BioFiltro Dairy Effluent Treatment

October 2012

An environmentally friendly dairy effluent treatment option for dairying

Papawai Ltd is a 560 cow dairy farm near Winton. The property is just under 220 ha effective. They’re producing around 250,000 kg/ms.

The farm is owned by Dallas Lucas and Peter Donnelly – the sharemilker is Matt O’Brien.

For the last four years the farm has been using an innovative, environmentally friendly system for treating shed effluent called BioFiltro®. The basic idea is that vast hordes of tiger worms deal with the cow effluent, turning it into highly valuable humus and producing a translucent liquid discharge. It is the first farm-based operation of its kind in New Zealand.

When Dallas Lucas took on the farm he inherited an effluent system that was unsustainable in the long term. It had little storage and certainly wouldn’t have met the new codes of practice being introduced. He says he and his business partner explored many options while researching a replacement effluent system but were unconvinced about holding ponds.

They did not want to install the 3.6 million-litre pond they would have needed to meet the requirement of having 90 days’ storage. He says Environment Southland would have wanted a 2m-deep pond with a surface area of 1500m2 just to look after the current herd size. They wanted a simple system with room for expansion.

What they’ve come up with is a 150m2 BioFiltro® worm farm with a weeping wall.

The reasons were environmental, room for expansion and a reduction in labour. Dallas jokes that the worms work for free, there’s no employment contracts and they work day and night.

Dallas says it probably would have been preferable to be the 3rd or 4th farm installing a system like this, rather than the first given there’s teething problems with any new system. However he likes what he sees so far and is pretty happy with the decision to go with BioFiltro®

The BioFiltro® Treatment System was developed in Chile, where it was dealing with human effluent from a town of 12,500 people, as well as waste from a meat processor and a cheese factory.

Over the last 18 years the Chilean engineers have installed over 80 BioFiltro® plants – these range from communities with a population of 15,000, to industrial plants that process wine, fish, meat and dairy wastewater of up to 8 million litres/day.

The environment in which these plants operate is diverse and challenging; from the extreme heat of the Atacama Desert, to the frozen continent of Antarctica. Plants have also been constructed in France, Spain, Mexico, Paraguay, Brasil, and Uruguay.

The technology was introduced to NZ in 2006 and the system is being used to treat wastewater and effluent ponds in both the South and North Islands (including Balclutha and Edendale).

Its use on farm is relatively new but the system uses similar principles.

Shed and yard water flow into a containment area with a weeping wall that holds back up to 80% of solids. The wall and containment area is divided into two sides, each designed to hold solids from one season’s milking, then in the second year, allows solids to dry, for later spreading onto land.

Under the BioFiltro® system, water from the weeping wall is pumped to buffer storage tanks and then pumped out over the BioFiltro® beds.

The bed is the heart and soul of the system The shed effluent is pumped from the storage buffer tanks onto what looks like a big bed of sawdust. The beds can cope with around 40,000 litres per day.

In the bed is a living system – micro flora – along with hundreds and thousands of tiger worms feasting on all the bacteria inside the media. That bacteria requires oxygen to survive and worms do that by burrowing and oxygenating the bed.

As bacteria breakdown the effluent, the worms get to work, eating their own weight in organic matter each day. Effluent is transformed into nutrient rich humus (a soil-like residue) and a translucent liquid discharge. They reckon the humus is so good you could “put a pencil in it and grow a tree”.

It’s a treatment system not a storage system. The plant bed and weeping wall occupy a much smaller area than holding ponds. The manufacturers say there are significantly less pollutants: BOD5 (a measure of the organic content of waste water, but literally the biochemical oxygen demand over five days), suspended solids and fecal coliforms.

The Clutha District Council has retrofitted BioFiltro® to some of their waste water schemes. Largely this has been done to improve water quality discharge from their oxidation ponds. In the council systems, the BioFiltro® beds have been added to the end of the system and incorporate UV filtering and a lime filter. That is then discharged to water. Their engineer says in the case BioFiltro® was a lot cheaper than any alternatives. He says that in a waste water system the BOD of raw sewage is around 250 or 300. On waste water systems like the one operating at Tapanui – with BioFiltro® attached – the BOD is down to 8 or 9.

The treated water from the BioFiltro® system running on farm can’t be discharged to water. The liquid can be applied at times to maximize plant growth and minimize run off. If there is run off, the effect on the environment is minimal.

The cost of the BioFiltro® farm system is said to compare to setting up a newly consented sealed 90 day pond system

The BioFiltro® folk say that normal cleaning chemicals or antibiotic use will not cause system failure

The treated effluent receives UV treatment to meet consent conditions for discharge into waterways (but this is NOT being done here) or alternative disposal options e.g. spray irrigation .They also say that treated effluent can be used to clean yards, reducing water use by 40%.

In Southland the system attracts longer consent periods for discharge of effluent. The consent is currently sitting at 15 years. They also claim that maintenance is very low and the whole system can be monitored remotely.

Dallas Lucas hopes they will eventually be allowed to use the treated wastewater to wash down the yard, potentially reducing their water use by more than 30 per cent.

One of the main benefits was the size of the bed, which needed significantly less space compared with a traditional lagoon-based system.