Managing dairy effluent

Ryan Francis (Email)

Effluent management is often forgotten about until it hits the ‘fan’ (or sensitive receptor, creek, neighbour etc.). Different state legislations and industry codes require that the effluent from dairy premises does not leave the farm boundary and that the system and its operation is designed to manage the system responsibly. Three design and management issues are commonly observed throughout dairy effluent systems.

The most common shortfall of dairy effluent systems is that the ponds are too small and, therefore, the irrigation of effluent is often undertaken when soils are saturated. These design issues can result in ponds overtopping into waterways and irrigated effluent running off paddocks, breaching the codes and legislation. In order to avoid these risks, it is recommended to design effluent storages that are capable to hold all effluent and rainfall within the effluent catchment for any period when soils are saturated (no soil moisture deficit), for a 1 in 10 wet year. While this often results in a considerably larger effluent pond, it also creates peace of mind and ensures the system meets the requirements of the relevant legislation and codes.

Another common issue is nutrient management in the soils which are irrigated. Potassium is often at high levels in the effluent, with 500kg of potassium per megalitre of effluent not uncommon. What is often observed is that this valuable nutrient, being applied through irrigation, is not accounted for and irrigation areas are far undersized for the volume of potassium being applied annually.

The final common issue is solids management. Often fancy solids separation systems are installed to remove solids from the effluent. Mechanical systems such as screens and screwpresses, or travelling solids traps, can result in considerable operational costs due to regular breakdowns, replacement of parts and constant time spent cleaning or emptying. These systems have their place, however if space and gravity are available, a solids pond or sedimentation trench can achieve greater solids separation and require considerably less ‘man hours’ to manage. Solids ponds can be designed to hold several years of solids, if the space is available, and can often be left with minimal management until desludging is required.

So how do we fix these issues? Unfortunately, capital expenditure is often the answer. However, a well-designed dairy effluent system can remove many ongoing operational costs, it can turn the nutrient in the effluent into a valuable resource, it can create a fool proof system that allows easy management for all staff, it can reduce those risks of effluent leaving the property and it can reduce time and operational costs spent on the effluent system.

Pinion Advisory has a team of water and recycled resource specialists who can help to design and monitor effluent systems. Our services aim to improve environmental performance, meet compliance targets and convert waste products into valuable agricultural assets (nutrients, water and carbon).