JPH03123698A - Treatment of excretion sewage - Google Patents

Abstract

PURPOSE:To improve a conventional system in the aspect of maintenance and control properties, the stability of the quality of discharge water, an installation area and construction cost by using the removal of nitrogen due to an RO membrane in combination with a biological nitrifying and denitrifying method. CONSTITUTION:A flocculant 2 is added to excretion 1 to form strong and large flocs which are, in turn, separated by a fine mesh screen 3. Since the fiber component contained in the excretion 1 coexists in the separated flocculated sludge 4, the sludge 4 is excellent in dehydration properties and can be easily dehydrated up to moisture of about 60% by a screw press. The excretion 5 separated by the screen is supplied to a residue removing excretion storage tank 6 in such a state that the greater part of SS and colloidal matter is flocculated and removed to be stored therein. Pref, nitrifing bacteria and denitrifying bacteria are allowed to be present in the storage tank 6 and air is supplied to the tank 6 from an air diffuser 7 and the period when the screen separated excretion 5 is stored in the storage tank is utilized to remove the greater part of BOD and a nitrogen component.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an innovative treatment process for human waste, such as human waste and septic tank sludge.

<Conventional technology> Currently, the human waste wastewater treatment process, which is recognized as the most advanced and whose track record is increasing, is called the membrane separation method.
This is the process shown in the figure.

In this process, human waste 21 is removed from human waste 23 using a fine mesh screen 22, and the obtained human waste 24 is stored in a human waste storage tank 25, and then supplied to a biological nitrification and denitrification process 26 without dilution. After treatment, the activated sludge is separated into solid and liquid using an ultrafiltration (UF) membrane 27, and consists of a return sludge 28 portion that is returned to the biological nitrification and denitrification process, and an excess sludge 29 that is processed by a sludge dehydrator. Solid content and membrane permeated water 30 are obtained. After adding an inorganic flocculant 31 such as FeC1z+Altun to the UF membrane permeated water 30, the generated flocs are transferred to the second UF, membrane 32.
The sludge is separated into flocculated sludge 33 and membrane-permeated water 34, and the membrane-permeated water 34 is further adsorbed with granular activated carbon 35 to remove COD and chromaticity to obtain effluent water 36.

However, when the above-mentioned conventional state-of-the-art technology is evaluated with a dispassionate eye, the following serious problems exist, and it cannot be said to be an ideal process at all.

That is, ■ The core process of the treatment process is a non-dilution type biological nitrification and denitrification process, which is no different from the technology that was widely used before the advent of membrane separation methods.

■ The process of coagulating and separating biologically nitrified and denitrified water and adsorbing it on activated carbon is also the same as the conventional technology, and no improvements have been made.

In short, the essence of the membrane separation method, which is currently recognized as the latest technology, is that UF membranes are simply applied to solid-liquid separation processes such as precipitation, which were used in processes before the advent of membrane separation methods. .

As a result, the current state-of-the-art UF membrane system does not solve the following serious problems.

(a) A non-dilution type biological nitrification and denitrification tank requires a large-capacity tank with a retention period of 10 days for the inflow of human waste, and its civil engineering costs, construction costs, and installation area are extremely large. This has been a serious problem since local governments, which are the users, are having difficulty acquiring land for human waste treatment facilities, and they do not necessarily have the financial means to do so.

(b) Since the nitrogen concentration of treated water (effluent) is determined only by the treatment results of the biological nitrification and denitrification process, biological nitrification is necessary to maintain good effluent quality at all times. The denitrification process requires careful and precise operational management. Therefore, skilled technicians are not always available, and operation management is difficult for urine treatment facilities.

Moreover, even with such careful operation, there are many unknowns about the behavior of microorganisms involved in nitrification and denitrification, and if the nitrification and denitrification reaction deteriorates, it will take a long time to recover. However, during that time, treated water whose quality has deteriorated must be discharged into public waters. This is a very big problem.

(C) Due to aggregation by FeC1 or Alum, Fe(OH)* or Al(OH), which is difficult to dehydrate,
A large amount of sludge mainly composed of 3 is generated.

