Sewage and wastewater treatment plant using anaerobic and aerobic microorganisms

A sewage and wastewater treatment plant which comprises a bioreactor having an anaerobic treatment tank for anaerobic treatment, an aerobic contacting tank and a microorganism separation tank located in between the anaerobic and aerobic tanks respectively. In the anaerobic and aerobic tanks a media is provided in a layered honeycomb type arrangement for distributing the wastewater and sewage to be treated and for adherence of microorganisms.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a sewage and wastewater treatment plant 
for treating all sorts of organic industrial wastewater, urban sewage, or 
the like, and more particularly to an economical sewage and wastewater 
treatment plant, wherein both an anaerobic treatment method for high 
concentration wastewater and an aerobic treatment method for low 
concentration wastewater are used effectively, so as to provide a simple 
and economical operation. 
2. Description of the Related Technology 
An anaerobic treatment method for high concentration wastewater generally 
has a high efficiency, even at a high loading rate, wherein high 
temperature anaerobic microorganisms (53.degree..about.57.degree. C.), 
moderate temperature anaerobic microorganisms (33.degree..about.37.degree. 
C.), and low temperature anaerobic microorganisms 
(20.degree..about.25.degree. C.) are used. It is known that, at various 
temperatures, the high temperature anaerobic microorganisms degrade 
organic materials at the fastest rate, next are the moderate temperature 
anaerobic microorganisms, and last, the low temperature anaerobic 
microorganisms. 
Considering only the respective degradation rates of organic materials, it 
seems that methods which use the high temperature anaerobic microorganisms 
would be the most effective. However, in order to treat wastewater with 
high temperature microorganisms the temperature must be raised to between 
53.degree..about.57.degree. C. and hence excessive energy is wasted 
rendering the method of no commercial value. In addition to that, the high 
temperature anaerobic microorganisms react sensitively to operating 
conditions such as temperature, pH, or the like, making them difficult to 
deal with. Therefore, methods which use high temperature anaerobic 
microorganisms have not been widely used unless a high temperature 
wastewater is generated naturally. For that reason, the most widely used 
anaerobic method is an anaerobic method which utilizes an optimal 
temperature of between 33.degree..about.37.degree. C. And, in fact the 
application range has become gradually wide. 
Anaerobic treatment has many advantages compared with aerobic treatment. 
For example, even under high concentrations of organic materials it is 
possible to maintain a high level of degradation efficiency, a processing 
waste sludge is scarcely generated, and particularly, in the case of 
anaerobic treatment of high concentration waste water, any methane gas 
(CH.sub.4) generated during the treatment process can be used as energy to 
raise the temperature of the wastewater and the treatment process is 
possible without additional energy. 
On the other hand, when moderate temperature anaerobic treatment is used to 
treat low concentration wastewater such as sewage, the amount of sludge 
generated is low and the amount of gas generated is too small to use as a 
source of replacement energy, therefore it is not economical. 
Recently, a study applying the low temperature anaerobic method to sewage 
and wastewater treatment actively proceeded. It was found that the organic 
removal rate decreases more or less but economical treatment is possible 
without additional energy. In addition to that, the organic concentration 
after anaerobic treatment is low, the amount of generating excess sludge 
is small, and as a result, the sludge treatment cost is cut down. 
Therefore, an economical treatment is made possible. Despite these 
advantages, however, the anaerobic treatment process has not been actively 
used. The reason is that the anaerobic compartment is generally separated 
from the anaerobic compartment, so the treatment plant includes an 
anaerobic compartment, an aerobic compartment, and a final sedimentation 
compartment. This means that the process is complex, the initial equipment 
investment cost is high, and it is not easy to operate the treatment plant 
compared to general sewage and wastewater treatment processes. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention has been made in an effort to solve the 
problems occurring in the prior technology. Therefore, it is an object of 
the present invention to provide a sewage and wastewater treatment plant, 
whose processing is simple, the initial equipment investment cost is low, 
and operation is easy. 
