The Common Problem of Struvite
Also known as magnesium ammonium phosphate, Struvite can develop quickly and its crystals can grow like weeds until it all but shrinks the flow area in a pipeline to nothing. It is A common occurrence in wastewater treatment plants and can quickly get out of control. When the conditions are right it will rapidly form crystals that spread throughout a pipeline forming a concrete-like crust. It is most commonly a problem in dewatering filtrate or lagoon decant and in spots with local turbulence, such as pipe elbows, mixer blades and pumps.
Struvite can become debilitating if left unchecked. Like cholesterol coating the walls of vessels and arteries, Struvite can reduce flow area significantly, severely restricting flow and reducing pressure. Struvite can damage equipment, especially valves, when the valves close it rips the rubber faces of the plugs stopping the ability to shut valves tightly.
When Struvite Occurs – Real-life example: Madison Metropolitan Sewerage District
The Madison Metropolitan Sewerage District in Madison is a large plant that treats over 40 million gallons of wastewater a day. Its massive compound has 120 miles of interceptor sewers and force mains, and it boasts over 100 pumping stations.
They had experienced Struvite forming in digested sludge lines and plug valves. Presence of Struvite not only restricts flow and damages valves but also requires frequent, laborious maintenance, which is what the employees at the Nine Springs Wastewater Plant learned.
They had already experienced some maintenance issues as a result of Struvite accumulation. Struvite would normally build up on the inside of piping and valves, causing a reduction in flow. This necessitated disassembling the piping system to chisel the Struvite from the piping and valves.
How to Combat the Problem of Struvite:
The Madison Metropolitan Sewerage District partnered with engineering firm Black & Veatch along with mechanical contractors J.F.Ahern Co to attempt to combat the problem. They discussed Madisons history of Struvite accumulation within their digesters and associated digested sludge piping and valves.
They decided on the solution of installing glass-lined plug valves which are easy to install. Glass-lined plug valves were chosen because the glass lining provides a smooth, non-stick, interior surface that helps to prevent the collection of elements that lead to a Struvite build up in a location that’s known to be a likely problem area. They will also cut down on friction loss.
Valmatic Producers of Glass Lined Plug Valves
Glass lined plug valves were not readily available as a coating option so they turned to Valmatic for help. Glass lining is a highly specialised option and Valmatic are one of the few manufactures that provide glass lining for all sizes of plug valves. Over 20 of Valmatic glass lined plug valves were installed at Nine Springs Wastewater Treatment Plant.
Other Methods for Solving Struvite Problems involve chemical control, which is costly and requires regular maintenance.
Therefore, choosing glass lined plug valves at an area prone to Struvite growth is the best option to consider.
If you can relate to the issues discussed in this case study