In This Section |
Handling Milking Centre Washwater in an Environmentally-Responsible Manner
Table of Contents
What is Milking Centre Washwater Disposal?The introduction of the pipeline milking system in the late 1960s was a welcome improvement for dairy farmers everywhere. At the same time, a new problem was created - what to do with the large quantity of water required to clean and sanitize the milking equipment and pipeline. Equipment used during the milking of livestock must be rinsed, washed, acid rinsed and sanitized. Through this process, washwater is exposed to high concentrations of chlorinated alkaline solutions, acidified waters, and heavy detergents that are not environmentally safe if improperly handled. Milking centre washwater must be handled in a manner that will not harm the environment. Included in this Factsheet are various proven techniques and new treatment methods for handling milking centre washwater. Washwater contains phosphates from detergents and concentrated phosphoric
acid that is used to clean and sanitize milk lines and equipment by
trapping and dissolving oils and grease. Phosphorus is a main contaminant
in surface water that leads to eutrophication. Eutrophication causes
an increase in aquatic plant growth, a decrease in oxygen levels, minimizes
transmittal of light and harms aquatic life. Proper storage and handling of phosphorus in the milking centre washwater
will protect surface waters from eutrophication. Phosphate-free soaps
are not an acceptable alternative to proper storage and treatment since
the phosphates are usually replaced with nitrates. Nitrates from soap
and manure can lead to contamination of surface and groundwater. Milk
in the washwater is also a contaminant. Decomposing milk uses oxygen
while associated bacteria are known to transmit disease.
| Top of Page | Quantity of Washwater ProducedMilking centre washwater may result from dairy, goat and sheep operations. To select and design the best system for your farm, determine your approximate daily washwater production. A survey of 300 Ontario dairy farms found the average washwater produced was approximately 14 L/cow/day (3.1 imp. gal/cow/day). This amount varied from a low of 6 L/cow/day (1.3 imp. gal/cow/day) to more than 28 L/cow/day (6.2 imp. gal/cow/day). For dairy operations with a pipeline milking system, the average daily washwater production was 14 L/cow/day (3.1 imp. gal/cow/day) and for operations with a milking parlour, it was only slightly higher at 17 L/cow/day (3.7 imp. gal/cow/day). The amount of milking centre washwater produced by dairy milking cows is illustrated in Table 1. For more milking cows than shown in Table 1, use the washwater production numbers outlined in Table 2.
* Based on: dry parlour, bulk tank cleaned out
once a week, and no prep on does.
These numbers should only be used to obtain an estimated water use. It is important to accurately measure your specific water use to properly select and size the system that is best for you. Measure your actual water use by installing a water flow meter or estimate it using a calibrated pail or the sink if you know its capacity and a stopwatch to time the water flow. If using an excessive amount of water, reduce this amount to make the disposal system work properly and reduce the amount of storage and handling required. To reduce water usage, use proper calibration, adjustment of pipeline and bulk tank wash cycles. Also, use recaptured washwater for cleaning floors and direct clean water such as the overflow from heat reclaimers away from the floor drains. Ensure that any steps taken to reduce washwater do not adversely affect the cleaning of the milking system. | Top of Page | Storage and Treatment SystemsStorage and treatment systems must be properly designed, installed and operated to be economical, compatible with current washwater and manure handling systems on the farm, and effective in preventing pollution of surface or groundwater. Three methods have been proven to be the most acceptable for handling milking centre washwater in Ontario:
Other systems have been developed more recently that are also capable of handling milking centre washwater. They include:
Adding to Liquid Manure or Runoff StorageA proven means of handling milking centre washwater is to add it to liquid manure or manure runoff storage (Figure 2). The milking centre washwater can then be applied to the land along with the liquid manure or runoff material. Consider this alternative if:
If you are planning for an additional manure and runoff storage, it must be designed and constructed following the Nutrient Management Act, (NMA) Ontario Regulation 267/03, as amended, if your farm is phased in under the Regulation. It is a good practice to follow the requirements of the NMA, regardless of whether your farm is phased in or not. The municipality that administers the Ontario Building Code will also have requirements that must be met before obtaining a building permit. Liquid manure systems require 240 days (with exceptions) of storage. Concrete, earthen and steel storage facilities are commonly used methods of containing liquid manure or runoff. Any concrete or steel storage that is adequate for liquid manure will also be adequate for storing milking centre washwater. Earthen storages may require a greater clay content to store milking centre washwater as opposed to liquid manure because the washwater may not have the amount of solids to promote sealing of the clay. Further information on the siting, sizing and design of manure and runoff storages is available in NMA, Reg. 267/03, as amended. Adding milking centre washwater adds very little fertility value to
the manure but diluting manure solids makes agitation and pumping easier.
