Static granular bed reactor

Details Static granular bed reactor Static granular bed reactor

2002-07-02

2004-03-23

Prince, Fred G. (Department: 1724)

Liquid purification or separation

Processes

Treatment by living organism

C210S617000, C210S618000, C210S188000, C210S258000, C210S259000

Reexamination Certificate

active

06709591

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to anaerobic treatment of low to high strength industrial and municipal wastewaters and for polishing the effluent from new and existing anaerobic systems.
BACKGROUND OF THE INVENTION
Wastewater is water used indoors including water that drains from sinks, showers, toilets, washing machines, dishwashers, and any activity that uses water in some way in homes and businesses. Wastewater is typically classified in one of three categories: high strength, medium strength, and low strength. These classifications are usually based on several factors, such as the amount of organic material in the water, measured as biochemical oxygen demand (BOD), the amount of solids “floating” in the sewage, measured as total suspended solids (TSS) or suspended solids (SS), the amount of dissolved oxygen in the wastewater, the acidity/basicity of the wastewater, and the temperature of the wastewater.
Bacterial metabolism that occurs in the absence of oxygen is called anaerobic. Anaerobic microorganisms have played a major role in traditional municipal wastewater treatment through anaerobic digestion, which has been used to degrade organic solids and stabilize waste sludges from activated sludge processes. Over the past several years, anaerobic methods have been increasingly used for industrial pretreatment to remove suspended and soluble organic matter from aqueous streams, especially in high-strength process waters.
Waste waters from chemical, pharmaceutical, pulp and paper, food, dairy, brewery and meatpacking industries are being treated successfully today with a variety of anaerobic treatment systems. Anaerobic processes are normally operated at elevated temperatures (85-95° F.) in the pH range of 6.8 to 7.4, and convert soluble organic carbon into carbon dioxide and methane, in contrast to aerobic systems which only produce carbon dioxide. The methane by-product of anaerobic systems is often used as a fuel to supply heat to the reactor.
Significant disadvantages of aerobic wastewater treatment processes over anaerobic processes are that aerobic processes require large amounts of oxygen and larger volumes for oxygen transfer, making the systems less cost effective. With high temperatures, or a combination of temperatures, anaerobic digestion can produce a high quality effluent, as in the TPAD process (Han et al., 1997
1
) or anaerobic filters operated at thermophilic and mesophilic temperatures (Harris and Dague, 1993
2
).
The use of anaerobic treatment for high-strength wastewater (generally where the chemical oxygen demand (COD) is above 3,000-4,000 mg/l or biological oxygen demand (BOD) is above 1,500 mg/l) eliminates the process limitations and problems associated with high oxygen demand and excessive biomass production that characterize traditional aerobic treatment systems. Another significant advantage of the anaerobic process for treating wastewater is that the anaerobic bacteria may release enzymes that help solubilize the organic solids in the influent, which means that both soluble and suspended BOD can be treated anaerobically.
A significant drawback of anaerobic wastewater treatment systems is that they typically require complex operation and control equipment. For instance, anaerobic systems often require mixing devices, gas or feed recirculation lines, and/or liquids/solids separators. Although necessary, these additional components often lead to operating problems.
Another disadvantage is that effluent from anaerobic processes usually requires costly post-treatment, typically at a municipal treatment facility. In addition to upkeep of the on-site treatment facilities, there is usually a charge for municipal treatment based on BOD, TSS and nutrients (such as phosphorous and nitrogen).
Anaerobic systems are well suited to the treatment of slaughterhouse wastewater. They achieve a high degree of BOD removal at a significantly lower cost than comparable aerobic systems and generate a smaller quantity of highly stabilized, and more easily dewatered, sludge. Furthermore, the methane-rich gas generated can be captured for use as a fuel.
In most countries, anaerobic ponds have been used to achieve a high reduction in BOD, oil, and grease and suspended solids concentrations from the primary-treated slaughterhouse wastewater prior, to subsequent aerobic treatment. Unfortunately, the propensity for odor generation from anaerobic ponds has threatened their continued use in many areas. Consequently, new developments in anaerobic technology during the last several years have been of considerable interest.
The testing of high-rate anaerobic systems has been one of the active areas of research concerning slaughterhouse-waste treatment during the last decade. The 1970s saw the use of low-rate anaerobic digesters to treat slaughterhouse wastewater. These processes were essentially mixed digesters with a BOD loading of between 0.2-4 kg/m
3
-day, and have proven uneconomic due to their required size. Since this time, a variety of new high-rate anaerobic technologies have been developed to replace the anaerobic pond. Typically, these are characterized as having higher BOD or COD loadings (typically 5-40 kg COD/m
3
-day) than low-rate systems or anaerobic ponds. This permits a hydraulic retention time in the order of hours, rather than days. The gas generated by the anaerobic activity is methane-rich, but in most cases H
2
S is also generated at concentrations from 0.2-0.7% from slaughterhouse wastewater and may need removal.
The NewBio reactor (U.S. Pat. No. 5,616,304) is a downflow, intermittently mixed, sludge blanket anaerobic reactor. This system consists of a covered circular tank and a water transfer/gas handling skid. The reactor includes upper and lower influent mixing blades, sand bed, fluidizing blade, slotted effluent drain, and a methane gas containment/storage area. The effluent from this system, however, requires post-treatment by filtration through a sand bed. This sand filter further has the drawback of causing clogging in the system.
An ideal biological treatment process would be easy to operate and produce a high quality effluent in a relatively small reactor volume. To achieve a high degree of organic removal at short HRTs, many anaerobic processes take advantage of anaerobic bacteria's ability to form a dense agglomeration of particles called granules. Under anaerobic conditions in the reactor, organics from the wastewater are used by different types of microorganisms as the source of energy for the biological degradation process. These organisms tend to agglomerate into flocs, referred to as sludge. Under certain circumstances, the bacteria form small roundish pellets, called granules that consist mainly of methanogenic bacteria. The sludge produces gas as a by-product of the degradation process. A small amount of the food is transformed into either free energy and water or cellular material, which is equal to the new growth of bacteria. However, a large amount of the food is transferred into gas, which consists mainly of valuable methane and carbon dioxide. The Anaerobic Sequencing Batch Reactor (ASBR), Upflow Anaerobic Sludge Blanket (UASB), Anaerobic Migrating Blanket Reactor (AMBR), and other systems produce microbial granules during normal operation.
The formation of granules has been observed in many studies. Hulshoff Pol et al. (1983
3
) found that most granules need an inert support structure to form upon, giving the organisms a building block. Others have noted that organisms adhere to other organisms forming the structure base. Usually, additional pressure is needed to force the organisms together, such as the velocity force from an upflow reactor. However, there is a selective mechanism which determines which groups will stay and which will be washed out in the process.
Granule formation is not limited to anaerobic organisms. However, most research has focused on anaerobic granules. The internal structure of the granule may vary depending on the type of substrate being degraded. Some granules contain layers created by d

Affiliated with

Also associated with

Rating

Static granular bed reactor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Static granular bed reactor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Static granular bed reactor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3251979