According to one aspect of the present invention, a combined anaerobic and 
aerobic process is provided wherein organic materials in the influent 
sewage and wastewater are degraded to a degree of 60.about.70% by the 
anaerobic microorganisms located in the anaerobic treatment compartment, 
and the remainder are also degraded by the aerobic microorganisms attached 
to media. 
The above treatment plant is a single tank having an interior which is 
compartmentalized into three parts, from left to right. In the front 
section of the tank there is an anaerobic treatment compartment, in the 
center section of the tank there is a microorganism separating compartment 
and therein there is a microorganisms separating apparatus installed in 
order to prevent the loss of anaerobic microorganisms caused by rising 
generating gas. And, in the rear section of the treatment plant tank, for 
aerobic treatment methods, an aerobic contacting compartment is provided 
in which the amount of excess sludge is small and sludge bulking scarcely 
occurs. 
The anaerobic compartment in the front section consists of 0.5 W of the 
entire treatment plant and under normal operating state has a 
microorganism concentration of between 20,000.about.30,000 mg/l by total 
solid substances. As seeding microorganisms, activated anaerobic 
microorganisms from the anaerobic treatment tank are used and the seeding 
amount of microorganisms is determined by the concentration of the total 
solid substances, however approximately to 50% of the volume of the 
anaerobic treatment tank. At the beginning of seeding, because of a sudden 
temperature change, it is difficult for the anaerobic microorganisms to 
adapt to the environment and the degradation of organic materials is not 
great. However, as time proceeds, the microorganisms gradually adapt to 
the environment and after about 10 days, normal degradation of organic 
materials is possible. Also, media are fed to the upper portion of the 
anaerobic treatment tank, to a height of 0.2 H, as that results in 
security of microorganisms and influent sewage and wastewater are equally 
distributed. 
In the bottom portion of the microorganisms separating tank, anaerobic 
reactions also proceed, organic materials are degraded, and the digestion 
gas generated during the degradation of organic materials is given off. 
While the digestion gas rises, surrounding microorganisms can 
simultaneously rise which can cause a loss of microorganisms. To prevent 
such a loss of microorganismsa Gas-Solid Separator (GSS) is installed in 
the microorganism separating tank located in the center of the treatment 
plant. This microorganism separating tank occupies 0.2 W of the total 
width of a bio-reactor. 
An aerobic contacting tank, which is located in the rear part of the 
bio-reactor, occupies 0.3 W and is filled with media on microorganisms in 
order to secure a plurality of fixed aerobic microorganisms. At the bottom 
of the aerobic contacting tank, a distributor is installed for providing 
oxygen to the microorganisms. Active microorganism present in sewage are 
used as seeding microorganisms and occupy 20.about.30% volume of the 
aerobic contacting tank. After initial seeding, by continuous oxygen 
supply, suspended aerobic microorganisms gradually come to adhere to the 
surface of media. 
As a result of passing through an anaerobic treatment tank, 60.about.70% of 
organic materials in influent sewage and wastewater are removed and 
passing through a rear aerobic contacting tank, 80.about.90% of the 
remaining organic materials are removed. Thus, as a result of passing 
through an entire bio-reactor, the total amount of organic materials 
removed is about 92.about.98%. 
As described above, if only an aerobic treatment process is sued to treat 
sewage and wastewater, a quantity of sludge is generated, the excess of 
which must be removed periodically. However, according to the present 
invention, the amount of sludge is so small that a high efficiency 
treatment process is possible.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a biological sewage and wastewater treatment plant 
according to the present invention. A bio-reactor includes three regions, 
a front part, a center part, and a rear part which occupy a width of 0.5 
W, 0.2 W, and 0.3 W, respectively, of the entire bio-reactor. The front 
part refers to an anaerobic treatment tank 4, the center part refers to a 
microorganism separating tank 5, and the rear part refers to an aerobic 
contacting tank 6. 
