Harmful Algae - 12 Pages

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Harmful Algae

Catalog excerpts

HOW TO STAY AHEAD OF THE BLOOM xylem Let's Solve Water

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Harmful Algae: How to Stay Ahead of the Bloom It's the call no water treatment plant superintendent wants to receive, especially not while on vacation. Andy McClure, Superintendent of Toledo, Ohio's Collins Park Water Treatment Plant, answered his phone to hear his head of operations report that the level of microcystin in the finished water was high, caused by a large harmful algal bloom (HAB) that was impacting the plant's Lake Erie intake. Microcystin is a common and very potent toxin created by blooms of cyanobacteria, also known as blue-green algae. At 2.5 pg/L, the level was more than...

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Taste and odor also caused by HABs – leading cause of customer complaints Even without the looming toxicity concerns, HABs can be a public relations nightmare for your utility due to taste and odor. Some cyanobacteria that create toxins also create Geosmin and 2-Methylisoborneol (2-MIB), causing earthy, musty smells detectible at very low levels – 30 ng/L for Geosmin and 5 ng/L for 2-MIB. Like most cyanotoxins, these compounds are released when the algal cells die. Also like cyanotoxins, these compounds are not removed through conventional filtration. Though not technically harmful, taste...

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Table 2: World-wide guidance on cyanotoxins A listing of other countries can be found in the Global Water Research Coalition, International Guidance Manual for the Management of Toxic Cyanobacteria, 20 097. In addition, the EPA has added three cyanotoxins, Microcystin-LR, Anatoxin-A, and Cylindrospermopsin, to the Third Contaminant Candidate List (CCL3). The Fourth Unregulated Contaminant Monitoring Rule, UCMR 4, also requires monitoring for ten cyanotoxins at all large (more than 10,000 retail customers) and 800 randomly selected small Public Water Systems with surface water sources or...

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Figure 2: Factors contributing to HABs The concentration and duration of HABs will likely increase, as temperatures and carbon dioxide levels rise due to climate change and watershed development increases nutrient loadings. Through transport of toxins released into the water, a HAB may impact a utility that is far from the actual bloom. Which raises the all-important question: How do you stay ahead of algal blooms? What are your management options? Management Options The utility has three types of management options to control HABs impact on their utility: 1. Source controls 2. Intake...

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Depending upon the source water, several options (Table 3) might inhibit the algal growth. However, once a bloom has taken hold of a water body it is hard to fully eliminate it, and source control methods usually require repetitive action. It is extremely difficult to remove or prevent the growth of all algal cells. Preventing the entrance of excess nutrients into the system is also very challenging, especially when they may be flowing in from outside, uncontrollable sources. Table 3: Source Controls Case Study: Thames Water - Using Reservoir Profiler to Maximize Water Quality, Reduce Algal...

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For some utilities, intake modifications (Table 4) might keep algal cells and toxins from entering the treatment system. Vertical profiling and good data on the biochemistry of the source water is key to intelligent decision making when looking for a new source or making modifications to an intake. Table 4: Intake Modifications Treatment Modifications For many utilities, source controls or intake modifications are either not practical, or are not capable of ensuring that no algae or toxins enter the system. For those, treatment modifications provide the only viable options. For algae and...

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Table 5: Treatment Modifications Cell Removal Methods: When evaluating removal options, keep in mind the algae's natural buoyancy. This makes removal through settling processes more difficult, requiring more chemical to force the algae to settle. Also, with algae's sticky texture, it can quickly blind strainers and filters. Because of these properties, DAF is often the best alternative as it takes advantage of the buoyancy and can remove the algae without lysing or blinding. Compound Removal Methods: In most cases, removal of the algae alone will not remove the toxins or taste and odor...

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How do you know when to begin treatment? Monitoring is the first line of defense. Recent advances in monitoring technology can help you stay ahead of algal blooms. By knowing if the conditions are right, and if the algae in your surface water supply is indeed cyanobacteria, you can take steps to mitigate the impacts and minimize liability - at a minimal cost by not treating when you don't have to, or if there is a bloom, possibly using technology to locate and access raw water with lower concentrations of algae. So, what should you monitor? The best monitoring strategy is two-fold: Both in...

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Table 7: In water monitoring Many of these parameters are self-explanatory, monitoring conditions that either favor algal formation or may be indicative of the beginning of a bloom. Remember that timing is critical, so in-situ monitoring is essential - you must know what is happening in real time. One vital link is determining if an algal bloom is indeed blue-green algae. Thanks to advances in sensor technology, which measure fluorescence to distinguish between green and blue-green algae, this determination can now be made in real time. Real time identification allows you to be proactive in...

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Putting it all together – the four-point plan. Step 1: Protect and Gather • Protect your watershed from nutrients: Engage stakeholders such as agricultural producers to avoid overfertilization. Regulate development to minimize nutrients in stormwater discharges, septic systems in rural areas, and upstream wastewater plants and other point-source dischargers. These options are often beyond a utility’s direct control, but can be much more economical than future investments to address blooms. Gather information: Implement a monitoring program to gather data on water and environmental...

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