Upflow Anaerobic Sludge Blanket (UASB) methods were originally developed by a group at the Dutch Agriculture University of Wageningen in the late 60's. The Dutch beet sugar firm, CSM, then developed the basic technology to commercial application as they applied its use to solve their own waste treatment problems within several of their sugar factories. Since that time, the technology has been applied and adapted to a wide variety of waste treatment problems. Advantages over conventional aerobic methods typically include simplicity (no moving parts), low power consumption, reduced sludge volume, high loading rate, very small requirement for N, P, and micronutrients, and robustness (the biomass can survive for several months without any substrate and nutrient).^{[2] [3] [4] [5]}

Percolator Pump, Low flow rates, Maintenance Issues: Well-regulated stable flow control is absolutely critical to the proper operation of the Biorealis system. However, continuously maintaining such low flow rates in a wastewater environment, without frequent maintenance and/or use of expensive components has proven to be very difficult to accomplish - perhaps impossible with conventional liquid pumping systems and controls. Biofilm will accumulate on any and all surfaces in contact with wastewater, including the inside of pipes, pumps, inlet screens, etc. The problem with small liquid pumps sized for lower flow rates is that the small passages foul quickly, requiring frequent maintenance. The problem with pumps large enough to minimize fouling problems is that flow rates are too high, causing pumps to short-cycle, and/or preventing development of desired microbial growth patterns. Even the smallest pumps require level controls, timers and/or alarms for pump protection and proper dosing. Problems with control components have accounted for the majority of all system failures on previous systems. More reliable controls (i.e mil-spec, lab or industrial grade) are expensive, and incompatible with low-cost design goals.

In contrast, the percolator pump system is virtually maintenance free. The diaphragm air pump has no moving (i.e. rotating or subject to wear) parts. Turbulence created by air bubbles rising in the standpipe scrubs growth from the walls, reducing cleaning requirements. It is also less expensive and simpler. It can run dry indefinitely without damage - and with negligible energy use (i.e. 6 watts vs 60 watts for the smallest water pump) - completely eliminating the need for any controls. We have had a number of these pumps running continuously for over five years, without failure.

Air-driven Rotating Biological Contactor (RBC): A rotating biological contactor (RBC) is a media wheel designed to provide extended surface area for colonization by aerobic bacteria. The wheel is partially submerged and continuously rotated at about 1.5 RPM. As it turns, the microbial growth attached to the surfaces is alternately submerged and exposed to air. This provides a very effective method of getting oxygen to the attached microorganisms. To put the same amount of oxygen into the water with a fine bubble diffuser alone would require a compressor over 10 times larger.

BSI has experimented extensively with a variety of RBC designs, in an effort to develop a cost-effective, reliable device. The selected drive mechanism is similar to that of a water wheel, but instead of pumping water into upright vanes, the wheel is 75% submerged, and air from a bubble diffuser is released below inverted cups below the surface. This method improves greatly on earlier designs (i.e. various liquid pump-driven water wheels and motor-driven wheels). Advantages include reduced structural loading and consequent lighter weight and lower cost (it is almost neutral buoyancy), very low energy use (6 watts), and greatly improved maintenance-free reliability.

Diagnostics, Maintenance

One of the primary factors determining the ultimate value of any wastewater treatment system has to do, not with whether it works (most do), but how to keep it running, and what happens when it fails (and all will, sooner or later). An important part of this project is to develop and test a "smart" controller designed to significantly increase the long-term reliability of such systems. BSI has invested significant time and effort into developing such a controller. Following is a partial list (with notes & comments) of functions, that will provide insight into the proposed approach.

b. Commercial Applications:

Potential commercial applications for this technology include:

