Effluent systems are made up of many components all of which need to be considered and integrated to achieve an effective system. An effective effluent system should be easy to manage, minimise risk to the environment, and allow for efficient utilisation of the captured effluent, water and nutrients to improve farm production.
When developing an effective dairy effluent system, detailed planning is required to ensure the system suits the farm's requirements and overall production system, taking into account:
- farm characteristics such as soil type, topography, climate and distance to water ways;
- integration with new or existing infrastructure;
- management including herd size, production potential, time on concreted surfaces; and
- the long-term vision for the property.
The ultimate aim of any effluent system is to return nutrients to under producing land or improve yields of crops and pastures as this is where an economic benefit can be realised. It is important while doing this to consider and minimise potential herd health issues such as grass tetany, milk fever, Bovine Johne's disease or mastitis.
The key principles in effluent system design are to capture, collect, separate, convey, store, recycle and reuse effluent. This means:
Capture the washdown water and rainfall from animal holding areas including dairy and holding yards, feedpads, loafing areas, laneways and underpasses.
Collect rainwater, effluent and manure in a sump, trap, ditch or pond.
Separate (in some instances) a portion of solids to increase effluent quality for reuse and recycling either passively (e.g. sedimentation pond or weeping wall) or mechanically using an incline screen or screw press as examples.
Convey effluent between components through a pressurised pipe with a pump, gravity pipe or open drain to a storage.
Store effluent during the wetter months of the year to maximise nutrient and effluent utilisation. Ponds are often used as they are the most cost-effective option though in some situations, tanks or direct application may be more suitable options.
Recycle effluent, generally from ponds, for holding yard or feedpad alley washdown.
Reuse nutrients and effluent on pasture or crops. Effluent can be applied through a large range of irrigation systems, from travelling irrigators to pivot and lateral move irrigators to border check irrigation systems. Slurry tanker and umbilical systems are also an option for spreading effluent on pasture and crops. It is not acceptable to use an open-ended pipe to convey effluent to a sacrifice area, as this may lead to paddock runoff or a nutrient overload to the area.
The components of the effluent system need to 'fit' together otherwise the system can and will fail. One common example is converting dairy yard wash from hose to flood wash.
The flood wash system may use double the volume of water that hose washing uses. The rate the water is released is also different. When hose washing the dairy yard, it may take 20-40 minutes to wash the yard while the flood wash releases the volume of water in a matter of minutes.
The dairy sump and pump may be able to cope with the slower flow of water from the hose but may be too small to contain the large influx of water from the flood wash system, potentially resulting in uncontained effluent. In this situation, the sump size should also be increased to allow for the increased water volume and the pond capacity reviewed to ensure additional water doesn't compromise winter storage.
This is just one example of a component change which may result in a system failure. Any change which results in increased load on the system, either from manure loading or increased water usage or catchment area, can lead to increased maintenance and inefficacies in the system.
It is also important when making farm changes to review, monitor and upgrade the effluent system. Some of the changes include increase in herd numbers, increase in water usage, having long periods of animals on concrete holding yards, or addition of a feedpad, therefore creating another effluent stream.
Effluent system design can be complex and careful planning is required to ensure the system functions effectively to contain and reuse nutrients in an economic and productive way. An effluent system designer will be able to assist putting together a system with the knowledge of how the different components will interact.
A list of service providers who have achieved a level of competence based on successfully completing all assessments and course requirements for the nationally recognised Design Livestock Effluent Systems course (Unit AHCLSK 506A) delivered by the Agriculture Victoria in partnership with Dairy Australia can be found at http://agriculture.vic.gov.au/agriculture/dairy/managing-effluent/effluent-system-designers.
These service providers will be able to provide an Effluent Management Plan, which are a document containing the 13 key elements important to effluent design and management. They provide information on:
1. Statement of intention.
2. Property background and scale of enterprise.
3. Statement of the farm's current effluent system and management.
4. Contributions to the effluent stream (water audit).
5. Environmental variables specific to the farm.
6. Effluent system options and design specifications.
7. Effluent system siting and integration.
8. System management notes.
9. Effluent conveyance and application notes.
10. Nutrients (budgets and mapping).
11. Manure stockpile management (whole property).
12. Occupational health and safety requirements.
13. Contingency measures.
Consistency of information through developing an Effluent Management Plan enables effective and practical implementation of the effluent system and investigates the planning requirements of the various government agencies. The plans should be developed in consultation with the farmer to ensure a practical effective effluent system is implemented that is easily maintained, suits the physical characteristics of the property, and maximises the reuse potential of the effluent while minimising the risk to the environment.
