Reduction of pathogens, indicator bacteria, and alternative indicators by wastewater treatment and reclamation processes

The need for alternative sources of water, especially for non-potable purposes, has been met in many states in the US and throughout the world through the use of reclaimed wastewater. Wastewater contains a wide variety of microbial pathogens that may pose a risk to human health if not properly controlled; however, there are currently no national standards for microorganisms or consistent treatment requirements in the US with regards to reclaimed water. Besides the routine monitoring for TC and FC bacteria that has been used for assessing water quality, several types of alternative microorganisms have been suggested as indicators of water quality, fecal pollution, and public health risks. These include enterococci, Clostridium perfringens, and coliphage among others. This project evaluated the removal of both indicators (TC and FC, enterococci, C. perfringens and coliphage) and pathogens (enteroviruses, Giardia spp. and Cryptosporidium spp.) at 3 water reclamation facilities with varying treatment designs and operations. The facilities evaluated range in size from 20 to 44 million Liters per day capacity, with both shallow and deep bed sand/anthracite filters. Differences also existed in the disinfection processes for the 3 reclamation plants. The TC and FC showed a 5 to 7 log reduction throughout the treatment processes with no detectable levels in the final effluent. However, even though the alternative indicators (enterococci, C. perfringens and coliphage) showed reductions that varied from 2 to 6 logs, some levels of these indicators were consistently detected in 2 of the 3 facilities in the final reclaimed effluent. Both Cryptosporidium spp. and Giardia spp. were detected in the final effluent in all 3 facilities, even when no indicators were present. Virus detection was seasonal, and associated with cooler temperatures and less disinfection. The results of this study indicate that differences in filter design, operations, and disinfection approaches were responsible for differences in inter and intra facility water quality variability.