Water Environment Federation (WEF) Discussion Forums / Disinfection / Archives / Archived Forum Topics

RE: chlorination and fire/mech code

TerryF — Sun, 17 Feb 2008 16:04:37 GMT

David,

You are right. However i think the sprinklers are mainly there to limit the fire around the chlorine containers and thereby limiting the damage. Likewise if there is a leak the water tends to convert the chlorine to hydrochloric acid as you suggest but at least this is in a liquid form that might be able to be contained unlike the gas which will drift off downwind.

Regards

TerryF

chlorination and fire/mech code

01763398 — Wed, 25 Jan 2006 11:01:41 GMT

We are currently designing a new chlorination building for a rural water system. Our mechanical/electrical guys are saying (based on current International Fire Code and Mechanical Code) that we need to continuously ventilate the room where the gas cylinders are located AND install fire sprinklers. Our building will be concrete/masonry and steel so there are no combustibles located in the chlorine room. We'd like to do intermittent ventilation and eliminate the fire sprinklers. Does anyone have RECENT experience dealing with these issues? Have building/fire officials allowed variances?

RE: chlorination and fire/mech code

D Shulmister — Sun, 17 Feb 2008 11:15:55 GMT

If I recall correctly, putting water on a chlorine leak will produce hydrochloric acid which in turn will eat away around the leak area and cause it to grow.

RE: chlorination and fire/mech code

Christopher Buckley — Tue, 12 Feb 2008 12:27:49 GMT

Chlorine can support combustion, so yes, sprinking is often required by fire code, along with a host of other safety and monitoring equipment for chlorine gas like ventilation

Not sure where you are but I would bet good money that no permitting agency (environmental or fire) is going give variances on chlorine gas Risk Management Practices. It's why most agencies have moved to other forms of chlorination.

RE: bioassy motality using sodium bisulfite

Rob Baur — Tue, 05 Feb 2008 12:42:09 GMT

We use a feedback loop using an on line analyzer like http://analyticaltechnology.com/cms/Default.aspx?tabid=89 It is relatively cheap and uses diluted sulfuric acid as its only reagent. Be sure to install a system to bleach the sample lines automatically as bisulfite residual will grow slime that consumes both bisulfite and reacts with chlorine.

Bisulfite does have a BOD, but chemical DO consumption requires a catalyst like cobalt. Old Std. Mthds. had an aerator test that depressed the DO by adding bisulfite and a cobalt catalyst. Measuring DO drop due to bisulfite on the lab bench showed a DO increase due to the DO probe stirrer. Adding a catalyst dropped the DO immediately.

bioassy motality using sodium bisulfite

Phil — Fri, 01 Feb 2008 11:51:06 GMT

All,

During our dechlorination agent conversion from SO2 to Sodium Bisulfite,WET bioassay monitoring was conducted with a >50% mortality to the Mysid Shrimp. The lab feels it was due to a overdosing of the bisulfide because only the shrimp was effected which I agree. Anyway, does anyone have experience with the bisulfite dosing? IE enough for chlorine removal but not overdosing.

Thanks,

Phil

RE: bioassy motality using sodium bisulfite

rwhitworth52 — Fri, 01 Feb 2008 13:43:00 GMT

Phil,

You are most likely correct about maintaining the D.O. during the toxicity test procedure; it just came to mind about the D.O. depression.

RE: bioassy motality using sodium bisulfite

Phil — Fri, 01 Feb 2008 12:24:11 GMT

Thanks! I thought DO was monitored & controlled at a level of >4.0 mg/l during the 96hr test period.

RE: bioassy motality using sodium bisulfite

rwhitworth52 — Fri, 01 Feb 2008 11:57:40 GMT

Phil,

Using bisulfide for dechlorination is usually 1 part to 1 part. Excessive use of bisulfide will deplete oxygen and kill the test organisms.

RE: Breakpoint Chlorination

Woodie — Thu, 31 Jan 2008 20:20:42 GMT

Ryan,

The following is a quote from EPA's Nitrogen Control Manual:

"The utilities director's recommendation for other considering full nitrogen control by breakpoint chlorination can be summarized in one word --'don't'. "

It is not a stable reaction. If you use elemental chlorine you will likely need to add alkalinity to ensure a complete reaction. If you use hypochlorite you won't.

Clifford White's Handbook of Chlorination would be your best source of information.

Woodie

Breakpoint Chlorination

WasteWater TREATOR — Thu, 31 Jan 2008 16:40:40 GMT

I need to calculate the correct dosage for reducing ammonia from approximately 100ppm to 20ppm through breakpoint chlorination. can anyone help me with this calculation? I cant seem to find it...and i need the dosage per gallon of wastewater...

