Turf irrigation in hawaii using r‐1 effluent: Microbial and chemical effects

Abstract

Secondary‐treated, filtered, and chlorinated effluent (R‐l quality) blended with potable water was used for turf grass irrigation at the Hawaii Kai Golf Course on the island of Oahu, Hawaii. Blending was required because of the salinity level in the R‐l effluent. For control, only potable water was used for irrigation. Irrigation amounts varied with time based upon rainfall. Suction lysimeters were installed at 25‐cm and 40‐cm depths to collect soil‐water samples. In addition, water samples from potable water and blended water storage impoundments were collected for analysis. All water samples were analyzed for nitrate, chemical oxygen demand, pH, conductivity, and fecal coliform bacteria density. Grass samples and soil samples were analyzed for fecal bacteria. Results indicated that fertilization of the turf affected the nitrate content of certain suction lysimeter samples. Conductivity of the leachate samples decreased with time, indicating possible dilution with rainwater. The most significant observation was the growth of fecal bacteria in leachate waters and open storage reservoirs. Grass and soil samples also showed the presence of fecal coliform bacteria. This indicates that fecal coliforms should not be used as indicator bacteria in tropical environments, where they are naturally present. For Oahu, using fecal coliforms as indicator bacteria can be a problem if R‐l effluent is used on areas overlying potable water aquifers. Clostridium perfringens, which is present in large numbers in wastewaters, may be a better indicator bacterium since it is not found in large numbers in the natural soil environment.