Would this work? 1

[hblock72]

I currently have a water header over a waste conveyor and I'm looking for ways to reduce water usage. This header is ~600 feet of 3" schedule 80 pipe suspended above the conveyor. Along the 600' length are 3/4" drops (approximately 20 of them) that put water into the conveyor. There are no spray nozzles, just open 3/4" pipe discharging into the conveyor. These drops do have manual valves to allow the flow into the conveyor to be adjusted at each drop. The header is fed from the municipal water supply at ~60 psi. The water is turned on and off via a solenoid valve on a timer that coincides with the conveyor run time (30 minutes on/30 minutes off). The flow rate through the header when valve is opened is ~125 gpm. The water passes through the conveyor and is collected in a series of floor drains and gravity flows to a water treatment plant via three different catch basins.

I would like to install a pump at one of the catch basins and recirculate some of the water back through the header to reduce the amount of municipal water used since we're paying for every gallon that goes through this conveyor. My thought is to use a 35 gpm pump sucking out of one of the catch basins and feeding it back into the beginning of the main header. I would use a flow control valve to maintain the 60 psi in the header using the municipal water supply. My hope is the small recirculating pump would pump as much as it could into the header and the rest would be made up by the municipal water flow via the flow control valve. There would also have to be a float switch in the basin in case it were to pump it dry the re circulation pump would shut off in which the case the header would be fed 100% from the municipal supply, just as it is now. I'm concerned if this is even possible or will the two flows be constantly trying to deadhead one another? There would also have to be a check valve installed in the municipal supply line to prevent any back flow of non potable water. Thanks in advance for your input.

 

[chicopee]

My thoughts would be: 1)install a trough under the conveyor to collect as much water flowing thru the conveyor 2) have a storage tank to accumulate all water collected from the trough 3)filter and chemical treatment the collected water before it is redirected to the conveyor. Cost of my proposal would be high but in the long run , there COULD be a payback on your process. Don't forget that the cost of municipal water is the water itself plus the extra amount for pollution controls mandated by the Feds. Municipal water is no longer cheap.
The question is at what pressure will the delivery of 35 gpm be achieved? Also provide a hand sketch of the proposed set up. The sketch should include elevation differences and a plan view with piping, valves, pumps, and water supplies from municipality and proposed 35 gpm pump.

 

[mk3223]

It sounds like a good project to improve the operation cost and environmental conservation, and it's feasible plan.

First, you may make a basic sketch of the system as described, and then add in the detail control elements as desired. For your thoughts, here are some elements on the system, such as:
- a main water line on the conveyor with a flow control to the municipal water supple valve,
- a pressure control valve on the recycling water line per main supple line pressure,
- a back flow preventer required on the municipal water inlet line
- a waste water treatment tank to filter the recycling water for reuse

 

[miningman]

I think I would want to know what material is being conveyed, which would then lead to questions of likely solids % in the reclaim water, eventual disposal of slime, any liklihood of freezing conditions, etc etc

 

[LittleInch]

The municipal supply won't like this and will have some strict requirements and regulations to prevent backflow of your dirty water back into the city supply.

You won't need a flow control valve on the supply. Just pump your water back inot the header. As it's less than the total you use which is controlled by your nozzles the city supply will automatically male up the difference (approx 85 gpm)

My concern would be oN the quality of the reused water. I suggest a filter at the least or some sort of settling pond.

At that level of flow percent in terms of reuse you should be ok in terms of the water getting more and more dirty.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[danschwind]

You could also consider the route of installing 2x 125 gpm pumps (to allow maintenance), a large enough tank to hold all the water you need during the 30 min conveyor run time, some level controls in the tank (so you can top off the level with the municipal water) and some filtration system.

 

[hblock72]

Thanks for the replies. My original design did incorporate a holding tank to pump the recirculated water to. This allows me to capture water even during the conveyor off time and will give me greater flexibility in how much water I choose to re-circulate. I will also have a municipal water make up supply to the tank to a)make up any shortfalls of reclaimed water if any and b)add some fresh water to the system to avoid chemical treatment. The water that goes through the conveyor is relatively clean as it is only conveying scrap fiberglass and the water is mainly used as a lubricate to help the waste fiberglass slide along the conveyor. I plan to pull the recirculated water through a duplex strainer that will be located before the sump pump.

The idea of pumping the re-circulated water directly to the header was for a less expensive approach as it eliminated the need for a tank and used one pump vs. two, but it just won't be as effective so that idea has been dropped. By using the tank and having a municipal water make up to the tank, I can avoid having to worry about mixing them both directly at the header. In fact I plan to completely valve off the municipal supply at the header and it will be used as a redundant backup system. Thanks again.

 

[Compositepro]

A single block valve is not adequate as a back-flow preventer. You must have an air gap, which may be at the top of the tank where the water is added or by using a back-flow prevention valve.

 

[hacksaw]

There must be a significant "air gap" per your local water codes.

you are better off putting drinkable water in the recycle pit, and pumping that.