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Operation and Maintenance

All milk house wastewater treatment systems require regular operation and maintenance.

Septic tank and treatment tanks

Excessive solids buildup in the septic tanks reduces the effective hydraulic retention time and allows settled solids to move into the secondary treatment or soil infiltration area. These secondary treatment systems and soil infiltration areas are not designed for this additional solids loading. Excessive organic and solids loading will shorten the useful life of the soil infiltration area.

Septic tanks should be pumped on an annual basis and more frequently if solids accumulate at a faster rate. Septic tanks should be inspected quarterly for scum and sludge buildup to determine when the tanks should be pumped. Tanks should be pumped when solids are 18 inches or more deep on the bottom of the tank or the floating scum layer is 4 to 6 inches thick. This effluent can be land applied.

Solids accumulation in treatment tanks reduces the treatment efficiency of these systems. Monitoring and pumping should be done as recommended by the manufacturer but quarterly monitoring and annual pumping is likely required.

Effluent filter

Effluent filter from outlet of first septic tank ready for cleaning.


Scum layer on top of septic tank.

Effluent filters are commonly installed in the outlet of the primary septic tank to reduce the loading on the secondary treatment system by filtering out suspended solids in the effluent. These filters should be inspected and cleaned monthly initially and less often if these monthly inspections show no signs of buildup. Solids buildup on the effluent filter may indicate a sludge buildup in the septic tank or excessive organic loading to the system. If there is significant buildup on these filters on a regular basis the management and operation of the milk house should be evaluated to determine if waste milk is getting into the system.

Waste milk handling

The Bark Bed, ATU and RMF systems are not designed to treat waste milk (colostrum from fresh cows, waste milk from treated cows or bulk tank failures, or milk spills). The irrigation system can handle some waste milk but excessive amounts may cause odors and will fill the septic tanks with scum.

All waste milk should be diverted from the wastewater treatment system. It is critical that all employees know that waste milk and colostrum cannot enter the treatment system. Plumbing within the milk house will facilitate the diversion of this waste milk from the milk house wastewater system. Check with the milk inspector for requirements regarding milk house plumbing options that will divert waste milk to the manure handling system. Waste milk is often fed to other farm animals.

Human wastes

Milk house wastewater systems are not designed to treat human wastes. Do not allow human sewage to enter the milk house wastewater treatment system.

Rodent control

Rodent control may be needed in valve access pipes, Bark Beds, or drainfields.

Water usage

efficiency and long term viability of the treatment system. As such, flow monitoring is a integral part of the treatment system operation and management. Monitoring this usage aids in troubleshooting any system problems and is used to determine if excessive water is getting to the treatment system (more than what the system was designed for). Monitoring of flow must include notations about any water use measured by the flow meter but not entering the treatment system such as water used for washing vehicles or water used for feeding calves.

System specific maintenance

Beyond these general items, operation and maintenance required for all systems are the system specific items. They are as follows:

• Bark Bed – Inspect for seepage around the perimeter of the bark bed every three months. If necessary add additional bark when bark depth is less than 12 in. Over time, the bark will decompose and additional bark will be needed to maintain adequate cover over the soil infiltration area both to protect and insulate the soil.
• Irrigation – Irrigation zones must be manually controlled for summer and winter operation or if soils become saturated. Monthly checks should be done to insure that irrigation heads are not plugged and no runoff from the irrigation area is occurring. Excessive manure solids and animal hair can plug irrigation heads.
• ATU or RMF – The life of the soil infiltration area following an ATU or RMF is directly related to the treatment efficiency. Monthly visual observation of the effluent will help indicate the unit’s performance. Semi-annual testing of the effluent will document system performance. B_OD₅ concentrations in this effluent should remain below 200 mg/L. Follow other maintenance requirements recommended by the vendor.

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