Managing Effluent Systems    

Answers to frequently asked questions about managing effluent systems.

What is Best for the Environment, Treatment Ponds or Land Application?    

Utilising dairy effluent on growing plants offers environmental and financial benefits by providing a supply of nutrients to the plant and introducing additional organic matter to the soil, improving soil structure and the associated rooting properties. However, if used in excess it can add to the risks of ground and surface water pollution.

Treated effluent has a reduced nutrient and bacterial load going to the receiving water body, so it currently provides a solution in areas where land application is impractical. However, treatment systems need to be properly sized, sealed, and managed to provide the level of treatment that is not harmful to the receiving environment. Discharge of treated effluent to water requires consent and must meet the conditions of that consent. Advances in land application technology, such as low application rate systems, mean there are very few situations where land treatment is not viable.

back to top

What is the Best Effluent System Out There?    

Industry providers of effluent systems are constantly reviewing and upgrading the products they offer. Each farm is managed differently and there is no right or wrong system, so long as it meets the regulations and provides what you need.

As every farm is different it is advised that when considering a new or upgraded system you should engage a qualified and experienced professional to assess the needs of the farm and create a written plan. This should consider the current effluent output and whether the farming intensity will be increased during the lifespan of the system, for example, increasing cow numbers or building a feed pad.

You should then consult with a number of system designers to find a solution that suits your particular farm, fits within the farm budget and on-farm labour and any geographic or climatic limitations of the farm. A system should be designed to account for changes within the farm business during the lifespan of the system, which could be 10-20 years. The system should minimise the risk of non-compliance and allow for any mitigation if non-compliance does occur.

An accreditation system has recently been established primarily for effluent land application system designers. As companies are approved by the scheme they will be listed on the effluent accreditation website, it is advisable to ask advisors for the relevant qualifications and references.

back to top

How do I Irrigate On Hump and Hollow Land?    

The rules state that no ponding or surface run off of effluent shall occur, so if hump and hollow land is included in the effluent block then application rates should be matched carefully to soil infiltration rates. It may be possible to achieve this through the use of low rate irrigation systems which are frequently removed.

back to top

What is the Best Way to Apply Effluent?    

Effluent application equipment should be matched to soil infiltration rates and the nutrient content of the effluent applied to ensure compliance with Tasman District Council’s rules, and to optimise the value of effluent through efficient timing and application rate.

 Applying high nutrient content effluent as close to the root zone as possible and during the growing period will help minimise nutrient losses during the application process. However, effluent with a low nutrient content can be applied at a higher rate and technology should be matched based on irrigation principles.

Building flexibility into an application system provides the opportunity to maximise on-farm efficiency. Using suitable storage, adjustable machinery, or incorporating different types of technology either permanently or via contracted services, provide farmers with the ability and choice to do this.

back to top

What do I do with Effluent Sludge from my Sandtrap/Feedpad/Pond?    

Effluent sludge from these areas contains a concentrated form of nitrogen and bacteria and therefore poses a risk to waterbodies. The sludge should be managed in an appropriate way to eliminate risk of surface run off or groundwater leaching.

Application of effluent sludge has to comply with the maximum loading rates (for example 200kg N/Ha/year). If the application rate of nitrogen exceeds this then it becomes a non-compliant activity and resource consent must be applied for. Because of the concentration of nutrients in sludges lower application rates are required to stay within these limits.

Further research is being carried out on the benefits of differing types of effluent so best management practices may be reviewed as scientific data becomes available. It is recommended that sludge is tested at the time of application and accurate information is recorded in nutrient budgets so the benefits of these applications on the farm can be measured.

back to top

How Big Does The Effluent Block Need To Be?    

The effluent block should be sized so that it is compliant with Tasman District Council’s application rules. These specifically relate to nitrogen and volume, where nitrogen must not exceed 200kg N/Ha/Yr.

It should also be sized based on the other nutrients present in the effluent. A nutrient budget and routine soil testing can help prevent an excess of nutrients building up in the soil. This can be a particular problem with potassium.

back to top

What Is Meant By Green Water Flood Washing?    

Green water flood washing is the reuse of effluent to wash down areas such as feedpads.

The ability to use green water requires certain conditions be met to minimise the risk of contamination in the milking area. It is important to confirm these regulations with your milk supply company and the New Zealand Food Safety Authority – ‘NZCP¹ Code of Practice for the Design and Operation of Farm Dairies’.

Reusing water on farm can help minimise the amount of water entering the effluent system.

back to top

How Do I Manage Odour and Gaseous Loss From Effluent?    

Odour and gaseous loss in influenced by the dry matter and organic content of effluent. Current research into emissions is limited particularly in relation to the New Zealand climate. Some current management options include:

  • Site effluent facilities away from neighbours and property boundaries.
  • Check wind direction before spreading effluent and time application accordingly.
  • Stir ponds to improve the aerobic breakdown of organic matter within the pond.
  • If solids are separated from the effluent consider the management plan for the solids as well as the liquid.
  • Regularly empty sludge build up from storage ponds.
  • Use additives to help with the breakdown of organic matter in storage ponds.
  • Another option not currently widely used in New Zealand is the use of permeable covers with gas collection and impermeable covers.

back to top