Struvite Removal

Vivianite Heat Exchanger removal trial case study


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On the vivianite-laden heat exchangers, the maintenance supervisor created a recirculation circuit and diluted JS 9325 to a fifty percent (50%) solution. They recirculated the diluted solution for 48 hours while raising the temperature of the solution to 110F. Upon opening the first heat exchanger, they observed a purple solution following by a half-inch (½”) sheet of vivianite scales popping off the surface of the heat exchanger. They made up another solution and repeated the cleaning cycle. After the second cleaning, they returned the heat exchanger back to service. They were able to heat the digester and control the temperature while reducing their heating cost.

As a result of using JS 9325, the screw press operation improved due to cleaner screens. They had a drier cake using less polymer per dry ton. The operation of the digester improved based on operating at a higher temperature. The plant saw an increase in methane generation. The sludge from the digester dewatered easier. The spent solution was comprised of iron phosphate, magnesium phosphate, ammonium phosphate, chelated magnesium and simple sugar compounds, which was discharged to back to the headworks of the plant. This spent solution is highly biodegradable. There is no major drawback from extra handling or offsite disposal, which other acids or removers can require.

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