The interior of the anaerobic treatment tank 4 includes a media layer 2, 
which is located under an inlet 1, and which is fixed on supporters and 
occupies a height of 0.2 H; a space 7 is provided under the media 2 having 
a height of 0.2 H; and an anaerobic sludge bed 3 at the bottom of the 
anaerobic treatment tank, below the space 7, which occupies a height of 
0.5 H. Influent sewage and wastewater is dispersed properly within the 
entire reaction tank by the media 2 in the anaerobic microorganisms 
treatment tank 4. Media 2 assists in the degradation of the influent 
wastewater and has anaerobic microorganisms of about 1.about.2 mm 
thickness adhered on its surface. The media 2 is in a fixed state and 
consists of a plurality of crossflow-type media sheets which contact each 
other and are in a layered arrangement. 
Referring to FIG. 2, the arrangement of the media 2 is such that each media 
sheet contacts adjacent media sheets in an alternating pattern so that 
gaps between media sheets are formed. When the media 2 is complied of its 
many layers the gaps form a zigzag shape so that the gap ratio increases. 
Referring to FIG. 1, sewage and wastewater, having miscellaneous articles 
eliminated, such as waste food, vinyl and paper, prior to entering, flow 
into inlet land pass through media layer 2 which acts to distribute the 
flow of sewage and wastewater and on which anaerobic microorganisms are 
adhered. Organic materials are degraded by the anaerobic microorganism in 
the anaerobic treatment tank 4. During the degradation of organic 
materials, gas, such as methane (CH.sub.4) and carbon dioxide (CO.sub.2), 
is generated. Anaerobic degradation process means that organic materials 
are degraded to methane and carbon dioxide by microorganism, without 
oxygen (O.sub.2). This degradation process consists of a hydrolysis step, 
an organic acid producing step and a methane producing step. 
In order to prevent the anaerobic microorganisms from rising upward 
together with the gas generated during the anaerobic treatment process, a 
Gas-Solid Separator (GSS) 9 is provided in the microorganism separating 
tank 5, located in the center of the bio-reactor, wherein the rising 
microorganisms are separated. After that, the treated sewage and 
wastewater having 60.about.70% of the organic materials eliminated 
overflows into an aerobic contacting tank 6. The gas generated in this 
phase of the process is exhausted out through an exhaust outlet 10 in the 
upper portion of the Gas-Solid-Separator 9, and the microorganisms from 
the gas are precipitated. A gas diverter 8 is provided adjacent to the 
Gas-Solid Separator 9. At this time, 30% of the height of the 
Gas-Solid-Separator 9 is above the level of the liquid in order to provide 
an exhausting effect. 
In the aerobic tank 6, there is media 13 fixed on supports 12; however, 
this media 13 has a different role than the media 2 in the anaerobic 
treatment tank 4. The role of media 13 is for the adherence of aerobic 
microorganisms, and by the adherence of the microorganisms, the remaining 
organic materials are removed. Also, in the aerobic contacting tank 6, an 
air diffuser 11 is installed for providing oxygen continuously to the 
aerobic microorganisms. By the air diffuser 11, a density of optimal 
dissolved oxygen may be maintained. 
Water which has passed through both the anaerobic and aerobic treatment 
processes is separated in a precipitation part 14 installed on the upper 
portion of the aerobic contacting tank 6 and is exhausted out through an 
outlet 15. In order to minimize the overflow of microorganisms in the 
aerobic contacting tank 6, a precipitation separating stand 16 is 
installed between the aerobic contacting tank 6 and the precipitation 
part. Since the amount of anaerobic microorganisms in the anaerobic 
treatment tank 4 does not change, even with time, it is not necessary to 
remove excess sludge; however, as time passes, the activity may decrease 
as a result and thus it is necessary to remove sludge until there is 
between 5.about.10% of the volume of the anaerobic treatment tank 4 
through a sludge elimination pipe 17 once every 3.about.4 months, 
periodically. 
FIG. 3 illustrates a microorganisms separating apparatus having a 
triangular shape and has a hole on the upper part for exhausting out gas 
separated from the microorganisms smoothly. 
The invention has been described through preferred embodiments. However, 
various modifications can be made without departing from the scope of the 
invention as set forth in the following claims.