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Competency Area 8: Concentrated source pollution AEM

PO 77. Understand the advantages, disadvantages, and situational appropriateness of various options for handling milking center waste and/or other process waste waters.

  1. Septic systems/leach fields
  2. Vegetative filter areas
  3. Aerobic lagoon
  4. Organic filter beds
  5. Constructed wetlands
  6. Stone-filled trench
  7. Lime flocculation
  8. Spray irrigation
  9. Aerobic septic system
  10. Inclusion in liquid manure handling system

Septic systems/leach fields – Septic systems and leach fields are typically low in cost but are not generally suitable for treating large volumes of milking center or other process waste waters. Leach fields are easily clogged with overflow of suspended milk solids.

Vegetative filter areas – Vegetative filter areas are more costly but are reasonably effective in treating process wastewaters, providing certain design and maintenance criteria are met. Some examples of these criteria include settling and screening out solids and large organic debris, using effluent distribution methods that provide sheet flow across the entire filter area, sizing the filter area appropriately based on hydraulic loading and nutrient loading and removal criteria, and locating the filter area on suitable soils that can absorb, adsorb, and process the nutrient loads.  For milking center waste water, it's important to settle out the suspended solids first, and provide good effluent distribution on soils that adsorb phosphorus. For silage leachate collection and treatment systems, the highly concentrated effluent should be diverted or diluted to avoid vegetation kill zones in the filter area.

Aerobic lagoon – The advantages of an aerobic lagoon are to provide storage and disposal flexibility, they may use less land around the facility for treatment, there may be opportunities for liquid recycling, wastewater treatment becomes a part of the nutrient management plan when the effluent is removed, and they often entail lower labor needs and operating costs. Disadvantages of an aerobic lagoon are offensive odors may occur, aeration may be necessary, overtopping may occur (or effluent and sludge removal may need to be more frequent, especially if undersized), and the potentially high volumes of storm water runoff from barnyards and feed storage areas often necessitate an increase in size and cost.

Organic filter beds – Organic filter beds are suitable for small wastewater volumes and are quite effective at removing ammonia-N. However, they may actually release P as the organic filter media decomposes. The main disadvantages of an organic filter bed is the cost is generally prohibitive to treat large runoff volumes and the organic media beds need to periodically be replaced as they decompose. In New York, organic media beds are no longer being recommended because of their unpredictable performance and high maintenance requirements.

Constructed wetlands – The advantages of constructed wetlands are they are capable of providing a high level of treatment, inexpensive to operate and largely self-maintaining, can handle variable loadings, and they may reduce the amount of land needed for land application. The disadvantages are the direct inflow of concentrated process wastewaters may kill vegetation (hydrophytic plants are quite sensitive to high ammonia levels), large influxes of runoff induce large changes in water levels, thus reducing treatment reliability, and they may require water inputs during non storm events. Furthermore, constructed wetlands require a single dedicated land use, can potentially harbor mosquitoes and generate offensive odors, and are often more expensive to construct than other treatment options. Because of these disadvantages, other pre-treatment facilities (e.g., low flow collection, surcharge storage) are usually still needed.