The management of dairy effluent is a crucial aspect that should not be overlooked. The Code of Practice for Milking Shed Effluent in South Australia is in place to ensure that milking shed effluent and associated wastes do not pollute the environment, unless all reasonable and practical measures have been taken to prevent or minimise any resulting harm to the environment.
The South Australian Environmental Protection Authority (EPA), responsible for enforcing compliance with the Code of Practice, the Environmental Protection (Water Quality) Policy 2015, and the Environmental Protection Act 1993 (Clauses 15 & 20), has recently informed farmers of an increased focus on regulatory compliance for effluent management in the state.
Three design and management issues are commonly observed throughout dairy effluent systems.
Effluent management in dairies and other intensive stock systems requires the system to prevent discharge during a 1 in 10 wet years. The most common shortfall of dairy effluent systems is that the ponds are too small to prevent discharge, often due to gradual farm growth (stock numbers) and, therefore, the irrigation of effluent is often undertaken when soils are saturated (no soil moisture deficit). While the solution to 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. Effluent is a valuable resource that can provide economic benefits to businesses that utilise it in the appropriate manner. However, 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 in terms of the volume of potassium being applied annually. This results in the underutilisation of a valuable resource and increased risk of stock metabolic issues when grazed on the irrigation areas.
The final common issue is solids management. Often, fancy solid separation systems are installed to remove solids from the effluent. Mechanical systems such as screens and screw presses, or trafficable 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 fewer ‘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 experienced dairy effluent designers, 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). These services are offered nationally, and our team is expanding our in-person footprint to include effluent management in South Australia from October 2024.