Choosing an effluent management system
Developing an effective dairy effluent system requires detailed planning. The following things need to be considered:
- soil type
- distance to waterways
- how the system can be integrated into existing infrastructure
- management strategies such as fertiliser applications and irrigation management.
Choosing the most appropriate effluent system will depend on what is:
- more practical
- easier to maintain
- has the potential to return the most benefit.
Key components of an effluent system
Effluent systems often revolve around key components or stages. These are integrated to:
- form the total system
- designed to manage the effluent stream from its generation to its application and reuse.
Components to consider in a dairy situation may include:
- Minimisation of effluent — The more generated at the dairy or feedpad the more that requires storage and application to pastures.
- Solid separation and fibre removal — Removing the coarse material from the liquid stream (such as manure solids, fibre, debris, sand, gravel and stones) reduces the likelihood of problems with other components within the effluent system. These may include pumping, storage, conveyance and application stages.
- Conveyance — How will effluent be conveyed from the point source? Where will it be conveyed too? Can gravity be utilised? What distances are involved? These questions will assist in determining the most appropriate conveyance method.
- Storage or containment — What is the most practical and effective method to contain effluent within the property boundaries over the wetter months of the year?
- Application — Determining the end location for where effluent will be applied is often a good starting point when designing an effluent system. A key principle in the application stage is ensuring effluent can be applied over a significant percentage of the farm paddocks. Application of effluent should be strategically linked to the farm soil fertility targets and fertiliser applications.
- Management — The overall management and ongoing maintenance of an effluent system is often overlooked.
Most effluent systems fail due to inadequate management more so than system design. This component of the effluent system should take into consideration:
- costs of servicing
- ease and frequency of maintenance
- desludging strategies
- staff responsibilities.
On the average size dairy farm simple solutions are often practical and more reliable.
Types of effluent systems
All effluent systems have their advantages and disadvantages— it is simply a matter of choosing the system that best suits the farm variables, location and labour capacity.
Effluent systems are unique and should be tailored to individual farms and not based around what the neighbouring farm is doing.
Direct application to pastures and crops
These systems may bypass effluent ponds and return effluent direct from the point source (dairy) back to pastures or crops using various application methods. The usual approach is pumping from a sump at the dairy back to pastures through irrigation.
- low cost and no pond maintenance
- more effective utilisation of nutrients
- suitable to lighter free draining soils.
- higher likelihood of conveyance problems
- difficult to contain effluent on farm during high rainfall
- fairly labour intensive (moving or repairing sprinklers).
Single storage pond
A single pond system assumes a storage pond capable of containing all the effluent generated at the dairy and or feedpad over the wetter months of the year. A period when rainfall exceeds evaporation and the potential for runoff is likely.
This is generally used to return effluent back to pastures or crops more quickly without nutrients settling out.
- effluent stored and applied to pastures when safe
- more controlled and strategic application
- reduced workload in shifting conveyance pipes and sprinklers.
- dependant on soil type and water table depth
- pond needs desludging every few years and ongoing maintenance
- requires agitation to access the valuable nutrients (with phosphorus and nitrogen settling in the lower layers of the pond).
Dual or multiple ponds are designed for a variety of reasons such as:
- anaerobic digestion
- solid settling
- pathogenic or odour treatment
- winter storage.
- opportunity to recycle reducing the large volumes of water required to service floodwash and hydrant systems
- less conveyance and sprinkler problems
- large water supply rich with nutrients to service nearby pastures or crops.
- requires a significantly large site, which may take away valuable pasture area
- requires regular management and maintenance, in particular the first pond
- tendency to trap and retain the value nutrients within the lower sludge layers, which may be difficult to access.
Slurry tankers and wagons
Although not common, these practices are still viable options for the small dairy farm that may have conveyance problems or limited accessibility to paddocks.
This is usually a preferred option on free draining soils for dairies maintaining a herd dry period. There is a reduced dairy operation over the winter months.
- opportunity to strategically place effluent on specific paddocks
- cleaner collection at the dairy
- emphasises a need to minimise water consumption at the dairy hence water savings.
- may have difficulty accessing lane-ways and paddocks over the wetter months
- labour intensive requiring constant management
- initial purchase costly with regular repairs and maintenance required.
This system traditionally is used as a disposal of waste with very little control.
This system involves gravity conveyance or pumping via an open-end pipe direct from the dairy to a section of the farm considered having little value. This is why it is called 'sacrifice'.
Generally, this is not a recommended method for effluent management and would not meet industry standard.
- low cost due to lack of infrastructure
- little labour required.
- long-term damage to farm and nearby waterways
- no productive use of nutrients
- higher risk to herd health.
Factors to consider
There are some factors to consider when choosing an effluent system.
