Dairy Wastewater

Introduction

The Dairy Industry is trending towards larger herds of cattle and smaller pastures, which is creating challenges in balancing nitrogen and phosphorus. The complex chemistry of the 13 forms of nitrogen (molecular nitrogen (N2), organic nitrogen (No), nitrites (NO¬2), nitrates (NO3), and other intermediate forms) make balancing the nitrogen cycle a challenge. Phosphorous has two general forms, organic (Po) and inorganic (Pi). There is a chemical imbalance between Po and Pi which results in excess Po being distributed on fields that cannot be utilized for pasture growth. The excess Po causes accumulation in the soil and leaches into waterways. Po is produced by the very feed given to ruminant animals; only ruminating animals can partially convert Po back to Pi. The growing shortage of Pi in the world illuminates the need for a solution.

A common aerobic process in dairy wastewater treatment is the lagoon system, which is usually paired with anaerobic digestion. This combination creates methane (CH4), ammonia (NH3), and hydrogen sulfide (H2S) as byproducts that burn to create sulfur dioxide (SO¬2), carbon dioxide (CO2), and nitrogen oxide (NOX). Most of this ammonia, which is toxic to fish and other animals, is transferred to the air then precipitates into rivers. Also, this whole system is costly and is being reviewed critically by the EPA for further regulations.

ACWT Process

  • Separates the bedding solids as 25% dry material from the manure, and uses Class A water for final rinsing of the bedding.
  • Screening through 2-mm screens will prepare the solution for the MBR process which includes aerobic aeration and 0.03-micron membrane ultra-filtration.
  • MBR technology with ultra-filtration which remove 99% of the pathogens will be incorporated to create Class B water
  • High intensity UV disinfection uses the Class B water to create Class A water that has 99.999999% pathogen removal.
  • All processes are aerobic, and manure wash down, after bedding is removed for reuse, will be pumped to aerobic MBR processing to allow further Po to Pi conversion.
  • Biosolids will be used as needed for field application or dewatered to 6% for reduced shipping cost to the offsite Class A 25% dry solids plant for further distribution to agriculture, preventing the overloading of nutrients on the dairy’s fields.

Benefits of ACWT Process

  • Eliminates the lagoons, all anaerobic storage, ammonia generation, and all manure handling by the dairy.
  • Eliminates the methane generation from anaerobic digestion, along with the hydrogen sulfide and ammonia discharging to the environment.
  • Eliminates the cost to scrub the hydrogen sulfide and ammonia from the anaerobic digestion in preparation for future regulations.
  • Saves the infrastructure cost and operation losses of electrical power generation from the corrosive, wet, and low BTU gases from the anaerobic digestion.
  • Saves the carbon in manure for reuse in the soil.
  • Recovers the nitrogen, phosphorus, and potassium at higher levels for reuse in the soil.
  • Stops the nitrogen and phosphorus run-offs into our rivers and estuaries.
  • Reduces the depletion and contamination of ground water.
  • Allows the proper application of nitrogen and phosphorus to the fields from the manure nutrients recovered, and relocates excess nutrients from the dairy as desired.
  • Stops the conversion of organic nitrogen to ammonia from using lagoons, thus preventing overloading ammonia on the fields, which the plants cannot utilize until conversion to nitrates.
  • Class A water can be elevated to livestock drinking water quality to allow recycling of potassium, sodium, calcium, magnesium, and trace minerals back to the herd at the proper levels.
  • Allows for reuse of recycled water to use to wash down milking parlors and feed alleyways.