Background Drip irrigation has been around for over 25 years. In Hawaii, over 100,000 acres of sugar cane and pineapple are subsurface drip irrigated. Drip irrigation of sugar cane in Hawaii was first initiated in March 1970 on an 8,000 square foot plot at the HSPA's Kunia Experiment Station. In Hawaii, the primary components of the effluent wastewater subsurface drip irrigation system are the supply lines, the filtration station and automation controls, disinfection system, main lines, sub-mains, and the polyethylene lateral drip tubing with water discharging emitter devices. The emitter devices are engineered products calibrated and manufactured to provide specific uniform flow rates at specific pressures.
Supply lines transport the effluent from the wastewater treatment plant to the filter station.
The filter station, the heart of the system, consists of sand media type pressure filters, flow meters and sensors, and automatic valves and controls to effectively manage and monitor the subsurface drip irrigation system. Chlorine, the primary disinfectant used to preclude biofouling of the drip tube emitters, is injected at the filter station. The main lines transport the filtered and treated effluent from the filter station to various irrigation blocks that are controlled by automatic valves. Sub-mains within these irrigation blocks further distribute the treated effluent to individual drip tube laterals. The drip tube laterals uniformly distribute and emit the effluent using capillary action in the soil for distribution into the plant root zones.