April 17, 2006

 

A small but sturdy looking work boat, negotiating the foul waters of the Miami River, has the ambitious goal of reversing the growth of pollution in this heavily used waterway and thereby enhancing the quality of life along its shores.

In its five years of service so far, the boat, called Scavenger, has played a major part in restoring the Miami River to good health. Its inventor says similar results could be realized along many other rivers and lakes around the world that flow through similar geography and are affected by many diverse sources of pollution.

Except for its bright red color and the occasional bursts from its water cannon, it would be hard to spot the tiny craft, which is about the size of a house trailer. But Scavenger has a heavy responsibility. It picks debris and contaminants from the river's surface and restores the quality of the water beneath. Results of the boat's work in Miami have proved it can:

-- Remove 260 cu ft of surface debris in one week (eight-hour work day);

-- Decontaminate over 24 million gal of water in one week (eight-hour work day); and

-- Introduce enough oxygen into the water to raise dissolved oxygen levels to the maximum that water can contain.

“Sometimes, streams and rivers can recover naturally from pollution,” said Sophie Mastriano, managing director of Water Management Technologies II, the company that made this boat and four others that operate in bodies of water as far away as Nicaragua. “But in active, industrialized areas such as those adjacent to the Miami River, local governments need to intervene to speed up the process or undo specific damage.”

Keeping the river suitably clean is an elusive goal because of new home construction and industrial development along the river as well as pollution from storm water runoff.

“Most of this activity creates large amounts of floating debris and sucks oxygen out of the water—the problems that Scavenger deals with effectively, Mastriano said.

Research conducted by Water Management Technologies II revealed that more than two dozen U.S. rivers and waterways are polluted by similar sources and are sufficiently contained so that a localized treatment system could be effective.

Mastriano said good examples of this are the Willamette River in Portland, Ore., the Des Moines River in Iowa, the Cape Fear River Basin in North Carolina, the Androscoggin River in Maine and New Hampshire and the Detroit River, which links Lake St. Clair with the Upper Great Lakes.

In operation, a single worker drives Scavenger, steering it into the most needy areas and operating the system that collects debris as well as the water cleaning and aeration systems. Occasionally, this person also controls the water cannon that can spray the shoreline to clear debris and also further aerate the river water.

Scavenger operates in a surprisingly low-tech manner in one aspect of its work and is rather high-tech in the other. In collecting surface debris, the narrow boat, with only an 8-ft beam, opens its split bow from the center much like the claw of a giant lobster, dramatically widening its sweep through the water.

In the process, debris on the surface gathers at the base of the claw and is periodically lifted out of the water by a wire basket and deposited into the boat's trash bin. Most of the debris is small in size, including such items as soda bottles, plastic sheets and foam cups. Glass bottles and spray cans are common.

“Natural” trash items such as coconuts, tree limbs and sea grass abound. Dog, cat, chicken and small fish carcasses make up about 2% of the haul.

The water cleaning process relies on the excellent treatment properties of ozone, so extremely unstable that it must be manufactured on board the boat. Production of ozone normally is accomplished by passing air or oxygen through an electrical field such as might be created by two electrodes.

Scavenger's water cleansing system uses such an onboard system to create ozone, which is fed into the 10,000 gal of river water that passes under the boat every minute. In this application, the ozone neutralizes germs and viruses, destroys and removes algae, and removes color, taste and odor from the water it touches.

Then the ozone separates rapidly, providing a generous supply of oxygen to the water it has just recently disinfected.

As a side benefit, operators of the boat have found and notified officials about more than 250 hazards to navigation that were spotted on or just under the surface of the water. Some have been well over 20 ft in length and have included shopping carts, a bookcase and a tent.

“It’s a miracle boat,” said Brett Bibeau, managing director of the Miami River Commission that leases and operates Scavenger. “It’s a floating water recycling machine. It's hard to believe that something this small can do such a big and important job.”

The Miami, long a working river, has become, over time, an exotic and vital urban waterscape without parallel in America. It runs past marinas, public parks, shipping terminals, mangroves, historic homes, waterside restaurants and loading docks through the heart of downtown Miami into Biscayne Bay.

After years of neglect and major declines in river quality because of airport and hospital discharges and oil spills, the River Commission organized local environmental interest groups to develop a plan to refresh the river. In 2000, the commission authorized a demonstration project featuring the Scavenger.

The Scavenger's work was judged a success, and the city of Miami contracted with Water Management Technologies to keep the vessel working on the river full time.