Versatile Aqualog saves chemical costs at treatment plants

The primary role of a drinking water treatment plant is to provide clean drinking (disinfected) water.

The largest expense for most drinking water treatment plants is the chemicals to remove the natural organic matters that come into the soil. There are large fluctuations of its concentrations and can change by orders of magnitude in a day, depending on a rain event, a snow melt, or a wastewater discharge. The scientists who run the plants have to be able to adapt and adjust their chemical dosing.

The main reason they add these chemicals is to remove this organic matter, because when the operators add the disinfectants at the end of the treatment process, it reacts with the organic matter and can cause a variety of harmful effects, which are sometimes known to be carcinogenic.

HORIBA Scientific’s Aqualog spectrofluorometer, which measures absorbance spectra and fluorescence Excitation-Emission Matrices simultaneously, gives the plant operators an instantaneous reading of this dissolved organic carbon concentration, and more importantly, its composition. And the Aqualog does it 10 times faster than the nearest competitor.

“You can save up more than a quarter of a million dollars, or $300,000 a year of their $3,000,000 annual chemical budget,” Aqualog Product Manager Adam Gilmore, Ph.D. said. “It means that the Aqualog would pay for itself in just a few months.“

The Aqualog, which incorporates a CCD fluorescence emission detector, has another important advantage. Most water treatment organic laboratories make daily measurements of dissolved organic carbons to keep track of their online monitoring systems, which use generally much simpler types of detectors. These detectors lack the depth of information needed to monitor their system. The Aqualog has a speed advantage in that you can make organic carbon or formation readings in just two or three minutes per sample.

Other systems take 20 to 30 minutes to make these measurements, and require a separate absorption measurement to get some idea of the composition. The Aqualog measures both absorption and excitation at the same time.

“The Aqualog is the fastest scanning florescence system available,” Gilmore said.

“We have customers who take hundreds of samples a day and they're always measuring the absorbance and the fluorescence at the same time. The issue is they are primarily limited by their sample preparation. So the biggest complaint about the Aqualog is that it measures faster than they can generate the samples.”

An accessory “sipper” attachment is available for the Aqualog to take multiple sample measurements more efficiently.

Geoscientists and geophysicists tend to focus on environmental issues. Dissolved organic matter is present in the ocean and large bodies of water locked up in sea ice and tundra. This dissolved organic matter is expected to increase with global warming or sea ice melting. The Aqualog has been used in many studies of this phenomena in the Arctic and in Antarctica.

Hydrologists use the Aqualog for a number of purposes. It can fingerprint specific sources of organic matter, as well as tracer dyes released in a different area to measure how the material migrates. Another type of application looks at a sample’s natural organic signature to say whether it is from a terrestrial or marine origin, and whether it's being influenced by microbial activity or others, or associated with waste water sources.

Environmental researchers use the Aqualog to detect oil and oil products that are soluble in water. These instruments were used in the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. It’s also being used in Alaska to monitor the water quality from the Exxon Valdez oil spill that occurred in 1989. The oil signature from any type of spill is unique. The Aqualog gives you a very distinct fingerprint of that oil contamination, so you can use it to track its geographical source and its composition.

Soil scientists and microbiologists study how dissolved organic components seep into our water sources. A large component of the organic matter is broken down by microbes and forms other components of organic matter as it’s breaking down. Scientists use the Aqualog to study these occurrences.

The Aqualog can be used also to study planktonic algae and algae blooms, identify different species of algae and track trends in the algae population as well. Algae can affect the taste of drinking water, form toxins and be harmful to aquatic life.

“After a large bloom the algae will die,” Gilmore said. “It sinks to the bottom and then consumes all the oxygen and creates a dead zone. And that's actually what's happening now in Lake Erie. That area is going through a sort of a second death. It died in the late sixties and seventies and then recuperated. It’s getting worse again. There's wastewater that goes in, and wastewater contains a lot of microbial and algae-available substrates. And there's also fertilizer, including nitrates and phosphorous that get in the water and fertilize these blooms.”

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