The environmental benefit of a community system is that it is operated by a certified sewer treatment operator, same as at a municipal plant. The main difference with a community plant is that the very clean effluent water is applied to the soil instead of being dumped back into the drinking water supply. One of the by products of sewage treatment is phosphate. This is one of the chemicals that turns our lakes and rivers green from alga growth. Phosphate is created with both processes, municipal and community systems, but phosphate is non soil mobile, meaning it doesn't move in the soil. The soil binds up the phosphate until the trees or grass can take it up as fertilizer, that’s why the effluent is put in at shallow depths. The other benefit of applying the effluent to the soil is the benefit of the filtering aspects of the soil on leftover pharmaceuticals, like cancer drugs and birth control pills, etc. One last benefit is the fact that microbes clean the effluent in the soil continually, so the longer the effluent stays in the soil, the cleaner it is before entering into a stream or river.
The cost is generally much less with a community system. The pipe needed to get the sewage to the plant is the main savings. Large municipals sometimes referred to as sanitary sewer lines, must be installed on a set slope and run from manhole to manhole. The reason for this is the tendency for these lines to clog. Pressure sewer lines don’t have the same problem since the pressure from the pumps at each residence keeps the solids moving along. This is the solids that the septic tanks at the residences don’t filter out. In most cases a large tap fee is required to connect onto a municipal system. If you are in an area with a lot of rock or frequent changes in topography, the cost of traditional sewer lines can be cost prohibitive.
Drip tubing for effluent water
Soil as a filter
The smaller pressure PVC type line needed for a community system are much more affordable and less costly to maintain.