Hi Rohana Carolyne Putri ,

For the removal of Ammonia you can follow biological methods like Anammox or use any specific microbes (bactaria/algae). Also, you can try Struvite precipitation i.e. done by adding Mg or Ca salts with phosphate salts. The system containing high COD and BOD, the Struvite precipitation works. But, if the TDS of your wastewater high, the efficiency of both biological and Chemical ammonia removal will be affected.

You can refer the following articles,

DOI: 10.1039/C5RA20492E

DOI: 10.1080/09593330.2017.1408689

Regards,

Maharaja.P

Since you have high BOD (and COD), through aerobic digestion (high rate aeration) you can convert much of the ammoniacal-N and BOD into microbial biomass (sludge) with the remainder of the BOD converted into CO2 through microbial respiration. Depending on the initial wastewater pH, there will be ammoniacal-N loss through NH3 volatilisation and aeration can accentuate such loss.

Conversion of ammoniacal-N into nitrate by aeration (i.e. nirification) is not possible at high BOD levels.

However, once you have reduced BOD levels to low levels (when heterotrophic microbial activity begin to slow down, e.g. at Food:Microbes (F:M) ratio of

Rohana Carolyne Putri : even if you do not mention the amount of treated wastewater (hourly, daily) and you have high COD, BOD and ammonium nitrogen I believe that the best solution for your problem is biological treatment, Don´t forget remember that every chemical addition has negative influence upon final quality of treated wastewater.

Best regards

Vit

Breakpoint chlorination.

Excuse me @Rohana Carolyne Putri, does the wastewater contain domestic wastes? For which it contains BOD? Also please specify BOD5 and COD recorded by laboratory. To tell you the truth to remove ammonia, the most economical way is Biological Treatment through Extended Aeration where Cell Residence Time is (20-30 days). I also agree with my respected colleague @ Henrik Rasmus Andersen regarding Break Point Chlorination if it is the most economical.

That you describe sounds like water that should be treated by a nitrifying bioreactor. Nitrification can be more difficult in industry wastewater than municipal as the wastewater might occur periodically or contain inhibitory chemicals for nitrifyers. Lack of other nutrients like phosphor and trace metals can also be a problem.

For this reason breakpoint chlorination was previously common and obviously it still works, but chlorination of water with high COD and BOD as you describe is problematic.

Modern industry wastewater treatment would in most cases be a biofilm system solution like MBBR, which is resistant to intermittent loading and tend to be more robust to inhibitory chemicals.

I agree with you dear @Henrik Rasmus Andersen.

Whilst conventional aerobic digestion is performed in ponds or reactors at high rate or extended aeration (e.g. Activated Sludge) which could serve the purpose, other bioreactors such as TF (trickling filters) or MBBR (Moving Bed Bio Reactors) can also be designed to accommodate high BOD and high ammoniacal-N levels in effluent. In principle, such bio-film based reactors complete aerobic digestion initially (i.e. bacterial assimilation of C, N and P and respiration) but go onto completing other processes such as nitrification and denitrification effectively.

As Henrik pointed out, bio-film systems (unlike conventional activated sludge unless under extended aeration) can cope with shock loading effectively.

If you have a hi Ammonia concentration, Stripping could be also an alternative and a way to recover ammonia for fertilizer (for example). Raise the pH (NaOH, KOH etc.) , inject stream or raise temperature and It favorize ammonium to escape in the form of ammonia (gaseous). You can harvest gaseous ammonia with acid (sulfuric=ammonium sulfate...). There are many commercial process that actually exist with this approach.

For low concentration and no need to recovery, yes the biological way (nit/denit) is the usual approach.

Yann

Ammonia stripping may suit wastewater containing high ammoniacal-N or urea-N wastes with low BOD levels from some specific industrial sites.

In the case in our current discussion we have two key contaminants such as high BOD and high ammoniacal-N to treat. Once ammonia is stripped using a chemical method, we need to find a method to strip BOD effectively.

