Ammonia removal concept for review and comment

[alphamaleomega]

I have a 50,000 gpd wastewater stream with parameters as follows:

15 degrees C
100 ppm ammonia,
PH=7.2,
TSS=nil,
BOD5=200,
COD 300 ,
flow rate,
nitrate=0,
nitrite=0.

Need to get rid of the ammonia, and discharge at 20 ppm ammonia or less.

Plan on generating chlorine on-site using a membrane and electrode system, then using the NAOH produced on the cathode to condition one half of the flow to PH to 10.5 + and then air strip the ammonia. May generate chlorine off-site near the ocean and be able to produce it without generating a waste stream and having to haul salt.

The other half of the flow would be treated with chlorine to the breakpoint eliminating all of the ammonia and chloramines.

The flow would be then be re-combined and treated with UV to De-chlorinate, prior to discharge.

Have investigated cost of nitrification/denitrification using biological reactors and favor the chemical method for reliability and quick start-up due to intermittent flows. I realize operation costs are higher.

Any comments appreciated.

 

[FiltrationEngineer]

What kind of wastewater? From what process?

 

[bimr]

Obviously, you have not checked into the price of generating chlorine onsite or you would not consider doing so. Only one word fully describes the cost of such chlorine generating systems and that word is outrageous.

Secondly, the downfall of the air stripping process is that the salts that are typically present in the water will cause extensive and excessive scaling at the pH of 10.5. You have not presented a water analysis, but you should be aware of that scaling possibility.

Finally, you will still need to treat the wastewater to remove the BOD. How are you proposing to accomplish the BOD removal?

 

[alphamaleomega]

Wastewater stream is a sludge dewatering filtrate.

Cost of chlorine is high but more favorable than buying chemicals, and over time will save money. Looking at several different chlorine generators.

Scaling can be controlled by washing periodiclly with HCL solution

 

[bimr]

I am sure everyone will interested in volunteering to do the acid wash. Sounds like fun.

Have you ever run across anyone that is doing this ammonia air stripping? My experience has been that it is an idea that many propose, but once the details become evident, very few are willing to pursue.

Have you also thought about an air permit? Ammonia is considered to be an air toxic in some quarters. The amount would be about 3-8 tons per year depending on what you are doing.

There are two aspects to the cost. The capital cost of chlorine generation is outrageous. Secondly, the stoichemetric requirements for chlorine will cause the operating cost to be very high.

The initial impression is that ammonia stripping is a bad idea, compounded by the second bad idea, onsite chlorine production.

Fail to understand why you just don't aerate this filtrate and put it back into the front of the wastewater treatment plant. Surely this must be a small stream in comparison to the wastewater treatment plant.

 

[alphamaleomega]

This wastewater stream is intermitent, and we are in a very cold climate. The waste characteristics can change rapidly. We may use aerobic treatment followed by anerobic treatment but these plants require full time operation, and an upset causes us great problems, as we have no place to store effluent.

Still evaluating the options, that is why I am posting here.

Thank you all very much for your comments.

Alpha

 

[jmj5152]

The ammonia level is not too high for treatment via unconventional means.
Have you considered electrochemical (anodic) oxidation? Probably cost you less in electricity consumption than the chlor-alkali route you are considering.

Air stripping is generally recommended for higher concentration.
Off the beaten path approach would be to pull it off on an ion exchange resin. If you control regeneration volumes, you can create a concentrated ammonium sulfate or ammonium chloride salt solution that can be sold to the fertilizer guys.

 

[orenda1168]

Alphamaleomega:

Contact RCP International,LLC at 541-557-4108, or 800-322-1648, or Fax: 541-994-3228, or water@infoecp.com if you would be interested in their electrolytic-catalytic (ECP) treatment system that will efficiently and economically control ammonia, BOD and COD concentrations to discharge requirements, without the concern of system reliability in weather extremes,influent quality variations or the issue of chlorination/dechlorination.

Orenda

 

[jmj5152]

Orenda 1168:

As I understand, the ECP unit also uses lanthanum chloride, and primary oxidation is achieved via the same mechanism as electrolytic splitting of NaCl. I have a hard time understanding how the microbes survive with chlorine around? Or, how they survive the oxidation potential at the anode of an EC cell?

 

[orenda1168]

Jmj5152:

Lanthanum chloride is applied downstream of the ECP and ONLY in those cases requiring residual ortho-phosphate removal post-ECP to meet discharge criteria. Depending on the trace element components present in the water to be treated, some or most phosphate can be precipitated out, e.g. as calcium phosphate, for filtration removal though this invaribly leaves a residual requiring further reduction.

The ECP system generates substantial quantities of oxidizing species, predominately OH and O, with others in lesser amounts. With the presence of chlorides in the water, some hypochlorus acid is formed, with produced chlorine mostly gassed off. Usually (with the obvious exception of sea water or a high chloride brine commonly encountered in produced water from petroleum production activities) insufficient chlorine is produced to significantly effect microbes of any description because of the rapid gas-off effect. However, all microbes, fungi and other similar life forms ARE rapidly oxidized(killed) as they pass through the electrode chamber(s), generally to the extent of 98%-99.9% of the original count.

As a point of interest, USDA in Oregon is in the throws of evaluating the ECP for kill-off of a wide variety of plant pathogens, such as Sudden Oak Death and others that plague the horticultural market world-wide. The initial data shows what was expected....complete kill of the pathogens evaluated to-date. The balance of the work will be completed over the next two months or so, with the data then available for USDA's peer review and publication.

Beyond this attribute of the ECP system which is in many cases considered to be an ancillary benefit, the ECP is principally applied to 1) oxidize water-born organics to below discharge limits, and 2) oxidize trace metal elements that will form insoluble oxides/hydroxides (mostly) and be removable by filtration. By virtue of the oxidizing mechanisms within the ECP system, such materials as ammonia and nitrites are oxidized to nitrates, and BOD/COD concentrations are usually reducible to or below discharge limits.

Please contact me at orendatech@earthlink.net if you would like to discuss this technology further.

Regards,

Orenda

 

[cub3bead]

If I recall corrrectly, air stripping will require a pH of 11.0+ to acheive reasonable results. However, that will only make the scaling issue worse in the stripping tower. I hope you don't have a lot of Ca, Mg, or carbonate alkalinity in the water because you will have lots of joy if you do.

 

[jmj5152]

Orenda: So how is it different from an ordinary electrochemical cell which also oxidizes at the anode with the same species? Ammonia and nitrite oxidation to nitrates at the anode has been done for a long time, but is typically not efficient in flow through systems such as the one described in this string.