Cochrane Septic
RESEARCH PAPER
Courtesy of "ROCKYVIEW AQUA LTD" And "COCHRANE SEPTIC". Your Rockyview Resident Specialist.
HOW SOIL TREATS SEPTIC TANK EFFLUENT
Suitable soil is an effective medium for septic tank effluent. Soil contains a complex biological community, one tablespoon of soil contains over one million microscopic organisms, including bacteria, protozoa, molds and other critters. It is the bacteria and other organisms in the soil that treat the waste water and purify it before it reaches the groundwater table. Waste water must pass through the soil slowly enough to provide contact time with soil particles and micro-organisms.
WHAT IS WASTE WATER (EFFLUENT)?
Waste water, which enters the soil in a septic treatment system, becomes food and water for the biological community. Normally the waste water leaving the septic tank is 99.9% water and only .1% pollutants (solids) that need to be removed. The percentage of solids in the waste water will be dramatically higher than .1% if the septic tank is not being cleaned at the proper frequency and thus overloading the field. The normal .1% solids in waste water that must be removed or modified consists mostly of organic material, bacteria and nutrients. The organic material comes from food preparation, dish and clothes washing, and wastes from the relatively inefficient human digestive system. Pathogens are micro-organisms that cause disease and are usually present in residential sewage. Fecal coliforms are indicators of the presence of pathogens. Along with these coliforms are two septic system nutrients, nitrogen and phosphorus which are of major concern in septic tank effluent.
NITRATE REMOVAL
Nitrogen from the septic tank is usually in the ammonia form. While some is used by the soil bacteria, most is converted to nitrate in the aerated soil. Nitrates are soluble and will move with soil water. Nitrate movement is one of the reasons for separation distances between septic treatment systems and water supply wells. Although a properly located and installed septic field does an excellent job of reducing Nitrate load by denitrification, there remains the possibility of nitrate problems with water supply wells.
PHOSPHATE REMOVAL
Phosphates are removed from waste water by being absorbed into soil particles, particularly particles with high concentrations of iron manganese and aluminum. Soils with a great percentage of clay particles have more of these minerals than sand. Phosphates move through the soil at t rate of 10 to 20 inches per year. If a septic system is functioning properly, problems of phosphate movement from the sptic field to groundwaters should be minimal.
SOIL AS A SELF-RENEWING TREATMENT SYSTEM
Soil of suitable texture is an excellent treatment medium for septic tank effluent. The soil is a self-renewing treatment system and will maintain ths treatment effectiveness and capacity only if the septic tank effluent remains of reasonable quality and as long as aerobic conditions exist in the soil treatment system. A properly installed and maintained septic field receiving good quality effluent (grey water) can be reasonably expected to have a life expectancy of 30 to 50 years while a field receiving a high percentage of sludge many not last ten years.