Related by context. Frequent words. (Click for all words.) 73 nitrate 61 arsenic 59 selenium 58 phosphorus 57 phosphorous 56 contaminants 55 contaminant 54 perchlorate 54 groundwater 53 chromium 52 pollutants 52 dioxins 52 coliform bacteria 52 sulfate 52 toxins 51 chloride 51 E. coli bacteria 51 mercury 51 effluent 51 toxin 51 pesticides 50 chemicals 50 phosphates 50 turbidity 50 fecal coliform 50 sodium chloride 49 sulfates 49 fluoride 49 bacterial contamination 49 toxic chemicals 49 toxic substances 49 estrogens 49 radium 49 hexavalent chromium 49 hydrogen sulfide 48 harmful chemicals 48 sodium 48 nitrite 48 dioxin 48 VOCs 48 chlorine 48 nitrogen 48 ammonia 48 nitroglycerin 48 coliform 48 methylmercury 47 potassium 47 calcium 47 volatile organic compounds 47 milligrams 47 nutrients 47 septic systems 47 triclosan 47 salts 47 concentrations 47 carcinogens 46 potentially harmful 46 ppb 46 aquifer 46 trace amounts 46 nutrient 46 substances 46 uric acid 46 E. coli 46 aquifers 45 thyroid hormone 45 chlorination 45 tritium 45 manganese 45 contaminated 45 benzene 45 iodine 45 naturally occurring 45 mercury contamination 45 methane 45 sibutramine 45 pH 45 pollutant 45 contamination 44 sulfur dioxide 44 Sodium 44 dissolved oxygen 44 suspended solids 44 bacteria 44 particulate matter 44 groundwater contamination 44 septic tanks 44 biosolids 44 salinity 44 vitamin B# 44 polychlorinated biphenyls 44 algae blooms 44 particulates 44 Nutrients 44 Arsenic 44 phosphate 44 sediment 44 barium 44 harmful substances 44 acrylamide 44 hazardous chemicals