Liquid purification or separation – Recirculation
Reexamination Certificate
2002-05-28
2003-06-24
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Recirculation
C210S209000, C210S104000, C210S220000, C210S196000, C210S197000
Reexamination Certificate
active
06582596
ABSTRACT:
TECHNICAL FIELD
This invention relates to new methods and apparatuses for purification of water and wastewater with immobilized living cell bioreactor systems. In particular, the bioreactor systems may remove organic impurities, nitrogen, phosphorus and biodegradable solids.
BACKGROUND ART
In general, a biological wastewater treatment system usually consists of three essential components:
1. Living Biomass:
A wide variety of microorganisms have been found to remove different target pollutants. In order to maximize the efficiency of the biological treatment, it is necessary to select proper microbes depending on the types of pollutants to be treated. The acclimatization of microbial consortia for particular purposes is well known in the art. Some microbial species which have been characterized are available from recognized depositories of biological materials.
2. Biomass Handling:
A bioreactor may achieve high efficiency when it supports the living biomass to grow healthily in high density and retain them properly in the bioreactor under various adverse conditions. Biomass handling methods that are used in water and wastewater treatment may be generally classified into two general categories: suspended and immobilized biomass.
Suspended biomass systems have been widely used in activated sludge (“AS”) systems and part of rotating biological contactor (“RBC”) systems, however, the inherent limitations in these systems have driven continuous research in immobilized biomass methodology. Immobilization of living microbial cells as a means of handling biomass has gained increasing application, especially for biological nutrient removal.
Two predominant immobilization methods are a ‘biofilm’, in which the microorganisms are attached to solid surfaces, and an ‘entrapped biomass’, in which the microorganisms are held within micropores in the support material. The attached biofilm has been widely used in RBCs and trickling filters. In this method, the biomass is immobilized through adsorption and interactions between the microbial cells and the surfaces of supporting material. The immobilization of biomass using this method may be relatively weak, and the biomass periodically sloughs off the surface of the supporting material. Entrapment methods include the use of a matrix of calcium alginate gel. The major limitations of this immobilization method are that it is impractical to use in a commercial scale, as the beads are expensive and are mechanically or chemically instable. Poor mass transfer within the beads also greatly limits its application in large scale.
A porous ceramic immobilization material has been developed for large-scale applications. However, in practice, it has been found that the total suspended solids (“TSS”) and the growth of microbial cells easily clog the micropores. As the micropores became clogged, mass transfer and headloss problems occur, similar to problems which affect calcium alginate gel systems, and only a thin layer of biofilm can grow on the surface of the ceramic immobilization material.
3. Hydraulics and Mass Transfer:
A wastewater treatment system is only effective if the living biomass is provided with sufficient metabolic substrates and the waste metabolites are removed properly from the living biomass.
Obviously, the performance, flexibility and reliability of a biological wastewater treatment system are strongly dependent upon the effectiveness of the three components mentioned above. The main types of biological systems in wide use today, activated sludge (AS), rotating biological contactor (RBC) and conventional biofilters (or trickling filters) referred to above, suffer from shortcomings in one or more components mentioned above, which have been well documented in the literature.
Conventional biological wastewater treatment systems typically require a primary clarifier or sedimentation step, including the application of flocculating or coagulating chemicals, prior to biotreatment in order to mitigate the shortcomings of the prior art. This step is conventionally necessary to reduce the level of suspended solids so the biotreatment system does not become overloaded or clogged.
The biological conversion of complex or insoluble compounds containing phosphorus (P) or nitrogen (N) into simply P or N, requires a series of biochemical reactions carried out by several different microbial consortia. These organisms grow under different conditions, have substantially different growth rates, and therefore compete differently for substrates, carbon and energy sources. Thus, any biological treatment system will only be effective if it can grow different desired microbial consortia, each to a high density and in a favorable environment.
Both phosphorus and nitrogenous compounds are encountered in wastewater in two general forms—inorganic and organic forms, which together make up total phosphorus (TP) or total nitrogen (TN). Complex phosphorus and nitrogenous compounds are found in soluble and insoluble states, and usually need to be converted into simple form such as orthophosphate or ammonia before use by most microorganisms.
Facultative anaerobic processes are found to be most effective for converting complex P or N into orthophosphate or ammonia. These processes involves various hydrolyzing enzymes from acclimatized microorganisms. However, these type of microorganisms usually grow slowly, are less competitive than other microorganisms and require certain special conditions.
After biological conversion, most of the N and P are in solution, and only a portion is assimilated into the biomass. Often, the ultimate goal is to reduce the N and P compounds from the water and wastewater to specified levels to meet discharge or re-use requirements. Several biological processes for removal of the N or P compounds are well known in the art. Such conventional systems typically involve suspended growth systems or sludge wasting methods.
To biologically remove soluble P, there is need for a selection system that allows for growth and retention of the P-removal microbial consortia in the bioreactor system in a reasonable concentration. This biomass may then absorb the PO
4
—P in relatively high concentrations in its microbial cells. After reaching the maximum capacity under favorable conditions, the biomass is typically removed from the system and disposed of as waste sludge before it can release the absorbed P into the solution again. Although this treatment method may remove PO
4
—P, the P removal biomass in the process varies considerably with the wastewater characteristics and operation, and it is very difficult to control. The disposal of significant amount of wasted biomass, or sludge, is also a great burden.
The chemistry of nitrogen is more complex because N can exist in seven oxidation states. Although many species of bacteria are able to change the oxidation states of N, they usually grow slowly and are much less competitive compared to heterotrophs. In addition, the biochemical processes for conversion of N are usually kinetic limiting processes. To improve the efficiency of these biological processes, it is desirable to selectively grow the desired species efficiently and in high density in the bioreactor and it is further desirable to provide the favorable growth conditions for these microorganisms to maximize N removal efficiency.
SUMMARY OF INVENTION
The present invention comprises integrated biological processes and novel bioreactor systems. In particular, this invention comprises a series of bioreactor systems using integrated biotreatment processes for the removal of organic material or BOD, suspended solids (“SS or TSS”), N and P from water and wastewater.
In general terms, the invention comprises a method of treating water or wastewater which involves first a facultative anaerobic process to degrade solids, break down complex compounds and produce simpler forms of P and N compounds, primarily phosphate and ammonia, as well as volatile fatty acids (“VFA's”). The VFA's are then contacted with a P-removal microbial consortia which uptakes and
Aquasol Envirotech Ltd.
Barry Chester T.
Bennett Jones LLP
LandOfFree
Bioreactor systems for biological nutrient removal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bioreactor systems for biological nutrient removal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bioreactor systems for biological nutrient removal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3148612