Ryan

RE: Breakpoint Chlorination

rwhitworth52 — Thu, 31 Jan 2008 17:16:43 GMT

Ryan,

Try feeding 8 parts chlorine per part of ammonia. If you want to remove 80 mg/l ammonia you need to apply 640 mg/l of chlorine. 1 % soluiton of chlorine is equal to 10,000 mg/l. If you want to know exactly how much to feed, volume of water to be treated and % of available chlorine is needed (if liquid is used). This is just a starting point because other materials can consume chlorine.

RE: Chlorine Contact Tank Dynamic Control

01780898 — Thu, 24 Jan 2008 07:25:53 GMT

David

We are thinking about a spray header and perhaps aeration mixing to rechlorinate the first pass(es) of the tank.

Alternatively we are looking at a recirc system to recirc the outlet back to the inlet and rechlorinate the flow, until the residual rises and we can discharge

Chlorine Contact Tank Dynamic Control

01780898 — Tue, 04 Sep 2007 23:49:18 GMT

We have designed a chlorine contact tank for a reuse application. The plant is a BNR plant with low ammonia and P. Due to the low ammonia we designed to chlorinate to produce a free residual, reducing tank size over chloramination. The tank presently has a Tmean 71 min and t10 estimated at 47 min.

The health department requires 0.4 mg/L free residual at the outlet. We however note that if the flowrate is reduced, the outlet residual is reduced, for a significant period (due to det time increase and resulting HOCl decay). We are trying to model the situation, to see the extent of the problem.

Has anyone experience in this situation which would resolve the problem without increasing our inlet residual?

Thanks

Grant H

RE: Chlorine Contact Tank Dynamic Control

D Shulmister — Wed, 23 Jan 2008 14:23:19 GMT

Grant

Is it possible to put a second chlorine feed point half way to the effluent weir? Perhaps activated by a (low) flow signal?

RE: UV disinfection enhancement using Ozone

Grant H — Wed, 23 Jan 2008 02:48:28 GMT

Ozone is a very costly process and I suspect there would be better processes to meet your requirements. The two most cost effective are chlorine and UV disinfection.

Do you know why your UV system is not performing. The lamps need to be changed at the specified hours run. Any lamps out will significantly affect performance. The sleeves need to be cleaned on a three monthly basis (unwiped) or six monthly basis for the wiped system (and you need to ensure the acticlean system is in good working order, every six months). On this basis the sleeves need to be sparkling clean on cleaning to mildly cloudy when cleaning is required. Take the lamps out of the effluent and rinse with potable water and then allow 2 minutes for the water to run off and the sleeves to air dry. Then observe the fouling. I would recommend 5-10 % phosphoric acid solution for cleaning. Perhaps your Trojan rep can troubleshoot the unit for you.

The effluent quality needs to be suitable for UV to work. Beyond 12 mg/L TSS you will find UV ineffective. This usually results from a problem with your activated sludge system (such as insufficent aeration (SVI>250 ml/g) or clarification. You could troubleshoot your A/S plant or look at installing a filter (sand, cloth media) upstream of the UV unit.

The UV transmittance of the effluent is paramount and I would recommend you take some samples and have them analysed by the lab. If the design UVT value is higher than the measured value then you need to look at having your UV unit resized by your Trojan rep. and then look at further capacity. Things that interfere are colour (numbers greater than 50), TSS (>12 mg/L), COD and iron (> 1.5 mg/L). Colour can be affected by seasonal water supplies with high colour.

For chlorine you need an approriate detention time. A 30 min time at peak hourly dry weather flow is generally required to meet 200 TC per 100 mL. You would need to ensure your outlet residual meets your permit standards. May need dechlorination

As for ozone, you are looking at a lot more complexity and cost.

I hope that I have given you some things to think about.

UV disinfection enhancement using Ozone

01737572 — Mon, 09 Jan 2006 13:42:03 GMT

We currently have a Trojan UV disinfection system. Periodically we experience high fecal counts due to performance issues and must add supplemental Sodium Hypochlorite for control. Has any one used Ozone in conjunction with UV? I am beginning to look at it as a possible enhancement for our system. We have Pure Oxygen available on site.

RE: Chlorine Contact Tank Dynamic Control

Grant H — Wed, 23 Jan 2008 02:21:46 GMT

The plant and reuse scheme is in Victoria Australia. Australia is taking a QMRA approach to setting limits for reuse water based on DALYs. In the case of Class A (unrestricted reuse, but not cooking and bathing) water legislation requires:

E.coli < 10/100mL

Cryptsporidium & Giardia <6 log reduction from raw sewage conc'n

Virus <7 log reduction from raw sewage

Helminths approx 4 log reduction

These standards are unmeasureable and so the plant rely on a HACCP approach of monitoring treatment parameters and residuals, to guarantee that each process is working. It is a very big effort, but the effluent can be guaranteed as to be fit for purpose.

