Discharge from a sodium hypochlorite facility

[CivEnvEng98]

Hello all,

Looking for insight into what technologies are being used for treating the waste streem of a sodium hypochlorite facility.

Here is the characterization:
21,000 gpd
14,100 lbs/day of Sodium Chloride
233 lbs/day of Sodium Chlorate
341 lbs/day of Sodium Sulfate
445 lbs/day of Calcium Chloride
0.12 lbs/day of Silicone Dioxide

The receiving WWTF is only at 2.4 MGD +/- so this waste stream would have a significant and negative biological impact and we must find a way to lower sodium and chloride levels.

Dilution you say? Try 11 + MGD of local well water to dilute to the Utility's request of 250 mg/L of chlorides at the point of entry to the sewer collection system. No can do.

We belive the only solution is to 1) incinerate the waste stream or 2) create a filter cake for ultimate disposal at a local landfill or one that accepts haz materails, if needed.

I know of zero discharge facilities, but haven't been told yet whether or not this facility will go that route.

We have a few options in mind, but would like to see what ideas you all can come up with.

Any help would be appreciated!

 

[bimr]

Why haven't you thought of using an evaporator? It will be much less expensive than an incinerator and you will be able to recover the water as well.

http://es.epa.gov/vendors/preview/2485.html

If you are located in an arid climate, you can use solar evaporation.

By the way, most WWTP plants do not have strict limits on chlorides at 250 mg/l.

 

[CivEnvEng98]

bimr,

Yes, we thought of evaporators. I called an evaporator vender yesterday PM (after my original post) and that vendor said he could only reduce the waste volume by 75 %, based on the concentrations of the constituents in my waste stream. At some point the corrosivity of the waste stream would be prohibitive to reduce any further. So I have a reduced volume (which I still need to treat) but now a product too corrosive for conventional materials. Downstream of the evaporator all the equipment would have to be FRP or equal.

I agree 100% with your statement regarding the 250 mg/L of chlorides, but if you do a mass balance based upon direct discharge and the volume of effluent the wastewater plant puts out the CL concentrations would be 529 mg/L and the Na would be 338 mg/L. This WWTF sends reuse to golf courses and those concentrations would kill the grass.

I have read about adding perlite to the stream followed by a belt filter press which creates a filter cake that is OK for a landfill….what are your thoughts?

 

[bimr]

Suggest you call the link listed above for an evaporator. All evaporator applications basically involve the same brine salts (for example, sodium chloride) so the vendor comment regarding "corrosivity of the waste stream' does not make any sense. If you want to reduce the liquid volume, you have not other choice than to evaporate.

The evaporation process consists of 2 stages. The first stage is a brine concentrator, which will give you a concentrated brine stream. The second stage is a crystalizer, which will remove the rest of the water and provides a dry product.

Not sure that you will find this solution to be economical, but if you want to get rid of the salts, it is the only technical solution.

Regarding the chloride concentration, I am not disagreeing with you, I was just pointing out that it is highly unusual to have a discharge limitation on salts.

You may also find it economical to discharge the maximum permitted mass volume of salts to the wastewater system and then evaporate any mass volume that is above that permitted limit.

Conversely, you may evaluate moving the facility to a location with a more amenable wastewater treatment system.

 

[CivEnvEng98]

bimr,

Thanks for your excellent input (as always).

I've already been in touch with Niro Inc. regarding crystallizers.

We've also been in touch with the Utility regarding discharging a portion of the stream up to a max limit...much like a TMDL.

Thanks again.

 

[bimr]

RCC basically invented the market for waste evaporators and has the largest number of units online. That is the reason for talking to them. Here is a typical project:

http://goliath.ecnext.com/coms2/gi_0199-1797897/EDI-meets-challenge-of-evaporator.html

To my knowledge, Niro is not even in this business.

 

[JLA4ChE]

Have you looked at agitated thin film evaporators? They can typically use a vacuum, indirect heat, and an agitator to achieve the evaporation. Unlike tubular evaporators they can take a slurry and discharge a powered. Just google “agitated thin film evaporators” and look for someone who has pilot capabilities to test your stream.