Hypochlorite Feed System 1

[zedias]

Hi. I'm new here...I just start working on a wastewater plant in Portugal and I've got to implement a hypochlorite feed system, to add chlorine in the water, to assure a secure chlorine residual of 0,2-0,5 ppm.
I saw thread164-78627 in the forum but I couldn't ask there because the thread was in archive, so I'd to create another one with same subject.
I'd like to know what all of you think about it and help me to know what's the best way to do this system (equipments, etc).
Thanks.

 

[bimr]

Everything has already been addressed in that thread unless you have a specific question.

 

[zedias]

Thanks bimr for the response...but I need to know everything abou the system. I mean, valves, pumps, materials and any other equipment needed.
As I said, I'm just starting my work in engineering because I just left the University a small weeks ago.
For now, I know that I'll need a reservoir and a retention tank for hypochlorite solution, but I don't know what's the best material to do that. Another question is the valves and control systems, I mean the chlorine control (PID) and the pumps that will be needed.
Can you help me with this? Do you have any documentation about something similar?

 

[bimr]

This specification may be of some help to you. If it does not answer your questions, post again.

http://www.odysseymanufacturing.com/bleach_information.doc

 

[zedias]

Thanks again bimr. This is real what I need...it's this kind of information that I need to start the design of the system. Thanks a lot. Now I just have to know what come after the hypochlorite reservoir, you now, some kind of static mixer and injectors and dosing pumps. Can you tell me how can I found some more information about that?
Thanks again

 

[DMcGrath]

Good information in the thread listed regarding the degradation of the hypochlorite solution. I have a client in Florida (USA) that the strength of their NaOCl solution goes to about half over a month's time of sitting in the Florida heat.

As far as the injection system you need help with, a lot of the design depends on what you have already. Usually hypochlorite is injected into the water stream early, before any storage or pressure tanks. The mixing action of the water in the tank usually takes care of the distribution of the hypochlorite and gives it a sufficient "residence time" to act. If you can get 30 minutes of residence time in your tank (volume / flow rate) and are confident the flow is not short circuiting from inlet to outlet, then that will probably work for starters.

The amount of hypochlorite and the pressure to pump it in depends on the flow and pressure of your system into which you are pumping. Pumps I have seen have been Pulsafeeder or LMI pumps, which are typically designed for this kind of service. I think Pulsafeeder even sells package systems with a tank and everything.

Other than that, you will probably want some form of feedback to control the pump output. Again, the pump suppliers can provide this for you.

 

[zedias]

Thanks again for your answers...well...I've contacted a manufacturer here in Portugal to install the system in the reservoir, but he said that is not possible to install a static mixer there, because there's not enough flow. The mixer was to install on the exit pipe 300 mm, with 1 Bar and a flowrate of 206 m3/day.
Any of you know any other way to do the mixing? Is any other eficcient method to do it? Any sugestions???
Thanks again.

 

[orenda1168]

Zedias:

Install your hypochlorite injection just upstream of the last control valve/shutoff valve ahead of the tank, or into the suction side of the water pump feeding the tank. Either method will ensure suitable mixing.


Orenda

 

[zedias]

Hi again. Prominent dealer in Portugal gave me a proposal with some kind of submersivel pump inside the tank to promove the mixing directly there. Any of you knows anything about this kind of method? The system is quite simple. There's no need of static mixer. It consists of one diaphragm dosing pump, which is connected to the HYPO storage tank and sends the HYPO to water tank. In this tank will be installed a submersivel pump that will constantly (24 hours/day) analyse the chlorine residual in the water, and if there's not enough chlorine it will send a signal to the chlorine controller to inject more chlorine. Well, my doubt is if this method is adequate to do the rechlorination with HYPO. The dealer here in Portugal says that is a good method to do it, because it saves money, but I really don't understand how they do the mixing in the tank???? Any of you knows something about this?

 

[bimr]

Maybe you can explain what you are trying to do.

You are working in a wastewater treatment plant. Correct? You want to add chlorine? The purpose of the chlorination?

What is the chlorinated water going to be used for?