• Treatment and reclamation of septic tank effluent for secondary uses and/or to extend the life of failing drainfields.
• Production of potable water (With the addition of micro-filtration. Useful for remote/extreme environments, field camps, or emergency disaster relief situations.)
• Extending the life of existing centralized wastewater treatment facilities which are at or near capacity, by reducing organic loading at the source. Treated effluent is suitable for reuse, discharge to storm sewer, or groundwater recharge.
• Use with companion composting toilet to treat "compost tea". (Used together, each unit solves problems inherent to the other. The water treatment unit provides a way to deal with excess liquid in the composter, while liquid from the composter provides a regulated carbon source to the water treatment unit, beneficial to maintaining stable microbial populations. Sludge from the water treatment unit is added to the composter and converted to humus.)
• Emergency disaster relief. Compact, lightweight, easily transportable unit capable of producing effluent of quality suitable for surface discharge, while capable of operating on low-wattage alternative sources of energy.
• Affordable, user-maintainable on-site wastewater treatment for developing world or low-income rural applications (i.e. anywhere in the world currently lacking adequate sanitation facilities, and where money, clean water and energy are in short supply). Availability of component kits that can be installed in locally manufactured tanks (e.g. of concrete or clay) can reduce costs to end users dramatically.

c. Competitive Advantages:

The primary technical innovations of this design include:

• Development of a very simple, inexpensive, but robust pumped dosing system capable of maintaining a constant low flow rate through the system without fouling or maintenance,

• Use of the closely regulated fluid velocities thus achieved to, in effect, "grow" a fixed-film media system (sludge blanket) with exceptionally high biological contact surface area/volume at zero cost.

• Development of a simple air-driven rotating biological contactor (RBC) capable of providing high levels of aeration with very low energy input. (The design is the end result of 12 years of R&D and successive refinements, intended to solve reliability problems inherent to previous designs.)

• Development of an intelligent self-adapting controller capable of predicting potential failures before they occur, outputting appropriate preventive maintenance signals.

  Each innovation, by itself, is relatively insignificant. But taken together, and incorporated into a system that is (1) specifically designed to be manufactured in small local shops, and (2) developed in conjunction with an innovative manufacturing, marketing and distribution system designed to create and support a distributed network of such shops, it will yield synergistic results which may have dramatic impact, in terms of applications, performance, efficiencies and reduced cost.

  e. Commercialization:

  Primary design goals include (1) minimum cost to end-users, and (2) that the units should be able to be locally built using common tools and skills. These two goals go together. Under conventional product development methods, the combined costs of patent protection, product development, development of manufacturing capital plant, marketing, distribution and liability protection - and the cost of high-risk money required to pay for these items and return profits to investors - can exceed the basic cost of materials and labor by a considerable amount, typically doubling or even tripling the final cost, and limiting the potential market to the more affluent. We are not interested in developing yet another $5,000 package plant that requires a ¼ HP blower (i.e. more than 10 times the energy required by the Biorealis system) to operate. The market for such devices is already well populated.

  BSI's goal is to make the technology available and affordable to the broadest possible market. To that end, it is developing an innovative computer-integrated marketing, purchasing, order-taking, custom design, and distributed manufacturing system. An integral part of this effort will be a web site which will include decision making tools and a detailed input form where prospective buyers can enter their site-specific requirements and upload them to our server, where they will be linked to a parametric CAD model. The model is automatically updated to reflect the user's site- specific requirements, generating detailed custom shop drawings which will then be sent to a fabrication shop near the buyer.

  BSI intends to provide the tools necessary to develop and support a distributed network of such shops, including technical support, custom designs and detailed shop drawings (automated as described above), individual components (i.e. knocked down RBC's and P/CM's designed to be installed in locally built tanks made from locally available materials, etc.), complete kits, and/or fully assembled units ready to install - effectively "covering all bases". Our primary product is information. As access to rapidly emerging global information networks become a reality for more and more of the estimated three billion people on earth who could benefit most from these technologies, the engine and method described here could be a cost-effective way to deploy technologies currently unavailable to them.

  It is anticipated that if Phase I and Phase II R&D efforts prove the technical feasibility and commercialization potential of the Biorealis System, and if these units can then be cost-effectively produced using distributed manufacturing processes described above, we will have a clear winner, and follow-on development money will not be difficult to find. Another very significant advantage of the proposed commercialization methods, is that they are more "bottom-up" than "top-down", requiring correspondingly less "up-front" capitalization.