Some of the Benefits of Effluent Sewer Systems to Utilities

• Effluent sewer systems can be a source of profit to utilities.
• Effluent sewer systems reduce loads on overloaded conventional treatment systems.
• Permitting requirements are minimal.
• Effluent sewer systems efficiently accommodate seasonal population variations.
• Abuse of the system can be identified at the source.

1. Effluent sewer systems can be a source of profit to utilities. They allow utilities to add sewage service to their other services, expanding both their revenue base and their customer base. With each home paying a monthly fee, the utility can quickly recoup its investment because effluent sewer systems are cost-effective to install and maintain.

• Economical to install: Centralised systems use large-diameter lines and require expensive lift stations if there are hills between the homes and the treatment plant. These lines typically cost up to $150 per metre or more to install. In contrast, effluent sewer systems use small-diameter collection lines that follow the terrain and require less excavation; installation of these lines costs $15-20 per metre. Also, decentralised systems use natural processes in the septic tank and in the soil to treat wastes, whereas central treatment plants need power for pumping and aeration and space for large tanks.
• Economical to operate and maintain: A few contract or utility employees can operate and maintain a decentralised system serving hundreds of homes. The interceptor tank at each home or business needs to be pumped only once every 7–12 years at the most. The only mechanical component is a sturdy 1/2- or 3/4-hp pump (similar to a well pump) at each site, and the electricity to run it costs the homeowner less than $2 per month. A 1993 survey of effluent sewer projects in Oregon, Washington, and California showed that service calls averaged only 1.4 hours per month per 100 homes.

2. Effluent sewer systems reduce loads on overloaded conventional treatment systems. Treatment takes place in the interceptor tanks and in neighborhood treatment facilities instead of at the central plant. If effluent is piped to the central plant for treatment, it is of much higher quality than raw wastewater, placing less of a burden on the biological processes at the plant than raw sewage would. Digestion in each tank reduces the volume of solids that must be disposed of to as little as 10% of what it would be in a centralized sewer system. Finally, because effluent sewer systems are watertight, the system does not become overloaded when it rains.

3. Permitting requirements are minimal.  

4. Effluent sewer systems efficiently accommodate seasonal population variations. In areas where population varies by season, effluent sewer systems can accommodate seasonal loads without the expense of enlarging a centralised system.

5. Abuse of the system can be identified at the source. If a household or business dumps something bad down the drain, it will affect only its own tank, not the whole system. The cost of pumping and repairs can be charged to the homeowner.