Sewage wastes can attract insects and rodents; encourage the growth of disease causing bacteria and pollute the environment. Therefore, proper disposal of sewage wastes is an essential part of health protection and disease prevention. If you live in an area where a public sewage disposal system is not available, the responsibility for proper disposal rests with you.

How does a septic tank/treatment plant work?

A typical sewage disposal system has two basic parts:

  1. A septic tank, or a package treatment plant, or an engineer-designed treatment plant, or a combination of these, and
  2. an appropriate disposal area - usually a series of underground pipes with holes in them, that let treated liquid from the septic tank soak into the ground below the surface.  

Septic tank: A septic tank is a watertight, underground container for receiving, treating, and settling human wastes. The solids settle to the bottom of the tank and become sludge, while oils and other light material float to the surface, forming a scum layer. Within the tank, anaerobic bacteria (bacteria that do not need oxygen) break down the solid wastes. When the septic tank is working properly, these bacteria can reduce the solids by 50 or 60 per cent. The liquid between the sludge on the bottom of the tank and the scum on the top flows out of the tank into the disposal area, where further breakdown occurs within the soil, until the liquid effluent is harmless and inert. The sludge and surface oils remaining in the septic tank need to be pumped out regularly. This must be done by registered onsite wastewater practitioner (ROWP) or other authorized person. If you do not maintain your sewage disposal system properly, this can result in the premature failure of your system, and you will need to pay for costly repairs or replacement of your disposal area.

Treatment Plant: A typical treatment plant uses air to help break down the wastes. In some cases, the wastes are treated in a septic tank first, before they flow into the treatment plant. Other treatment plants may be multi-chambered, and not need any pre-settling of solid wastes. A treatment plant is used to treat liquid wastes to a higher quality, so it is cleaner and safer before it enters the disposal area than discharge from a regular septic tank. The net result for the homeowner is a smaller disposal area. However, because these treatment plants are more complex than septic tanks, with various working parts, they need more maintenance to make sure they work properly.