Hello everyone, I'd like to know which pump brand/model/type is the most suitable for a continuous feeding to a wastewater treatment plant. I'm talking about very low flows, starting at 5 liters per minute, and also low working pressure, not more than 1 bar. One way I've solved this problem is by-passing the feed just in front of the pump and sending it back to the equalization tank.
Any information about low flow and low pressure wastewater pumps is very appreciated. Thanks in advance
You may also use submersible pumps according to your nature of waste and the solids in it. Make sure you installed a proper flow meter in the discharge point. After all I`m so agreed with Yerman Saavedra about using drives and saving the energy.
I believe some information is missing here. What is your range of desired flow? (you only mention a starting point of 5 l/min), What is your dynamic head?. Do you have VFDs? (Variable Frequency Drives). Do you control the level in your equalization basin or just the incoming flow to 5 l/min?
In any case, you should take a look at the point of discharge of this system (a system curve would be great) and see if your existing pump is operating within its curve, otherwise you might be operating it in a very inefficient zone, or perhaps your pump is oversized.
If you ask me, for wastewater you want a pump with two vane impeller, capable of passing 3" sphere (depending on pump size, although I figure this is a very small pump) and of the self-cleaning type (such as Flygt with N impeller). If wastewater is already screened, you don't need a self-cleaning impeller because the risk of that pump clogging is minimum.
Returning part of your flow back to the equalization basin is giving you the hardship of consuming more energy without truly conveying any flow to your final destination, reason sufficient to get a VFD, and you'll see your energy cost dropping significantly (see affinity laws).
I’d suggest to use peristaltic pump and use valve or increase the height of pipe downstream the pump to regulate the pressure. You can use PRV but note that there is a risk of being clogged and solid deposit formed which will deteriorate the PRV performance although you install strainer at the PRV inlet.
If you have solids or rag in the wastewater (likely) then a centrifugal pump won't be reliable at such low flow rates. The openings are too small.
If you want a reliable pump for low flows with solids present, use a peristaltic pump. It will generate more than 1 bar but if this is a problem you could fit a pressure relief valve or 10m high overflow pipe. Peristaltic pumps are not cheap though.
Use a peristaltic type of pump, try verdiflex or similar. Wheels will push waste water no problems. make sure coarse strainer on suction or screen used in collection tank.