When land applying the manure and washwater be sure to follow procedures
and practices that prevent ground and surface water pollution. For requirements
on land application of manure and washwater see NMA, Reg. 267/03, as
amended.
| Top of Page | Separate StorageMilking centre washwater may also be collected and stored in a separate storage (Figure 3). This storage should have capacity for a minimum of 240 days of washwater production. Consider this alternative if:
Milking centre washwater can produce offensive odours during warm summer
weather. It is wise to locate open storages at considerable distances
from neighbours' dwellings and from the farm family's living area. Check
with your municipality regarding siting of the manure storage to meet
the Minimum Distance Separation Formula II and any other municipal requirements.
| Top of Page | Sediment Tank and Treatment Trench SystemA sediment tank and treatment trench system is the third method of handling milking centre washwater. This system requires a building permit and is regulated under the Ontario Building Code (OBC), Part 8 under the Building Code Act. The design, construction, operation and maintenance of these systems must meet the minimum requirements set out by this regulation. The following conditions for installing a sediment tank and treatment trench system must be met:
Setbacks from landscape features have different requirements for both the distribution pipes in the treatment trenches and the sediment tanks. The setback distances contained in the Ontario Building Code must be followed. The sediment tank and treatment trench system should only be considered if the following can be adhered to:
A sediment tank and treatment trench system consists of a sediment tank and several treatment trenches. The purpose of the sediment tank is to collect solids that are washed down drains and to prevent floating material from blocking the treatment trench lines. The treatment trenches distribute the liquid from the sediment tank over a large area to allow it to percolate into the soil. Bacteria attached to the stone in the treatment trench help to remove contaminants in the milking centre washwater; other contaminants like phosphates are trapped and degraded by the soil. The success of the sediment tank and treatment trench system depends on the principal of treated water draining away from the distribution pipes. Therefore, this system works best in well-drained soil types. Where finer soils exist, it may be better to use another option. It is important to follow the design details outlined in OMAFRA Publication 28, Milking Centre Washwater Disposal Manual, Chapter 9 for this system to work satisfactorily. The treatment trench area should be seeded to grass and also fenced
to prevent heavy traffic and livestock from damaging the system. Remove
all water-loving trees, such as willow, soft maple, elm and poplar for
a distance of 30 m (100 ft.) from the treatment trench area. Remove
other trees and shrubs if they are within 15 m (50 ft.) of the treatment
trench. The sediment tank must be large enough to retain the wastes until the
solid particles can separate out. A minimum retention time of 4 days
is recommended but 6 days is preferable. The retention time is equal
to the capacity of the sediment tank divided by the daily washwater
use. The tank must also provide space for 6 months or more of accumulated
solids. An approved 2-compartment septic tank with a minimum capacity
of 3600 L (800 imp. gal.) is satisfactory for operations producing up
to 680 L (150 imp. gal.) of washwater per day. The disposal field includes distribution piping and treatment trenches.
Use connecting pipe from the sediment tank to the distribution pipes
in the treatment trenches. If the connecting pipe must go under a roadway,
replace it with galvanized steel pipe to prevent damage due to heavy
vehicles or frost. Excavate the treatment trenches with a backhoe in parallel lines at least 2.4 m (8 ft.) on centre. The trenches should be 18-30 m max. (60-100 ft. max) in length. Install a minimum of 2 treatment trench lines per system. Excavate trenches 0.5-1 m (20-40 in.) wide and at least 0.75-0.9 m (30-36 in.) deep. The minimum depth from the bottom of the treatment trench to the top of bedrock or high groundwater table must be 0.9 m (3 ft.). Partly fill the trenches to a depth of 0.3 m (12 in.) with 19 mm (¾ in.) septic stone or 19-53 mm (¾-2 in.) clean, screened gravel to make an aerated treatment bed. Lay the distribution pipe at a uniform slope of 0.3%-0.5% away from the tank, with the holes facing down in the 4-6-8 o'clock positions. Add more septic stone or gravel to provide 50 mm (2 in.) of cover on the pipe and a layer of filter cloth to keep soil out of the stone bed. Backfill to the top of the trench with the excavated topsoil (Figure 4). DO NOT use plastic drainage tile, as the perforations are not large enough and will quickly become plugged. Tables 4 and 5 provide minimum treatment trench dimensions for milking dairy cows (Table 4) and goats/sheep (Table 5). | Top of Page | Figure 4. The sediment tank and treatment trench system is an alternative for handling milking centre washwater.
* Part 8, OBC requires a minimum total length of distribution piping of 40m (131 ft.) regardless of daily flow to the system.
| Top of Page | Make your sediment tank and treatment bed large enough to accommodate any foreseeable future herd expansion. Have a licensed engineer/contractor knowledgeable in milking centre washwater disposal systems install the treatment system. Waste milk, milk from treated cows or waste colostrum must never be disposed of through the sediment tank and treatment trench system. This system is not designed to "treat" milk. In the event of a milk spill, pump out the sediment tank and properly dispose of immediately. The first 10-15 L (2-3 imp. gal.) of the first rinse cycle composed of a high percentage of milk must be collected before it enters the sediment tank and treatment trench system, as even a small amount of milk going down the drain every day will eventually plug the system. One method of disposing of this first rinse is to feed it to calves. There is not enough milk in this rinse water to contribute significantly to the nutritional requirements of young calves, but it can be fed to older calves already weaned, or used as the liquid to reconstitute milk replacers. For calves one month of age, the first rinse can be added to milk to provide additional liquids. If this system is used to treat water from a milking parlour, do not
wash manure from the parlour into the sediment tank, as this could completely
fill the system with solids in a week or less. Shovel all manure solids
into manure alleys or gutters of adjoining barns before washing walls
and floors into the washwater system. To wash solids from the milking
parlour through the floor drain system, connect the system to a liquid
manure storage tank and not to the sediment tank and treatment trench
system. With proper design, management and soil conditions, these systems can work quite well. Historically, many systems have failed, however, the cause of failure was often related to the disposal of excess milk and water through the system. It is illegal to dispose of human wastes through any of these washwater systems. If installing a toilet, it must be connected to a separate septic tank system approved by the local regulatory agency. | Top of Page |
|
||||||||||||||||||||||
This site is maintained
by the Government of Ontario
Queen's
Printer for Ontario
Last Modified:
