Extract pollutants after they enter waterways

DOUG EDMEADES
Last updated 06:52 26/03/2014
Salted away: Desalination plants take seawater in one end and produce pure potable water out the other end.
Fairfax NZ

SALTED AWAY: Desalination plants take seawater in one end and produce pure potable water out the other end.

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OPINION: 'If you can keep your head when all about you are losing theirs and blaming it on you." This is, of course, the opening line to Rudyard Kipling's well-known and much-loved poem If, which wandered into my mind when contemplating recent developments in managing water quality.

There should be no doubt that improving the quality of the water in some of our rivers and lakes is a major challenge confronting our pastoral industry. We must find ways of cleaning up our act without going broke in the process.

But two regional councils, Horizons with its One Plan and Environment Canterbury with its Land and Water Plan, have, by ignoring sound science advice and the wishes of the societies they purport to serve, introduced plans that set unachievable levels for nitrogen leaching. They are unachievable in the sense that to achieve them farmers will go broke.

For example, a client of mine has a large dairy operation in Canterbury. Currently, the estimate N leaching loss is about 120kg of nitrogen per hectare a year. We have looked at many changes to the operation to reduce the N loading, including reducing cow numbers and fertiliser N use, introducing DCD (now banned), building standoff pads and putting in a herd home.

By introducing all these measures the nitrate loading should get down to about 36kg but this will reduce farm profitability about 30-40 per cent. The limit set by the Canterbury Regional Council for this zone is 20kg a year.

The lunacy goes deeper. There are four components to water quality: Sediment, pathogens, P and N, and as I understand it, all catchments are different. The water quality in some catchments will only improve by limiting sediment. For others it is the P loading or N loading that needs to be controlled. If this is so, why is all the focus on N loadings?

And of course all the onus is on the farmer - changing farm management policies and practices is now embedded in our minds as the only solution to the problem.

It is time we started to think outside the square. Why not change the focus away from a farm management problem to an industrial problem? Why not attack it from the other end? Extract or otherwise remove the pollutants after they have got into the water. Think about it!

With today's technology we can build and operate desalination plants - seawater in one end and pure potable water out the other end. Why not adapt this knowledge and approach to the water quality issue?

Imagine: Big irrigation schemes are either in place, being developed or on the books in both islands. Why not tile- drain these soils, collect the drainage water, pass it through a desalination plant, strip the nutrients out and recycle the clean water back through the irrigation system. The accumulated nutrients, of course, would be tomorrow's fertiliser.

This need not be restricted to irrigation schemes. Large flat areas such as the Matamata plains, the Hauraki plains and some areas in Northland, Taranaki, and Manawatu could be similarly developed.

Impossible? Well, Bay of Plenty Regional Council is now adopting this industrial approach. Alum - an otherwise benign chemical - is being added to Lake Rotoehu because it reacts with and precipitates the P out of the water. A physical barrier has been built to divert the "dirty" water from Lake Rotorua (including some urban sewage) down river to the sea rather than into the more sensitive land-bound Lake Rotoiti.

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In the same vein, dairy shed effluent is a potential point source of pollutants. We could industrialise this too.

We send tankers to the farm to collect milk - why not send tankers to the farm to collect the dairy shed effluent. It could be brought back to a central processing plant where its valuable components could be harvested.

The nutrients could be stripped out and recycled into the fertiliser industry, the organic matter could be used to produce biogas and the clean water returned to the farm or added to the municipal water supply.

If we can almost eradicate contagious diseases or put a man on the Moon or build an atomic bomb we sure as hell can develop large-scale industrial solutions to solve our puny water-quality issues, rather than cripple our pastoral industry with endless rules and regulations.

And do not give me the nonsense that this is taking farming further down the industrial path or that modifying soils is not natural. Ever since our ancestors came out of the forests onto the plains they have be modifying soils and industrialising their processes.

One of our human limitations is that we look at the problems ahead through the eyes of our current technology and from this perspective they can look overwhelming.

This myopia traps us into negativity - we think we must go backwards to achieve our goals.

Dr Mike Joy of Massey University, for example, sees the only solution to the water quality issue as, firstly, restrict the growth in dairying and, secondly, de-intensify. This approach is not sustainable - it may achieve some desirable environmental goals but it would come at avoidable economic and social costs.

Let us use our heads not lose them.

*Dr Doug Edmeades is managing director of agKnowledge Ltd and was Agriculture Personality of the Year 2012

- Straight Furrow

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