Quick Count

An instrument enables a water plant in Colorado to monitor algae, zooplankton, and zebra mussel veligers simultaneously
Quick Count
Cline uses an automated FlowCAM particle imaging and analysis system from Fluid Imaging Technologies.

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In 2007, snowmelt and a wet winter sent unusually high levels of nitrogen and phosphorous into Standley Lake, a 13-billion-gallon reservoir in Colorado that provides water to the Cities of Westminster, Thornton, and Northglenn.

“We weren’t expecting problems because after the initial flush, the water becomes very clean,” says water treatment analyst Kelly Cline at the Semper Water Treatment Facility in Westminster. “Furthermore, our zooplankton population peaks in mid-May and controls algae blooms even with incoming nutrients.”

Nevertheless, this time an algal bloom did occur. The city responded with a new instrument that detects multiple species of microorganisms at the same time and now provides early warning against such events.

 

Manual process

Before the advent of the new technology, city laboratory personnel sampled the 73-foot-deep reservoir every two weeks and used microscopy to analyze algae populations. Technicians spent three to four hours manually counting the organisms in one or two strips out of 20 in the counting cell. The tedious, monotonous process left results open to interpretation.

By the time water operators realized there had been a massive algae bloom and dieoff, the pungent odor from the organisms had entered the distribution system. Customers began calling. Operators immediately oxidized the water, and the problem disappeared in one week.

“Odor usually doesn’t make it through the treatment process, but this time it did because of the type of algae — Stephanodiscus,” says Cline. “I suspect we didn’t have a good zooplankton population, enabling the algae to gain the upper hand and catch us off guard.”

The event and the threat of blooms blocking filters or pumps convinced officials that they needed a more accurate, faster monitoring system. Cline searched the Internet and found the automated FlowCAM particle imaging and analysis system from Fluid Imaging Technologies. The instrument enables him to analyze a complete counting cell in 10 minutes and process the data in 20 minutes.

 

Invasion force

The Semper facility treats 44 mgd using conventional filtration. The Northwest Water Treatment Facility treats 15 mgd using membrane microfiltration. Westminster’s 111,000 residents use 18 mgd on average with a peak of 44 mgd.

The urgency to upgrade the monitoring system was compounded in 2008 when biologists found zebra mussel veligers (larval stages) in Colorado lakes. Cline contacted company representative Harry Nelson, director of aquatic markets for Fluid Imaging Technologies, and asked him about adding cross-polarized illumination to the instrument.

“Veligers fluoresce when passing through polarized fields,” says Cline. “We wanted to look for algae, zooplankton, and veligers simultaneously.” The engineers were successful, the city purchased the unit, and Cline took over analyzing water quality.

Company representatives set the camera speeds, distance between particles, and other protocols, then gave Cline two days of training. “Technicians with the knowledge of different algae types will find the instrument easy to run,” he says. “Those without it don’t need to identify everything to a genus-species level. Just looking at the most numerous algae will tell them the dominant species, which is most likely the one causing the problems.” Cline has not changed any of the instrument’s original settings.

 

Three-in-one instrument

Cline uses a Secchi disk to measure water clarity in the reservoir and also runs weekly pipeline samples. The latter helps him gauge algae conditions when the lake is iced over and water temperatures are identical from top to bottom.

“As what is growing in the surface layers dies, it falls out as ‘snow’ and then is captured through the pipeline,” he says. “The lake also has chlorophyll a probes (YSI). If we notice an increase, we collect samples immediately.”

The benchtop analyzer has a microscope with 4X, 10X, and 20X magnification, high-resolution digital camera, and a counter that measures particles from 3 microns to 2 mm. “Our problem algae are 25 to 300 microns, so I don’t spend much time trying to identify 5- to 25-micron algae,” says Cline.

The instrument automatically measures particle and microorganism size, length, width, shape, equivalent spherical diameter, and fluorescence in real time, then saves the data for analysis. In 10 minutes, Cline has some 15,000 images. Pattern recognition software lets him sort the data in minutes and match detected cells against known nuisance algal cells for identification.

 

Rave reviews

“To have something capture images of everything I see on a slide with reproducible results is amazing,” says Cline. “To sort that information based on size, shape, color and whatever is incredible. Having a permanent record of the analysis is a first for us and very exciting, because now we have a database for trending analysis, forecasting, and graphing.”

Cline advises water-quality laboratory technicians not to be afraid of the technology and counsels management not to get bogged down by the cost: “If the instrument helps to prevent or minimize an algae bloom, the money saved in not reacting after the fact, and the loss of customer confidence in your product, will pay for it.”

Water operators have since installed an odor-control system that measures oxidation reduction potential (ORP). If the ORP changes, they feed more sodium permanganate to neutralize odors. The city initiated one of the strictest boating policies in the state to stop zebra mussels from invading the lake. Cline looks for veligers as a precautionary measure.



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