As for the chlorine residual, we are dechlorinating with bisulfite. I have read a paper on IWA's Water Practice that 1 mg/L will just kill the grass.

RE: Tablet/Pellet Chlorinators

Grant H — Wed, 23 Jan 2008 02:08:19 GMT

I agree with tablet chlorinator problems. Also the residual is highly variable (low at low flows and high at high flows). Also the hang-up problem. I would stick with sodium hypochlorite dosing.

There are some things you should know. The dosing pump needs to be sized for the doserate. Do not operate much lower than about 40 % stroke size and have a fair dose rate at all times including low flows. Otherwise the oxygen gas will accumulate in the head and will not go until higher flows and pump rates. Is you hypo tank shaded from the sun?

You should flow pace your dose rate. This can be done by LMI/Prominent/etc. Otherwise you can rig up a run signal from your outfall pumps, to give flow pacing.

Also there are some companies offering degassing pump heads, which should overcome the gassing problem.

Tablet/Pellet Chlorinators

01809607 — Fri, 18 Jan 2008 19:51:56 GMT

Hello,

I am the Chief Operator at a small RBC/Aerated Lagoon facility and we direct discharge our effluent into a river. Our average daily flow is .080 mgd, with an occassional max flow of .200 mgd. We currently use liquid hypochlorite to chlorinate and sodium bisulfite to dechlorinate. I am researching the possibility of switching to eilther a tablet or pellet type chlorinator.

Any advice, suggestions, comments or recommendations would be greatly appreciated.

Thanks,

John

RE: Tablet/Pellet Chlorinators

John Sansalone — Tue, 22 Jan 2008 13:00:03 GMT

The tablet feed systems have been used around here a fair amount. The sticking in the tube has been a problem (apparently, the tablets tend to swell up in damp conditions), but work well enough if the tubes are cleaned regularly. Best application has been with summer camps, etc., where getting maintenance people to do daily chlorine is always a problem. Many of the camps I deal with discharge to trout streams, and the old standard was a crock of hypochlorite, with a drip feed. this would result in wild swings in residual, depending on flow. The tablets have been useful for those types of situations.

RE: Tablet/Pellet Chlorinators

Jerry — Mon, 21 Jan 2008 13:30:39 GMT

Ditto. Stick with the liquid. The tablet holders will clog with slime and debris, allowing the tablets to hang up. Small package pl ants that have no de-chlorination seem to work okay, if you check them daily.

RE: Tablet/Pellet Chlorinators

J.W.Koch — Mon, 21 Jan 2008 12:57:49 GMT

Have used the tablet feeders not sure of the name brand. The tablets tend to get hung up in the tubes, so you have check them daily. It seems hard to keep a consistent cl2 residual with them.

RE: High Chlorine Demand

zaffrulla — Wed, 09 Jan 2008 08:32:04 GMT

hai
Nitrites in the effluent is the main reason for increasing the chlorine demand as we know chlorine is a good oxidising agent when nitrite reacts with chlorine it prefers for oxidation that is conversion of NO2 to NO3 when oxidation is complete then it will will the breakpoint chlorination and finally go for residual chlorine
hence dosing more chlorine to nitrite rich effluent is a utter waste i would advice to see the upstream process and try to concentrate on the nitrification reaction
regards
zaffrulla
Manager -Operations & Process
WEIR ENGINEERING SERVICES
ABUDHABI

High Chlorine Demand

Tom C — Wed, 08 Nov 2006 15:45:29 GMT

I am looking for recommendations on identifying a source in our WWTP which is periodically depleting our residual chlorine. Our WWTP usually adds around 200-300 lbs./day of chlorine. However, over the past several months on Wednesday/Thursday of each week, we add chlorine at a rate of 1,800 lbs./day in order to maintain a proper residual level. We have seen this spike for several months now but have not been able to identify the root cause.

I welcome anyone's suggestions on what chemicals could be causing this problem. We have several chemical plants, steel mill, poultry processors and metal finishers on our system.

thanks

Tom C.

RE: High Chlorine Demand

The House — Fri, 14 Dec 2007 02:26:09 GMT

We are a plant that handles 25 MGD and are going through the same problems you are having. You may want to check with any industries that could be dumping large amounts of waste containing ammonia. Also any new industrila processes that containe polymers or discharges that may be binding up your available chlorine could be happening.

Rich in Kalamazoo.

