Tag Archives: nitrogen in water

The Fight Against Toxic Algae

Signs posted around the Grand Lake, Ohio read: “Danger: Avoid all contact with the water.”  When dangerously high levels of toxins from blue-green algae in Grand Lake, Ohiio were publicized in 2009, many residents and tourists stopped using the 13,000-acre lake in northwest Ohio. Hotel revenue and home values sank for several years as algae bloomed in the state’s largest inland lake.

Greenish water still laps at Grand Lake’s shores, but recent water samples show that the amount of algae-feeding nutrients entering the lake is down significantly. State, federal and private donations covered more than $10 million in projects aimed at improving water quality. More people are boating on the lake again. Grand Lake could now serve as an example for communities with algae problems across the nation, experts say.

Algal blooms are on the rise, from Lake Erie to the Florida Everglades. In August 2019, the Environmental Protection Agency listed algae-related beach closures or health advisories in 23 states, and it said other blooms may not have been reported. In 2010, the EPA found that 20% of 50,000 lakes surveyed had been affected by phosphorous and nitrogen pollution, which feeds algae.e  Cleaning up bodies of water choked with toxic algae has proved difficult. The project to repair Grand Lake, once one of the most polluted by algae in the nation, is one of the clearest successes. It shows cleanup is possible, but also expensive and time-consuming.

“It’s not restored yet, but it’s on the road to recovery,” said Stephen Jacquemin, an associate professor of biology at Wright State University-Lake Campus in Celina.  Beginning in 2012, wetlands areas were built around the lake, which was hand dug in the 1830s. The thick stands of bulrushes and other plants have reduced phosphorous and nitrogen levels in water entering the wetlands before reaching the lake by as much as 90%, Dr. Jacquemin said.  Three wetland areas, which cost a total of about $6 million to build, are constructed as a series of interconnected pools that allow particulates to settle out and plants and microbes to remove nutrients.

Areal View of Artificial Wetlands, Great Lake Ohio

 The state’s Department of Natural Resources has also dredged the lake bottom to remove nutrient-loaded sediment, and tried to clean up one of Grand Lake’s beaches near St. Marys by building a rock jetty and installing aerators and a curtain to filter water. Recent water tests there showed levels below 6 parts per billion of the toxin microcystin, under Ohio’s threshold of 20 parts per billion for avoiding contact with water.

As Green Algae Forces Beaches to Close, Ohio Lake Offers Hope, WSJ, Sept. 18, 2019

The Luxury of Swimmable Waters

Data published in 2013 suggested that it was not safe for people to submerge themselves in 60% of New Zealand’s waterways. “We used to swim in these rivers,” says Sam Mahon, the artist. “Now they’ve turned to crap… [T]he real villains behind New Zealand’s deteriorating water quality are still at large…intensive dairy farms…

The first concern is bovine urine, which is rich in nitrogen. Nitrogen can cause toxic algae to grow when it leaches into water. Nitrogen fertiliser, used to increase fodder yields so that more cows can be raised on less land, exacerbates the problem….

At many of the sites where the government tests the groundwater it contains too much nitrate to be safe to drink—a particular problem in New Zealand, since water in much of the country has long been considered clean enough that it is used as drinking water with only minimal treatment. In Canterbury, one of the most polluted areas, expectant mothers are told to test tap water to avoid “blue baby syndrome”, a potentially fatal ailment thought to be caused by nitrates. The poisonous blooms have killed dogs.

An even greater concern for human health comes from cow dung, which contains nasty bacteria such as E.coli….And then there is the damage to native flora and fauna. The algal blooms suck the oxygen from rivers. Sediment washed from farmland can also choke the life out of streams. Almost three-quarters of native species of freshwater fish are under threat.

…One recent tally suggested that just 2,000 of the thirstiest dairies suck up as much water as 60m people would—equivalent to the population of London, New York, Tokyo, Los Angeles and Rio de Janeiro combined. …

Dairies are trying to clean up their act. Farmers have fenced off thousands of kilometres of rivers to prevent livestock from wading in. Some have planted trees along waterways to curb erosion; others remove animals from muddy fields during winter. Some parts of the country are using more sophisticated techniques: around Lake Taupo, the country’s biggest lake, farmers can buy and sell nitrogen allowances in a cap-and-trade scheme. A technique called “precision irrigation” may curb both water consumption and the leaching of nitrogen.

Earlier this year the National Party launched a plan to make 90% of rivers “swimmable” by 2040. Yet it ignored several recommendations of a forum of scientists and agrarians established to thrash out water policy….Environmentalists argue that the national dairy herd should be cut to prevent further damage…And pollutants moving through groundwater can take decades to emerge in lakes. The worst may still be to come.

Excerpts from New Zealand’s Water, Economist, Nov. 18, 2017