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A CLEAR future

Thirty six years after the passage of the Clean Water Act public water utilities are still using the same methods and technologies to treat domestic sewage as they did in 1972. Conventional technology involves initial screening for the removal of large solids followed by some means of biological treatment for the reduction of organic matter and the conversion of ammonia and organic nitrogen to nitrate. After the bacteria (bugs) have performed their functions they are separated from the wastewater and then returned to the beginning of the process to start their work all over again. The clarified wastewater is then disinfected and discharged to a stream or river. As a result of a recent round of lawsuits by the Sierra Club, the Chesapeake Bay Foundation and several other environmental groups, the US Supreme Count ordered the EPA to step up its enforcement against polluters and in particular against municipal wastewater treatment plants. In response, the EPA ordered the States of Maryland and Virginia to require all treatment plants tributary to the Chesapeake Bay to reduce the nutrients nitrate and phosphorous to “limits of technology” by December 31, 2010 or face serious fines. Presently most municipal wastewater plants discharge nitrates at concentrations ranging between 8 - 18 milligrams per liter (mg/l) and phosphorous at concentrations between 3 - 6 mg/l. EPA’s expectations for the newly prescribed “limits of technology” will result in more stringent discharge levels of nitrate and phosphorous to 3.0 mg/l and 0.3 mg/l respectively. The Rigby Process effectively reduces both nitrates and phosphorous to concentrations below 0.2 mg/l.

Besides municipal wastewater treatment plants there are numerous other sources of wastewater that require treatment prior to disposal. Almost every single family home not connected to a public sewer disposes of its sewage through a septic system. Remotely located campgrounds, schools and inns and such commercial field activities as oil and natural gas exploration and mining operations all have special wastewater treatment and disposal needs. Further, petroleum contaminated runoff from gas stations and parking lots and combined (sanitary and stormwater) sewer overflows all cause degradation to the environment. Even such unique activities as military, merchant, pleasure and cruise ship operations and missions to space require treatment of sanitary wastewater. It was recently reported that NASA spent $250 million to develop a new wastewater treatment system for the Space Shuttle with the capability of producing treated water which can be reused for human consumption.

The construction and operation of conventional treatment systems comes with numerous costly problems. Due to the shear size and complexity of the facilities, conventional treatment systems are costly to build. A normal hydraulic retention time in a conventional wastewater treatment plant is twenty-four hours. As byproducts of both biological and chemical treatment, large volumes of waste sludge are produced and disposed of in landfills. Energy usage in a conventional plant is excessive requiring the operation of large horsepower motors and generators to run aeration blower, pumps, valves, lights and control systems. Conventional treatment plants require large areas of land and many support facilities such as filter press buildings, sludge storage tanks, chemical silos, analytical buildings, maintenance shops, parking lots, etc. Conventional systems typically produce foul odors and require trained operators and mechanics. Also, since conventional plants rely on bacteria for the reduction and removal of organics and nutrients, they are always subject to the risk of toxic shocks which can kill the bacteria and render the plant ineffective. Finally, because conventional systems use biological methods for treatment, the final plant effluent must always be disinfected with chlorine or ultra-violet (UV) light to kill harmful bacteria.

Existing Treatment Technology