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Ammonia is widely used in the Chemical Industry as a cleaning and bleaching agent in the production of fertilizers, plastics, and explosives just to name a few. As a result, large quantities of wastewater containing ammonia are produced and many industries now have to treat the wastewater to remove the ammonia so that it is not discharged back into the environment. The following are the various methods followed for the removal of ammonia.
This section provides details on the latest developments and efforts in the removal of ammonia from wastewater.
We have discussed the following:
- Current Wastewater Treatment Process – Ammonia Removal
- New Technologies in the Removal of Ammonia from Waste Water
- Successful Ammonia Removal from Wastewater Using Liqui-Cel® Membrane
- Ammonium Removal from Concentrated Waste Streams with the Anaerobic Ammonium Oxidation (Anammox) Process in Different Reactor Configurations
- How CASTion Helps Remove Ammonia
- Ammonia removal in Wastewater Treatment Applications with BIOBUG® NB from BIO-SYSTEMS International
- Ringlace Fixed-Film Media
Current Wastewater Treatment Process – Ammonia Removal
Ammonia is usually separated from wastewater by the ion exchange process. In conventional sewage plants ammonium is converted to nitrogen by executing two oxidation steps, in which nitrogen is first converted to nitrite and subsequently to nitrate (nitrification), whereupon the generated nitrates are reduced in a two-step reduction process first to nitrite and subsequently to molecular nitrogen (denitrification). Depending on the process method employed nitrification and denitrification may be performed in the same reactor one after the other, or they may be carried out in different reactors.
New Technologies in the Removal of Ammonia from Waste Water
Successful Ammonia Removal from Wastewater Using Liqui-Cel® Membrane
There are many conventional ways to remove ammonia from water but most of them produce a secondary waste stream that can cause a whole list of other problems. Membrane Contactors offer a superior solution for stripping Ammonia because they provide a large surface area that facilitates fast separation of the ammonia from the wastewater. The extraction process uses Liqui-Cel® Membrane Contactors.
- The process is durable and reliable.
- They offer a great alternative by extracting ammonium salt during the treatment, which has some commercial value.
- It is cost effective.
For ammonia removal, wastewater will flow through the shell side (outside of the hollow fibers), while an acid solution will flow countercurrent through the lumen side (inside of the hollow fibers). The composition of the ammonium salt at the end of the process will depend on the acid used in the stripping process. For example, a sulfuric acid extractant stream will convert ammonia into ammonium sulfate. Ammonium sulfate is widely used as a fertilizer and it could be sold with commercial value.1
Ammonium Removal from Concentrated Waste Streams with the Anaerobic Ammonium Oxidation (Anammox) Process in Different Reactor Configurations
Many concentrated wastewater streams produced in food and agro-industry are treated using sludge digestion. The effluent from sludge digestors frequently contains ammonium in high concentrations (up to 2 kg m−3). This ammonium-rich effluent is usually treated by a normal wastewater treatment plant (WWTP). When ammonium removal from this concentrated stream is considered, steam stripping or a combination of two biological processes, aerobic nitrification and anoxic denitrification, are the (costly) options. Recently, a novel process was discovered in which ammonium is converted to dinitrogen gas under anoxic conditions with nitrite as the electron acceptor. It has been named Anammox (anaerobic ammonium oxidation). The aim of this study was to demonstrate the feasibility of ammonium removal from sludge digestion effluents with the Anammox process. Using a synthetic wastewater, it was shown that a fixed-bed reactor and a fluidised-bed reactor were suitable reactor configurations. The effects of sludge digestion effluent on the Anammox process were investigated; during 150 days, 82% ammonium removal efficiency and 99% nitrite removal efficiency was achieved in a fluidised-bed reactor inoculated with Anammox sludge and fed with sludge digestion effluent from a domestic WWTP. The maximum nitrogen conversion capacity was 0.7 kg NH+4-N m−3reactor day−1 and 1.5 kg total N m−3reactor day−1.2
How CASTion Helps Remove Ammonia
Typically, 40-50% of the total nitrogen in a municipal wastewater treatment plant is found as ammonia in the centrate or filtrate streams. During ammonia removal, wastewater progresses through the RCAST Ammonia Removal and Recovery Process. This is a compact, high efficiency system, that combines flash vacuum distillation with ion exchange to remove 90% of the ammonia in these streams at a much lower cost than traditional biological removal systems. This results in the recovery of ammonia for reuse as ammonium sulfate, a common fertilizer. After undergoing successful ammonia removal, wastewater is then recycled back to the main municipal plant or used as process water in an industrial process.3
Ammonia Removal Process
To begin the Ammonia Removal Process, the ammonia in industrial wastewater is conditioned so that neither suspended solids nor precipitates can reach the ammonia removal systems. If the ammonia concentration is high, vacuum stripping using RCAST ammonia removal systems is used to capture the ammonia that would readily volatilize (about 80%). Influent (with 300 ppm ammonia-nitrogen or less) is then input to an industrial grade ion exchange resin which selectively adsorbs the ammonia. The adsorption columns are regenerated using either a brine or sulfuric acid. The regeneration solution is used repeatedly, where the ammonia concentration builds up to several thousand ppm. The spent ammonia-laden regeneration solution is stripped of ammonia to produce a commercial-grade (about 40%) solution of ammonium sulfate.