You want to add hypochlorite storage tank, yes, or no? This tank should probably hold 1 1/2 of the delivery truck volume.

Is this a municipal wastewater treatment plant?

What is level of treatment in plant? Secondary, advanced, etc.

 

[zedias]

Yes, I'm working in a municipal wastewater treatment plant. The chlorine residual that lefts the treatment plant is 0.2-0.5 ppm. Well, as the water goes for the consumers there's a chlorine decay, and in some points of the "net" the residual is 0.1 ppm or less. To assure that there's a minimum of 0,2 ppm of chorine I need to instal a rechlorination station in a reservoir far from the treatment plant. I just wonder what is the best way to do it. Initially I read the document you told me and I'd proposed something similar to do here. But there was a problem with the static mixer, because the manufacturer said that there wasn't suficient flow to do it. Then it considered another method, wich consists on a submersive pump to do the mixing directly in the reservoir. The system analyzes the water continuosly, 24 hours/day and control the chlorine residual to give the indication on the controler to inject more chlorine, by the use of a diaphragm dosing pump in the HYPO storage tank.
I'd like to know if any of you have ever heard something about this, and your opinion about it. Thanks.

 

[bimr]

What is the size of the reservoir?

What is the water used for?

 

[zedias]

bimr, the reservoir has 2 cells with 250 m3 each and the water is for municipal supplying.
I just don't know if the mixture inside of the reservoir is efficient...I don't think so...
Thanks for your interest

 

[bimr]

My understanding is that you have a water reuse tank 500 m3 capacity divided into 2 cells that is holding treated municipal wastewater. You want to boost the concentration of chlorine by adding hypochlorite.

The method that you have proposed with a submersible mixer will work and has been used successfully.

The submersible mixer should have power of approximately .5 kw per tank. You also need the hypochlorite storage tank, pump, and controller.

An alternative process would be to use a pump mounted outside the tank to recirculate the tank contents.

Since you are just blending in a liquid, you do not need high energy mixing.

 

[zedias]

Hi bimr. I hadn't seen your reply... Do you mean 0.5 KW per tank or 5 KW?
About the alternative method...what's your sugestion?

 

[bimr]

It should have said .5 kw per cell. You do not need much mixing energy for what you are trying to do.

The alternative would be to use a pumped recirculation. The pump would take suction from one side of the tank and pump it to the other side. You can add the hypochlorite inline on the discharge side of the pump. With a pumped system, you would not have to drain the tank to do the installation.

 

[zedias]

Sorry bimr, but I didn't understand what you are trying to say...you mean do the recirculation from one cell to other, or inside one cell ????
With submersible pupms there's no need to drain the tank either.

 

[bimr]

With submersible pumps or mixers, you have to drain the tank in order to fasten the equipment to the tank, at least initially. Mixers are usually fastened to a pole that is attached to the bottom and walls of the tank. Submersible pumps are fastened at the base to the tank floor. You will also have to make a stairway and platform if your tanks are elevated off the ground.

One thing that you might want to think about is the problem of pumping hypochlorite. Most users have had bad experiences because the hypochlorite is hard to pump because hypochlorite will off-gas, and is also very corrosive when it leaks.

The recirculation system will take suction from one tank cell or both (with a manifold) and pump to the opposite end of the tank or tanks. The pump would force the water through an eductor that would also be used to inject the hypochlorite. Portacell makes a hypochlorite injector like this. You need to have a 20-25 psi drop across the injector to inject the hypochlorite. With an inductor, no hypo pumps are needed.

http://www.portacel.co.uk/welcome.htm

The recirculation system is probably more user friendly and reliable.

 

[zedias]

Hi again...I think we are talking the same method of recirculation. When I meant sumbersible pumps it means that the pump will be located in the tank to recirculate, and not to pumping HYPO, the hypochlorite will be pumped with a dosing pump located outside the tank...
Well, it's not easy to explain, so I think it's better to send you a scheme with the instalation.
How can I do that?

 

[bimr]

You can send something to twentyzip2ATyahoo.com