DECENTRALIZED WASTEWATER CLUSTER MANAGEMENT: OPERATION AND MAINTENANCE EXPERIENCE AND COSTS

In Mobile, Alabama, 12 public utility-managed decentralized wastewater cluster systems have been implemented over the past four and one-half years. New suburban development is pushing west from the city, into unsewered watersheds, including the watershed containing J.B. Converse Reservoir, the city's drinking water source. Traditionally, wastewater management in these developing areas has consisted of traditional onsite treatment (septic tanks and dispersal fields), but with new land-development pressure, the developers desire for more marketable (sewered) properties, and some history of onsite system failures, decentralized cluster systems serving 90 to 270 homes each have been implemented by three separate utilities. The decentralized cluster systems consist of small-diameter effluent sewer (septic tank effluent pump (STEP) or gravity (STEG) collection), recirculating packed bed treatment, and in-ground effluent dispersal or reuse. The management models being used in Mobile are most closely aligned with EPA's management level 5—utility ownership and maintenance of the entire system. Financing of the systems total capital cost (7500–8000 per home) consists of some form of developer participation in up-front costs (equity investment and/or tap fees) and capital recovery from sewer fees. Individual homeowners pay a 35–40 per month sewer fee for comprehensive sewer service. To date, the operation of these small-diameter effluent sewers and packed bed treatment systems has been quite efficient and maintenance activity minimal. Operation and maintenance costs for cluster systems serving 100 homes range from 8000 to 15,000 per year.