September 2006, Vol. 18, No.9

Problem Solvers

Problem Solvers - Water Decontamination Vessel Restores Lake

Problem: Recycling company in violation of local water pollution standards.
Solution: Increasing DO level in lake.

In the mid-1990s, Waste Magic Recyclers Central Inc. (Palm Beach, Fla.) received notice from the Broward County (Fla.) Department of Natural Resource Protection (DNRP) that it was in violation of local water pollution standards, based on high levels of contaminants found in a lake on its property. Located in the heart of an industrial park, Twin Lake was surrounded by several local businesses, including a cement plant, a trucking company, and a travel-trailer park.

Years of watershed runoff and a steady stream of chemical pollutants made Twin Lake smell terrible and look even worse. DNRP warned Waste Magic Recyclers that it would face significant monetary fines if it did not take immediate action to bring the lake into environmental compliance.

Water quality monitoring conducted by DNRP in November and December 1995 showed that Twin Lake suffered from greatly reduced levels of oxygen in the water. Over the years, the lake had deteriorated as the result of two basic environmental conditions: breakdown of the land comprising the lake’s watershed and threats to water quality from runoff carrying chemical insecticides, fertilizers, septic tank leachate, and more.

The agency found that dissolved oxygen (DO) depletion and hydrogen sulfide-type odors were the result of excessive organic loading in the lake water. High levels of biochemical oxygen demand had resulted in depressing DO to severely low levels in the lake. DNRP gave the company two options: Find a way to bring the DO levels back to an acceptable level or face environmental penalties.

In 1997, the company turned to Water Management Technologies (Baton Rouge, La.) to enlist the aid of its Scavenger Decontamination Vessel. The goal was to use the company’s onboard oxygenation system to revitalize the lake and bring the DO concentration in Twin Lake into compliance with the DNRP standard of 4.0 mg/L.

The Scavenger applies an advanced water decontamination system to treat and revitalize waters, ports, and beach areas by aerating the water directly with a combination of ozone and oxygenation. The boat improves water quality by reducing and eliminating bacteria and viruses, controlling algae growth, improving water clarity, and eliminating odors.

The vessel’s Oxy-PlusTM technology pumps oxygen and ozone directly into the water. When oxygen is pumped into infected water, the enrichment contributes directly to reducing toxins suspended in the water.

With the addition of ozone to the aeration process, a powerful and environmentally safe disinfection occurs in the waterbody being treated by the Scavenger 2000. Ozone has been used in municipal sewer treatment processes worldwide because of its ability to disinfect water without leaving the harmful byproducts that chlorine disinfection leaves behind. Ozone alters the surface charge, allowing suspended particles to coagulate and be easily removed. It filters most pesticides and other polluting chemicals, and it improves the water’s DO content, which has a rejuvenating effect — a key factor in revitalizing Twin Lake.

To achieve the desired results, Water Management Technologies divided the lake into four operational sections, with treatment at various depths, covering depths up to 0.9 m (3 ft), 1.8 m (6 ft), and 3.7 m (12 ft). Following initial tests for each section, and based on those results, a treatment time was established for each part of the lake. Scavenger operated for 173 hours during approximately 4 weeks, injecting oxygen into the water at a rate of 28 m3/min (1000 ft3/min) of air, along with ozone.

At the end of the contract period, test results showed that Scavenger had raised DO levels in Twin Lake above the 4.0 mg/L required by DNRP. The newly reoxygenated and revitalized water in the lake prompted rejuvenation among natural wildlife, resulting in the return of a healthy bird, fish, and turtle population to the lake.

Based on the results of the Twin Lake cleanup, DNRP notified Waste Magic Recyclers that the company had achieved the required compliance level, and the agency withdrew its threat of environmental fines.
For more information see, or contact Sophie Mastriano at (954) 668-6937.  

Small Mixer, Big Results

Scientist and engineers turn to nature for inspiration for water mixer

Problem: Stagnant water reservoirs.
Solution: Small mixer uses blueprint from nature to reduce thermal stratification and minimize microbial contamination and nitrification.

“Natural capitalism,” the brainchild of environmentalists Paul Hawkin and business visionaries Amory and Hunter Lovins, is a set of guidelines to transform societal systems toward sustainability. Biomimicry — one of the four principles of the natural capitalism framework — is an idea Carollo Engineers (Phoenix) has been investigating for use in the water and wastewater field for several years (see WE&T, December 2002).

Carollo’s investigations led the firm to PAX Scientific Inc. (San Rafael, Calif.), a fluid-sciences research and development company. PAX Chief Executive Officer Jayden Harman identified a basic principle that nature applies universally to reduce friction and drag in flow structures, plants, and animals. In nature, everything spins or moves in spirals, rather than in straight lines. Harman adapted this core principle into the PAX Streamlining Principle, which is employed to optimize fluid movement, manage turbulence, and reduce friction, drag, energy use, wear, noise, and heat. PAX created an impeller based on nature’s flow geometry that can be used in pumps, fans, propellers, and mixers.

Working together, Carollo and PAX identified several applications for this technology in the water treatment field, including mixing, aeration, and pumping, and selected one — mixing — that was low risk, but relevant, to validate the technology. Carollo designed and conducted a series of field tests to validate the technology for reservoir mixing to prove that it worked, develop some basic parameters for its operation and application, and confirm its applicability to the problem of mixing water.

The Problem
Many municipal water utilities have large potable water reservoirs in their distribution systems. Stratification due to solar heating causes a stagnant layer of water to form at the top of the reservoir that can lead to increased water age, low disinfectant residuals, and growth of bacteria, which can expose consumers to health risks. Compounding this issue is the fact that cooler water from the distribution system usually enters and leaves the bottom of the tank through a single inlet–outlet pipe. To combat this issue, many systems are modifying their reservoirs to mix the water within them. Some of these systems include separating the inlets and outlets, installing check valves, and adding mechanical mixers. Costs, benefits, implementation issues, and effectiveness vary from system to system.

Demonstration Test Results
A small PAX mixing device was tested in several municipal potable water storage tanks ranging in size from 3.8 million to 15.1 million L (1 to 4 million gal). The PAX-designed mixer provided reliable mixing with low-energy use and material requirements. In the 15.1 million-L (4 million-gal) reservoir, for example, a temperature stratification of more than 2°C was reduced to <0.7ºC using 225 W of power. Before mixing, the 3.8 million-L (1 million-gal) reservoir was thermally stratified with an approximately 5ºC temperature difference between the surface and 0.6 m (2 ft) above the tank bottom. The thermal gradient was reduced to less than 0.5ºC within 12 hours of mixing, using less than 200 W of power.
The company is preparing to beta-test the product with several large municipal utilities in anticipation of commercial release late this year.

For more information, contact Mary Hansel at (925) 932-1710.