Legislative and industry requirements
There is a misguided belief that effluent systems revolve around construction of effluent ponds.
Effluent ponds — whether they are anaerobic, aerobic, facaulitive or storage ponds — are simply a component within an effluent system and not necessarily a legislative or industry requirement. In some cases the construction of effluent ponds are not a practical or viable option.
The expectation of the industry — (which includes government departments, water authorities, milk processors, farmer organisations and communities) — is that dairy effluent be contained within the farm boundaries and will prevent pollution of both surface and ground waters.
Installing a practical and cost effective effluent system should get maximum economic benefits from nutrients and improve farm productivity.
Potential daily effluent volume
One of the first considerations in determining the most appropriate effluent system is understanding what volumes of effluent need to be managed. This should include all significant point sources such as:
- loafing areas.
This knowledge will then determine:
- pond sizes
- areas of application
- pumping requirements.
Labour and maintenance
A lot of effluent systems fail not necessarily due to inadequate design, but more so from a lack of management and inadequate maintenance. Some systems such as direct application and shallow ditch systems are labour intensive and require constant management.
Due to the nature of the product (liquid effluent, manure solids, fibre, stones, sand and gravel) it is easy to see why a lack of management or maintenance could lead to system failure.
Ponds are designed to contain effluent for specific periods of the year anywhere from 3 to 6 months. For ponds to be effective they need to be emptied regularly and desludged periodically.
It is pointless designing an effluent system without taking into consideration future development on the farm. It is common for a lot of effluent systems to fail simply because of changes which weren't taken into account when the system was originally designed. (For example, increased herd, installation of a floodwash tank, expansion of the holding yard or incorporation of a feedpad).
Key management should include:
- Developing a whole farm plan.
- Developing an effluent management plan that allows for expansion and modifications to the existing system.
On occasions when selecting the most appropriate effluent system the decision may be predetermined or pigeon-holed into a particular method due to key farm variables.
- Farms with high water tables (1 to 2m) would tend to steer away from inground anaerobic ponds.
- Farms with fine sandy and free draining soil types would have to weigh up the additional cost for pond liners and clay importing options.
- Farms with large storage ponds may not choose tractor-mounting pumps, as it will tie the tractor up for days as it sits on the pond.
Effluent systems are tailored to suit the unique circumstances and characteristics of individual farms. The system design must be cost effective and practical enabling farmers to overcome property limitations by implementing reasonable solutions.
Recycling effluent option
One of the more common practices with the introduction of floodwash and hydrant washdown systems was the option to recycle secondary effluent water to clean holding yards or feedpad facilities.
The option to reuse effluent water is an advantage because it not only guarantees a reliable water source all year, but it reduces the storage pond overall capacity.
Choosing this option also tends to sway the effluent system to a dual or multiple pond system (unless it is a relatively large single pond with an effective solid separation component).
Develop a nutrient management plan
A nutrient management plan takes into account not only effluent application within the farming system but more so detailed nutrient mapping and budgeting programs to develop a more actual representation of the farm's nutrients. The level of nutrients in dairy effluent varies substantially. It is recommended that the individual farm's dairy effluent is tested to give accurate nutrient concentrations to include in the nutrient management plan.
Having this knowledge and greater understanding of the farm's nutrient balance enables more economic and strategic applications of effluent.
Reasons to develop an effluent system
There are a number of reasons to develop and effluent system.
Peak effluent volumes
An effluent system establishes daily, seasonal and future effluent volumes from all significant point sources:
- loafing area
- calf facilities.
Industry expectations for managing effluent
The members include:
- State Environment Protection Policy
- Milk Factory Quality Assurance
- Statutory Planning Requirements
- Government agencies (Agriculture)
Identify all variables specific to the property that may be impacted on by effluent being generated — (waterways, vegetation, neighboring residence).
Identify specific farm characteristics relevant for effluent management — (soil type, water table, depth, layout, herd size, shed type).
How will effluent management be integrated in to current management? (Fertiliser strategies, pasture management, herd health, labour capacity)
Key people or agencies capable of answering technical or legislative questions — (Agriculture pump specialists, design consultants).
Effluent system options
Taking into account all of these reasons — what are the best options for an effluent system? What are the respective costs?
Developing an effluent management plan
An effluent management plan should include:
- system technical designs
- site selection and investigation
- OH&S requirements
- nutrient management
- pond management strategies
- maintenance scheduling
- labour requirements
- contingency plans for breakdowns
- integration into existing farm infrastructure.
- What are the first steps in implementing the system?
Monitoring should occur:
- How often?
- By whom?
For help in choosing the most appropriate effluent system for your farm contact the following Agriculture offices who have specialist staff available: