title: Appropriate preservation of dairy wastewater samples for environmental analysis.
abstract: Thousands of gallons of water are used in dairies to wash cows before milking and for cleaning equipment. The wastewater generated contains elevated levels of organic matter and pollutants, including nitrogen that once converted, may contaminate groundwater with nitrate. This study was conducted to determine the amount of sulfuric acid needed to preserve wastewater samples from a New Mexico dairy in the southwestern U.S. Titrations of wastewater from a local dairy using full strength (18 M) sulfuric acid were performed to determine the amount of acid needed to bring the pH of the sample to below two, the recommended pH for sample preservation. An average of 0.33 mL of acid was required for every 100 mL of wastewater. Due to sample variability, we recommend that 0.4 mL sulfuric acid be added for every 100 mL dairy wastewater sample to ensure adequate acidification. This quantity is twice the amount currently recommended in U.S. Environmental Protection Agency guidelines.
authors.affiliation: New Mexico State University, Department of Agronomy and Horticulture, Las Cruces, New Mexico, USA. aulery@nmsu.edu
authors.forename: April L
authors.initials: AL
authors.lastname: Ulery
authors.forename: Robert
authors.initials: R
authors.lastname: Flynn
authors.forename: Ramona
authors.initials: R
authors.lastname: Parra
mesh_terms: D003612:Dairying; D004784:Environmental Monitoring / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D009516:New Mexico; D014481:United States; D014484:United States Environmental Protection Agency; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D007220:Industrial Waste; D014874:Water Pollutants, Chemical