RE: Chlorine Contact Tank Dynamic Control

D Shulmister — Tue, 11 Dec 2007 15:29:22 GMT

A free chlorine residual is a little much I agree, but potable water does not kill the grass so 0.4 in reuse water shouldn't either. I guess this is what you get if the health dept is controlling the plant. I too wonder which state this is in.

RE: Chlorine Contact Tank Dynamic Control

Dvant — Tue, 11 Dec 2007 12:36:02 GMT

Grant,

Where are you from?

I thought the 23 total coliform requirement for reuse was bad enough, but a free chlorine requirement. Isn't that going to kill the grass? Are they going to make you check for THM's and HAA5's.

Mark

RE: Chlorine Contact Tank Dynamic Control

Rob Baur — Mon, 10 Dec 2007 13:58:40 GMT

Can the solution be as simple as not flow pacing the feed? Set the constant dose for peak flow conditions and as flow drops off the mg/l dose increases due to the constant dose rate.

We maintain a constant reuse system flow and water not sent to customers overflows a weir and spills into the normal effluent channel to mix with the rest of the plant effluent for de-chlorination and discharge. That way the deterntion time in the reuse contact chamber is constant and much easier to operate.

RE: UV disinfection enhancement using Ozone

Rob Baur — Mon, 03 Dec 2007 13:17:07 GMT

When you use hypo is there a residual that need to be dechlorinated? I see where they are dechlorinating with UV, but at 15X the normal disinfection dose. From my expierence of old ozone technology using the equipment infrequently will be a problem, also ozone is an oxidant that will oxidize KI to I2 and show up as Cl2 in the total chlorine test. It is also very toxic to fish as it attacks the gills etc.

RE: UV disinfection enhancement using Ozone

Vsun — Fri, 30 Nov 2007 01:30:36 GMT

Combined Ozonation-UV system would provide a dual barrier disinfection, might be a good fit for you.

RE: x

D Shulmister — Fri, 16 Nov 2007 12:00:54 GMT

Z !!

x

SRB — Wed, 24 Oct 2007 15:27:37 GMT

RE: x

Rob Baur — Thu, 15 Nov 2007 18:23:26 GMT

RE: ORP system question

Rob Baur — Mon, 10 Sep 2007 13:53:22 GMT

What are the SO2 mg/l values you are seeing at the different ORP values?

ORP system question

Dookie — Fri, 07 Sep 2007 16:06:50 GMT

Hello folks, were doing soem trouble shooting on out ORP system and would like some feed back on those who use one for disenfection what in your eyes is an acceptable or normal amout of variance in ORP reads on the dechlor end. Example if you knew a set point of 150 would give acceptable dechlor results and thats what your set point is how far above and below that mark do you see in a typical 24 hour peroid. Here were getting typically + - 30 MV either way when its running good but have seen swings of 100 MV above our set point which isnt acceptable for permit maintaining results. Set the value significantly lower and we overdose with Bisulfite and the result is poor B.O.D. results due to 02 depletion from excess S02.

Thank You for any feed back you can offer.

RE: Chlorine Contact Tank Dynamic Control

TerryF — Wed, 05 Sep 2007 17:19:56 GMT

David,

I absolutely agree with your comment I would be an interesting design problem and it may require the whole tank configuration to be reviewed. The intent of my suggestion was to have a CCC that performs very differently at different flow rates offerring a shorter length path at low flow and a longer for some of the flow at high flow.

Regards

TerryF

RE: Chlorine Contact Tank Dynamic Control

D Shulmister — Wed, 05 Sep 2007 13:13:27 GMT

I would think that allowing short-circuiting is defeating the purpose of baffle walls in the CCC. The goal of chlorination is disinfection; short-circuiting theoretically will allow passage of pathogens to the effluent. Even though you might get a higher residual due to less detention time, the effluent may not be acceptable for reuse.

RE: Chlorine Contact Tank Dynamic Control

TerryF — Wed, 05 Sep 2007 00:13:52 GMT

Grant,

Just to start the ball rolling if your tank is baffled you could try a baffle redesign so that at low flow a greater percentage can short circuit but at high flow more is held back or has to take the long way. My original thought was if you had a maze type arrangement of baffles you put some small holes through the baffles to allow some flow to pass through relatively quickly. This would impact on your mean detention time obviously and the hole sizing will be "interesting".

Regards

TerryF

RE: Help with Hypo pump off gassing

Rob Baur — Wed, 22 Aug 2007 12:31:40 GMT

25 psi would be around 50 feet of hypo head, do you really need it set that high? One thing we did was to put a compatable low head centrifigual pump at the base of the tank to pump hypo up to the dose pump and then the excess is returned to the top of the hypo tank in a re-circulating loop. That way you always have a flooded suction and most bubbles are swept past the dose pump suction and back to the tank.