Can offsetting mitigate the damage caused by nutrient floods from fertilisers and wastewater in our rivers?

Rivers that run through the hearts of Australian cities and towns often carry large amounts of nutrients and sediment.

it’s a problem. While nutrients such as nitrogen and phosphorus are essential to life in small amounts, in large quantities they become destructive to the ecosystems of rivers and oceans.

When rivers are pumped full of nutrients from farms or from wastewater treatment, bacteria and algae numbers soar. We see the effects in dangerous blue-green algae blooms and in oxygen levels dropping to the point where millions of fish can die, as we saw recently in Menindi, New South Wales.

Solving the problem can be costly and difficult for landowners. This is where a new idea can help: nutrient replacement. Here, large sewage plants can meet the stringent requirements of keeping nutrient levels low by stabilizing eroded riverbanks and upstream gullies, creating wetlands, and preventing fertilizer runoff. The end result: cleaner rivers.

While carbon offset schemes have come under considerable scrutiny, nutrient offsets are a simpler market, with fewer participants and clear ways to measure success.

Early trials in south east Queensland by water utilities have proven that they can work, as can ours New report Offers.

Why are our rivers filled with nutrients?

In the early industrial period, rivers all over the world were seen as dumping grounds, from factory chemicals to tannery waste. Since then, many countries have worked hard to clean up their waterways, with major successes including the Thames in the UK.

Chemical dumping is relatively easy to stop. You can see the pipes and decide who is doing it. But nutrient excess is a trickier problem, which is why we still grapple with it.

Our cities and towns are growing. Almost seven million more people live in Australia now than in 2000. As our population grows, we need more food, and we produce more human waste. Our agriculture sector has also boomed and is exporting more and more food items. And in order to make our soil, which is famous for its poverty, fertile, fertilizers are required. When too much fertilizer has been used, heavy rains can wash it into rivers. And the erosion of riverbanks and in the formed gullies is exacerbated.

Some rivers, estuaries and coastal waters get real problems, like parts of Murray-Darling, and some urban streams in our capital cities. We have reached and exceeded the normal limit for handling nutritional loads. This can cause algae blooms, kill fish and the water is too disgusting to drink without expensive treatment.

Why do we need compensation at all?

Chemical dumping can be solved with laws and enforcement. But while we can repair degraded river catchments to reduce nutrient loads, this is rarely done. This is because the costs are too high to be borne by any single sector, such as farmers.

By contrast, regulations on nutrients discharged by wastewater treatment plants set limits on how much can be released into rivers and estuaries. The costs of incremental improvements to wastewater treatment plants to reduce nutrients to the low levels needed are prohibitively expensive, because price-payers will end up paying more for water treatment.

This is why arbitrage can be beneficial, as it presents a win-win situation for both parties. Urban polluters such as wastewater treatment plants can meet their regulatory requirements by restoring eroded and degraded catchment areas upstream to reduce nitrogen and phosphorus fluxes from agricultural lands. Even better, it can be done reasonably inexpensively when done on a large scale. Depending on available sites, this can be done along rivers and streams on rural properties, or on council-owned land in cities and towns.

Making this viable means using the market. Polluters looking for low-cost ways to comply with the regulation of nutrient flows are associated with landowners upstream with degraded land.

This is an emerging solution, but early trials show that it is promising. In densely populated southeast Queensland there are large waterways such as the Brisbane and Logan rivers. Sewage plant operators such as Logan Water, Urban Utilities, and Unity Water have replanted shrubs, grasses, and trees along riverbanks, as well as undertaking engineering work to stabilize eroding banks.

This resulted in significant cost savings. Urban utilities avoided spending A$8 million in upgrading a wastewater treatment plant to reduce nutrients and got the same result by spending A$800,000 in Erosion control and revegetation upriver, which prevented five tons of nitrogen from entering the waterways. Operating costs were also much lower, saving $5 million over ten years.

Erosion control keeps nutrients in the soil to help crops and grasses grow, benefiting farmers, rather than washing them downstream. Healthier riverbanks create better habitat for birds, reptiles, and mammals and make rivers healthier for fish and other species.

What then?

Nutrient replacement is still new in Australia. To gain traction across Australia means working to make sure the systems and science are mature.

To maximize benefits and give participants certainty, we will need to shift from a piecemeal experimental approach to a coordinated trading scheme. Successful examples abroad usually have a third party coordinating the buying and selling, and ensuring that there is a strong structure for preparing and evaluating these projects.

Canada has seen successes here, as has the Southern River Nation trading software which reduced the proportion of phosphorous in the river, while America has examples such as the Chesapeake Bay Nutrient Credit Trading Program. In Australia, it is voluntary Coral reef trading chart Work is currently underway on the river catchment that flows into the waters of the Great Barrier Reef, involving farmers and a group of investors.

To make sure this works, we need detailed scientific knowledge on comparing nutrient contamination from different sources. Nutrients flowing from watersheds are mostly associated with soil particles, while wastewater treatment plants contain more dissolved nutrients. So far we do not know how these sources differ.

We also need to know the most appropriate land management methods to prevent nutrients from being washed into the rivers, to ensure the best outcome for the money spent.

Creative solutions are essential

Despite our efforts to clean up many of our rivers, traditional methods have not been enough to stop nutrient pollution. It’s time to explore new and innovative approaches to making our rivers and reefs healthier.

This article has been republished from Conversation Under Creative Commons Licence. Read the The original article.