Ammonia stripped wastewater with high BOD levels may be resistant to biological treatment because of high C:N ratio (high C and low N). With the use of strong alkali such as KOH and NaOH, any remaining organic-N also would have mineralised into ammonical-N which would have been stripped by NH3 volatilisation from elevated pH (organic-N + KOH → ammoniacal-N (NH3 + NH4-N) (high pH & high temperature) → NH3↑) leaving wastewater with very low N levels.

In biological aerobic digestion methods (whether it is activated sludge or biofilms), assimilating bacteria will require sufficient ammoniacal-N to strip BOD into bacterial biomass and CO2.

If we deploy chemical stripping method as a primary method to strip ammonia, we need to propose a method to remove remaining high BOD.

Chemical method of stripping NH3 may be warranted as a pre-treatment prior to biological method, only if the wastewater has very high 'toxic' levels of ammoniacal-N which are not conducive to biological methods.

Hi,

I completely agree with Yann Le Bihan and Selva Selvarajah.

In wastewaters with high concentration of ammonia (>350-500 mg N/L), ammonia stripping is the only effective way of removing ammonia as NH3. Stripping can be done by air stripping method and by steam stripping method. In both the methods, the pH of the wastewater needs to be raised by adding caustic or lime to pH >9.5. Though lime is less preferred than caustic, raising pH ensures all ammoniacal nitrogen in the wastewater to be present in ammonia (NH3) form which is the strippable form of ammoniacal nitrogen. Steam stripping is more effective than air stripping and is preferred where steam is readily available. Air stripping is also effective, but needs more higher pH than steam stripping. Stripping of ammonia can be carried out irrespective of whether the wastewater contains high concentration of organics or not. The stripped ammonia from the stripper can be scrubbed in sulphuric acid to get ammonium sulphate which is a sell-able product. Ammonium sulphate has many commercial uses.

The second method of removing ammonia chemically is the precipitation method (struvite). Struvite precipitate forms if ammonia in the wastewater is reacted stoichiometrically with magnesium and phosphorous salts. Through struvite precipitation is easy and like ammonium sulphate, struvite also has a commercial use, the precipitation reaction takes longer time to complete than stripping and unlike stripping, this method demands high chemical consumption. The uneacted phosphate and magnesium also needs further downstream treatment.

Both the methods of ammonia removal does not significantly reduce organics unless the organic fraction in the wastewater is contributed by volatile organics (VOCs). Hence, whether or not a stripper or chemical precipitation method is applied as a pre-treatment method for removing ammonia, downstream biological treatment is essential. In both the treatment options, some residual ammonia would be left which must be removed biologically.

Biological nitrogen removal is a complex and sensitive process, yet, the only most cost effective process available till date for removal of ammoniacal nitrogen of concentrations > 350 mg N/L. Nitrogen removal through biological method needs two to three stage biological process for sequentially removing organics in the first place and followed by nitrogen. Nitrogen removal is conventionally carried out by nitrification and denitrification process. However, recently aerobic processes have been found to simultaneously nitrify and denitrify ammoniacal nitrogen to N2 via SND process. ANAMMOX process is yet another approach for converting ammonia to nitrogen in single step if the wastewater is in low organics and high in ammonia.

Selva Selvarajah, You are right, remove COD or BOD first with biological conventionnal process. It takes nitrogen that microorganisms need for assimilation (protein, enzyme and ...) the remain nitrogen could be remove by nit-denit (with additionnal carbone if need) or by a chemical approach.

Yann

Good discussions Yann and Rima.

There has been considerable focus on nitrification and denitrification to strip N in wastewater. The reality however, is unless BOD is brought down to a level that provides less competition between the heterotrophs (i.e. ammonium assimilators which convert ammoniacal-N to microbial protein) and autotrophs (nitrifiers which convert ammoniacal-N to nitrate-N) nitrification rate could be very slow.

By the time BOD is reduced to conducive levels for nitrification (Food:Microbes < 0.25), considerable amount of ammoniacal-N can be transformed into microbial protein (microbial biomass or sludge) by aeration. Aerobic digestion which is primarily promoted as a process to remove BOD can remove substantial amount of BOD by microbial biomass and microbial respiration (CO2).

As I stated before, modern biofilm technologies such as MBBRs provide ideal conditions for high microbial assimilation of ammoniacal-N and SND (simultaneous nitrification and denitrification).