Q: What are the advantages of building effluent storage?Show/Hide the answer
A: There are a number of advantages gained from building effluent storage;
- Ability to store effluent during the winter or early spring and prevent applying when plant growth is slow and soils are saturated.
- Ability to reduce work load demand during busy periods such as calving in early spring.
- Reduce leaching or ponding of effluent by having the ability to store during periods of prolonged wet weather.
- By more strategic use you can apply effluent when plants are actively growing resulting in increased growth and reduced use of Nitrogen based fertilisers.
- By storing effluent you may have the ability to apply a lower rate over a larger area resulting in better utilisation of Potassium (K) and Nitrogen (N).
Q: Do I need a sand trap in-line with my effluent system?Show/Hide the answer
A: It is recommended that you maintain a sand trap within your system. Some farms and shed builders have removed them which allows heavy sediment to enter the storage ponds. This can make for expensive cleaning or de-sludging at a later date. If the sand and small stones are kept out of the ponds the slurry can be agitated to a point where it can be easily pumped.
Q: How deep can I build my pond?Show/Hide the answer
A:The anaerobic pond in a two pond system should be 3.5 m deep. The aerobic on the other hand should not exceed 1.5 m in depth. Single ponds with stirrers can vary from 1.5 m to 3.5 m deep.
Q: What are the advantages of a two pond system?Show/Hide the answer
A:The aim of a two pond system is to remove the heavy sediment and organic matter from the raw effluent so the by-product (grey water) can be injected via the irrigation system, (pivot, k-line etc). The major benefit of a two pond system is that they can generally operate under gravity meaning less potential for problems and costs associated with pumps and stirrers.
Q: What is the best effluent system for me?Show/Hide the answer
A: There are many different systems available including screw press separators, two pond systems and weeping walls. In most cases raw effluent needs to go through a primary treatment which is removing the solids. The grey water by-product of this usually needs to be stored which prevents having to apply during undesirable times.
Liner Irrigation Storage
Q: How deep does my storage pond have to be to justify installing a Geo-membrane?Show/Hide the answer
A: With most liners costing between $10 and $12 per square metre, it is important to get maximum utilisation of the liner by creating a deep storage facility. For the proposal of newly constructed lined storage a minimum depth of 8 m should be used as a bench mark.
Q: Do I need consent for a larger lining pond?Show/Hide the answer
A: Any storage structure which dams water to a height of greater than 3 meters triggers the Building Act, thus a building consent will be required for larger deeper ponds and a consent to store water may also be required depending on what the regional council’s legislation is.
Q: How steep can I build my inner walls?Show/Hide the answer
A: With high hydraulic loads being created with this depth of water, the floor and inner banks need to be compacted with a heavy construction roller. These rollers generally are limited to effectively operating on a gradient no steeper than 1:3, thus it is recommended that the inner gradient does not exceed this.
Q: What if I have concerns over a high water table?Show/Hide the answer
A: The base of a storage pond needs to be constructed above the water table at its highest point. Building these structures in areas that can be affected by high or rising water tables can create logistical problems during construction, lining installation and general operation. If the water table could become an issue or the exact water table is unknown, it is advised that test holes be dug to identify an accurate assessment. This should be investigated during periods where it is thought to be at its highest point, generally winter or spring. It is also advised that this is done as early as possibly before site selection or design commences.
Q: Is the desired location for my storage pond on a flood plain?Show/Hide the answer
A: The Regional Councils have very strong views on trying to build such structures in or over flood plains. Flood plain areas are likely to create some scrutiny during the consent process, prolong consenting time, and in most cases be rejected. Also, it is not always the case, but as a general rule of thumb flood plain areas generally have a high water table as they are close to rivers or water bodies.