Transcript Document
Water Services National Training Group and National Federation of Group Water Schemes 7th Annual Rural Water Services Conference 18th September 2008 “Septic Tank Effluent Drainage System” STEDS (Update) Jim McGuire Senior Engineer North Tipperary County Council Background Project description Current status Experience /Identified Issues Alternative wastewater treatment systems for small rural communities The Challenge: Sustainability Ease of Maintenance Robust performance Process performance Low energy costs Low operating costs Approach Literature search Short list of options Real life applications Pilot Project PROJECT TEAM Treatment System: Orenco, USA Consulting Engineers: Nicholas ODwyer &Partners Contractor: EPS, Mallow, Co. Cork Client: Funding providing by: North Tiperary County Council Water Services National Training Group Department of Environment , Heritage and Local Government STEDS Components Fibreglass Tank in each Garden Primary treatment in interceptor tanks 1000- or 1500-gallon tank per residence 70% removal of fats, oils, and greases 24-hour emergency storage 12-year pumpout with 95% confidence Abuses stay in interceptor tank Chemical sources easier to identify Components, cont. • Pump vault • High-head effluent pump • Filter cartridge • Float assembly • Discharge assembly Collection System Shallow burial depth Laid to contour of land No minimum velocities No oversized designs Low operation and maintenance costs Secondary Treatment Packed bed filter Engineered textile material Complete, premanufactured package Operates in an unsaturated condition (not submerged) Uses filtration and biological/chemical reduction Advantages Flexible in design Adaptable to varying site conditions Allows for phased development, modular Can be integrated into existing sewer infrastructure? Can be integrated into existing treatment system Design includes storage/reserve in the event of power outages or need to repair mainline break Low-impact construction Minimal disruption to community Advantages Cost-effectiveness Low initial costs? No manholes No pumping stations Low operating costs Low maintenance costs Low and gradual repair/replacement costs Benefits May allow the construction of houses in areas where standard sewers or septic tank systems cannot be used Has affordable installation costs and low maintenance costs Has little visual impact Experience 1. Retrofit Challenge • No rain water can enter system • No ground water can enter system Experience 2. Sampling Challenge • Low flows pose particular challenges • Various arrangements tried Householders Play an Important Role Experience 3. Householders Role • No bleaches • No discharges from water softeners • No under sink macerators • Minimise phosphates in detergents COSTS 29 Houses served Cost outturn not finalised (€850,000 excl. VAT) Includes range of non typical items Non typical costs Overseas manufacture / Shipping Retrofit project Reconfiguration of existing connections Ground conditions Telemetry/data capture Sampling/monitoring Additional connections Additional single unit treatment system Alternative wastewater treatment systems for small rural communities The Challenge: Sustainability Ease of Maintenance Robust performance Process performance Low energy costs Low operating costs Conclusions • • • • Retrofit/rainwater challenges overcome Sampling challenges resolved Operating procedures improved Final judgement awaited • Further Close monitoring • Performance is positive • Phosphates End Water Services National Training Group and National Federation of Group Water Schemes 7th Annual Rural Water Services Conference 18th September 2008