Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2000-07-03
2003-07-08
Prince, Fred (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S616000, C210S631000, C210S903000
Reexamination Certificate
active
06589425
ABSTRACT:
BRIEF SUMMARY OF THE INVENTION
The invention concerns a process for treating industrial waste waters highly loaded with ammonium. In accordance with the invention “ammonium” is understood as meaning both ammonium compounds as well as ammonia
BACKGROUND OF THE INVENTION
Waste water loaded with ammonium, including highly loaded industrial waste water, can be purified in different ways. In the case of physical purification, the pH value is increased by the addition of lye, whereupon ammonia is removed by stripping with steam or with a gas and recovered by condensation. The profit from the recovered ammonia is very small in comparison with the high investment costs, and, in addition, waste waters can only be purified if they contain less than 100 mg NH
4
-nitrogen (NH
4
—N) per liter in this way.
A chemical process for removal is based on the precipitation of magnesium ammonium phosphate. In this case magnesium salts and phosphates are added to the waste water, magnesium ammonium phosphate precipitates out at a specific pH value. The magnesium ammonium phosphate can be reprocessed by heating, producing magnesium hydrogen phosphate and ammonia, which can be removed by stripping. The magnesium hydrogen phosphate then can be added to the waste water again as a precipitation agent. However, this process is very cost-intensive.
A further, more economical, biological process includes treating of the waste water with nitrifying microorganisms (nitric bacteria), the nitric bacteria being colonized on a solid carrier bed. The waste water is aerated, the nitric bacteria oxidizes the ammonium nitrogen to nitrite (Nitrosomonas) or to nitrate (Nitrobacter).
Formerly the solid carrier bed for this process in general contained lava, while more recently, in general, plastic bars, balls, or fibers have been used. These materials create a colonization surface for the nitric bacteria.
A three-stage fluidized bed reactor, in which the biomass is colonized on a carrier substance (basalt), is presented in article No 20 by J. Mihopulos, “Cost-reducing Strategies for Water Treatment Plants: Separate Turbid Water Treatment” in the book “Stickstoffrüickbelastung—Stand der Technik 1996/1997—Zukünftige Entwicklungen” by J. St. Kollbach and M. Grömping, T K-Verlag Karl Thomé-Kozmiensky. This substance is held In suspension with recirculation. However, the carrier substance is fairly large-grained. In addition, its specific surface is below 10 m
2
/g. If the aeration stops, the carrier substance is precipitated, thus leading to blockage and death of the biofilm.
A process for nitrogen removal in water treatment plants with a biological treatment stage, partial flows of the sludge treatment highly loaded with ammonium being used for growing nitric bacteria, is known from “Korrespondenz Abwasser”, 12, 1994, p. 2261-2268. The active biomass obtained is used for promoting the nitrification in the subsequent purification stages. The use of nitric bacteria In the presence of aluminum and iron hydroxides is supposed to lead to a significant elimination of nitrogen in the treated waste water during the nitrification phase. Also, a considerable amount (67%) of the nitrogen loading already should be removed from the partial flows used for growing the nitric bacteria. In addition, the metal hydroxides loaded with nitric bacteria are removed with the sludge and can lead to environmental pollution as they easily release the corresponding trivalent cations.
DETAILED DESCRIPTION OF THE INVENTION
The invention is based on the problem of treating industrial waste waters highly loaded with ammonium with the use of carrier substances, which make proper operation of the nitric bacteria possible with low investment and operating costs and largely prevent release of multivalent cations from the separated sludge.
Thus, one object of the invention concerns a process for treating industrial waste water highly loaded with ammonium in the waste water field by treating the waste waters with nitrifying microorganisms (nitric bacteria) In the presence of a suspended carrier substance, which is characterized by the fact that a silicate carrier substance with a specific surface area of >20 preferably >50 m
2
g, is added to the waste waters and suspended therein, and the nitrifying waste waters are optionally subjected to a denitrification with denitrifying microorganism (denitrifying bacteria).
The specific surface area is determined according to the BET method (one-point method with nitrogen according to DIN 66 131).
Preferably a natural silicate carrier substance with a particle size wherein 95% by weight <150 &mgr;m is used. In this way it is assured that the carrier substance also remains in suspension without expensive stirring devices. Natural silicate carrier substances, as opposed to synthetic carrier substances, are less Inclined to release hazardous substances as they have been subjected to a natural leaching process over geological time. Thus they are more environmentally compatible than synthetic silicate carrier substances.
The silicate carrier substance in accordance with the invention offers a high colonization surface for the nitric bacteria. The high colonization surface makes it possible to treat waste water with high NH
4
concentrations, which can no longer be treated according to the known biological process. Preferably industrial waste water with an NH
4
—N content of about 200 to 2000 mg/liter, in particular with about 400 to 1600 mg/liter, is used.
The silicate carrier substance in general is used in amounts of about 5 to 50 g/liter. Also it Is Important that the specific weight of the carder substances is over 1.5 g/cm
3
, so that the carrier substance does not float during aeration.
Preferably the silicate carrier substance has a surface pH value of about 6-9. This is determined by stirring a 10% by weight suspension of the silicate carrier substance in water for 15 minutes. The pH value is determined in the filtered solution by means of a glass electrode. Surprisingly it was found that a silicate carrier substance with a surface pH value outside of the indicated range has a low colonization density for the nitric bacteria, and that the colonization density also is not increased significantly, if a pH value within the indicated range is set by the addition of acid or lye in the suspension of the silicate carrier substance.
Preferably the silicate carrier substance has a cation exchange capacity (IEC) of around 40 to 100 meq./100 g, in particular 50 to 80 meq/100 g. The cation exchange capacity is determined as follows:
The dried silicate carrier substance is reacted with a large excess of aqueous NH
4
Cl solution. After a standing time of 16 hours at room temperature it is filtered, the filter cake is washed, dried, and ground, and the NH
4
content in the carrier substance is determined according to the Kjeldahl method.
In addition, the silicate carrier substance preferably also is hydrophilic, that is, it should have a swelling volume of around 5 to 80 ml/2 g, preferably of around 10 to 20 ml/2 g. The swelling volume is determined as follows:
A calibrated 100 ml measuring cylinder is filled with 100 ml of distilled water. 2.0 g of the substance to be measured are added slowly to the water surface in portions of 0.1 to 0.2 g. After the material sinks, the next portion is added.
After the end of the addition one waits for one hour and then reads the volume of the swollen substance in ml/2 g.
Because of the relatively small particle size and the swelling capacity it is assured that the carrier substance remains suspended homogeneously. If the mixture of waste water and silicate carrier substance tends to foam, antifoaming agent can be added.
Preferably clay minerals, in particular smectitic clay minerals, such as bentonite, vermiculite, chlorite, beidellite, hectorite, nontronite, and illite, are used as the silicate carrier substances. Bentonite (main mineral montmorillonite), which in addition to its function as a colonization surface also adsorbs ammonia and NH
4
+(in the latter case on the basis of
Högl Christian Eric
Högl Cindy Diana
Högl Maximilian
Högl Undine Gabriele
Cox Scott R.
Högl Christian Eric
Högl Cindy Diana
Högl Undine Gabriele
Prince Fred
LandOfFree
Method for treating process waste waters highly charged with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for treating process waste waters highly charged with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for treating process waste waters highly charged with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3109384