Clean Green Effluent Company
A dairy farmer has developed an automated low rate application effluent system
Clean Green Effluent Company founder Lindsay Lewis has a patented system design for a complete dairy effluent scheme that is fully automated, has no storage ponds, applies effluent water back to land at very low irrigation rates without risk of ponding or leaching, and results into 60% savings in normal fresh water usage.
Lindsay is a third generation dairy farmer from Gorge Road, Southland who designed and marketed an award-winning low-flow effluent distribution system. He built the first installations nine years ago and now has 45 systems nationwide.
The CGE system contains a separator pond with a patented designed weeping wall down the middle. Farm dairy effluent (FDE) is gravity fed through the central pipe to one side of the wall and one half of the pond. After four months the pipe is moved to fill the other side. Solids in the form of sludge stay on the outside of the wall in either of the two halves of the pond. They are scooped out by a 12T digger and applied to land with a muck spreader. That is designed to happen once every 12 months, but varies between 9 and 18 months. Ponds are all the same width but are built longer for bigger herds.
Liquid goes through the wall to a pump chamber. It is stored in 33,000 litre RXP plastic tanks, the number of which increases with herd size. This green water is recycled for external yard wash and returned to the separator pond. Yards are flood washed from the tanks. The use of green water reduces fresh water use in the farm dairy from the average 50-70lt/cow/day to around 20lt. That in turn means much lower volume to be irrigated to land. It can be sprayed at very low rate (as little as 0.25mm/24 hours) on land even in the rain. That avoids the need for storage ponds. Removal of large ponds also reduces rainfall catchment footprint.
The CGE system generates effluent residue which is used for spraying out as paddock fertiliser at a rate sufficient for plant nutrients, but not too much to cause leaching properties. The irrigation is a standard K-line with 20-25 pods in each zone, and four to nine zones depending on farm and herd size. The pumps and the patented controllers ensure that effluent water is applied for just seven minutes at a time, about 0.25mm per application, before cutting off for 10 minutes and diverting to a second pod line for another seven minutes, and so on. That means no more than 7mm is applied per month on any one area. The pods are moved every few weeks.
By applying at 0.25mm application depth, it is safe to apply all year round. This has been backed up by research carried out on Wintering practices by Agresearch.
The low-flow effluent system eliminates the need for settling and storage ponds and greatly reduces the environmental impact of large FDE systems.
The typical cost of a Clean, Green Effluent Company installation is two-thirds of the cost of one large storage pond. Once installed the day to day running costs are enormously reduced, compared to conventional FDE systems.
The quick separation of solids and liquid by the weeping wall (typically two to three hours after flood washdown) means the wall dries out and is more effective with repeat loads. Lindsay says the phosphate and nitrogen tends to stay locked into the solids, therefore further reducing the leaching risk from applications of effluent residue by irrigation.
Each regional council has different effluent storage, irrigation and leaching standards so every CGE system is tailor-made.