- Different from biological treatment, this process physically converts ammonia in wastewater to nitrogen and steam using the stripper and the catalytic converter.
- Without chemical (i.e. methanol) injection
- Uses of a self-compressing system (Compress the generated steam to use the heat as a heat source) permits steam saving in ammonia distillation column.
- Conversion of ammonia into non-toxic, odorless nitrogen and steam
BIOBUG® NB is a bacterial powdered Nitrification product offered by BIO-SYSTEMS International Corporation for Ammonia Removal/Reduction. BIOBUG® NB contains a special blend of microorganisms to provide a consistent seed of both types of nitrifiers for ammonia conversion. The nitrifying bacteria are composed of two groups; Nitrosomonas spp. and Nitrobacter spp. The Nitrosomonas spp. convert ammonia to nitrite and the Nitrobacter spp. convert the nitrite to nitrate. Variations in pH, temperature, and the concentrations of organic material influence the activity and growth rates of nitrifying bacteria. As a result the nitrifying population of many wastewater facilities is frequently destroyed or washed out of the system because of its inability to competitively reproduce at a sufficient rate.
BIOBUG® NB, by utilizing selected strains of both Nitrosomonas spp. and Nitrobacter spp has been possible to adapt the bacterial cultures to function over a wider range of pH values than those normally encountered in the nitrifying population. Similar adaptation and selection techniques have been employed to increase the toxic threshold limiting concentrations of ammonia, nitrate and nitrite which may inhibit the growth of these extremely sensitive microorganisms. BIOBUG® NB has demonstrated the ability to remove ammonia, nitrite and nitrate.4
Ringlace Fixed-Film Media
Ringlace material was developed in Japan in the 1980's and consists of a rope like material of high surface area and a chemical composition conducive to bacterial attachment and growth. Biomass densities on the ringlace material approximate that found on trickling filter media or other high rate attached growth systems.
Ringlace systems are widely used in Japan and have recently been used extensively in the eastern US to upgrade municipal activated sludge plants to provide nitrification. Ringlace is currently being installed or considered for use by RBD for additional wastewater treatment needs in Colorado including: BOD removal and nitrification upgrade for activated sludge systems: BOD treatment capacity upgrade for aerated lagoons: and pretreatment for brewery wastewater.5
Carbtrol offers a line of ammonia removal systems for removal of ammonia from wastewater using selective ion exchange resin. The media removes only the ammonia, non-polluting constituents pass to the sewer. When the resin becomes saturated, it may be regenerated onsite or sent offsite for processing. Complete systems are available to handle flow rates up to 200 GPM. Ammonia can be reduced to low ppb levels.
In addition, Carbtrol offers ammonia removal systems for removal of ammonia vapor from air streams using phosphoric acid impregnated carbon. Systems are available to handle flow rates from up to 20,000 CFM. An extraction fan can also be provided to pull the air stream through the carbon bed.
2Marc Strous, Eric Van Gerven, Ping Zheng, J. Gijs Kuenen and Mike S.M. Jetten, 1997. Ammonium removal from concentrated waste streams with the anaerobic ammonium oxidation (Anammox) process in different reactor configurations. Water Research, 31 (1955-1962).
5Michael Richard, Presented at the Rocky Mountain American Waterworks Association.