(d) Since activated carbon adsorption is essential, the regeneration operation of waste activated carbon is complicated. The operating cost of activated carbon adsorption treatment itself is also high.

<Problem to be solved by the invention> The present invention solves the above-mentioned conventional state-of-the-art technology (UF membrane separation method).
The objective is to provide a new process that can completely solve the drawbacks (a) to (d).

Means for Solving the Problems> The present invention provides a step in which nitrifying bacteria and denitrifying bacteria are allowed to exist in human waste water to advance biological nitrification and denitrification, and the effluent from the step is filtered through an ultrafiltration membrane or A process of solid-liquid separation into membrane-separated sludge and membrane-permeated water using a precision filtration membrane, a process of subjecting the membrane-permeated water to reverse osmosis treatment using a reverse osmosis membrane, and separating it into reverse osmosis membrane concentrate and reverse osmosis membrane-permeated water, and reverse osmosis. The membrane concentrate solution is
This method of treating organic wastewater is characterized by comprising a step of biologically nitrifying H and -N and then evaporating to dryness.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

Adding a flocculant 2 (a cationic polymer or a combination of a cationic polymer and an anionic polymer is preferable) to human waste 1,
After forming strong and large flocs, the flocs are fed to a fine-mesh screen 3 (preferably a rotary wedge wire screen with a mesh size of about 0.5 to 1 mm), and the agglomerated flocs are separated by the screen.

4 is flocculated sludge separated by screen 3;
Since the fibers contained in human waste 1 coexist within the floc, it has excellent dehydration properties and can be easily dehydrated to around 60% moisture using a screw press.

5 is human waste separated by a screen, and most of the SS and colloidal substances have been coagulated and removed, so human waste 1
The BOD is about 2, 5000■/! It has declined to a certain extent. The screen-separated human waste 5 is supplied to a crushed urine storage tank 6 and stored therein. The capacity of the storage tank should be set to 4 to 5 days worth of human waste brought in per day. 2 days worth.").

The role of the conventional human waste storage tank was to simply absorb and average daily fluctuations in the amount of imported human urine, but in the present invention, preferably, the storage tank 6 contains nitrifying bacteria and denitrifying bacteria ( (hereinafter referred to as nitrifying/denitrifying bacteria), air is actively supplied from the air diffuser 7, and the screen-separated urine 5
By effectively utilizing the time while B is stored in the storage tank,
Most of the OD and nitrogen components are removed. This is one of the important features of the invention.

As a result of experiments, it was confirmed that approximately 95% of the BOD and nitrogen components of the coagulated and separated human urine were removed when sufficient air was supplied to the storage tank 6. Additionally, subsequent ultrafiltration (UF
) membrane or microfiltration (MP) membrane 8 was also found to improve the membrane separability of the membrane separation process.

Therefore, the liquid in the storage tank 6 is pumped to the UF membrane or the MF
The water is fed under pressure to the membrane 8, and the nitrifying and denitrifying bacteria grown by aeration in the storage tank 6 are completely separated through the membrane, and separated into membrane-permeated water 9 with zero SS and membrane-separated sludge 10.

A part of the H-separated sludge 10 is returned to the storage tank 6 as return sludge 10a, and the other part of the sludge 10 is surplus activated sludge 10b.
Addition of flocculant 2 to incoming human waste 1 and screen 3
It is supplied to the first stage of the coagulation separation process consisting of separation by , and is coagulated and separated together with human waste 1.

Thus, the UF membrane permeated water 9 is pumped to a reverse osmosis (RO) membrane 11 by a high-pressure pump, and subjected to reverse osmosis treatment to remove organic matter, salt, nitrogen components such as NHs-N, and color remaining in the UF membrane permeated water 9. The membrane is separated by the principle of reverse osmosis.

12 is RO membrane permeate water, 13 is RO membrane concentrated liquid, R
Approximately 175 to 1 of the flow rate of the UF membrane permeate water 9 supplied to the O membrane
/10 concentration.

Reference numeral 14 denotes an aeration tank for biologically nitrifying NH3-N contained in the RO membrane concentrate 13 containing a high concentration of color and salt. In order to promote the nitrification reaction in this aeration tank 14,
It is highly preferred to add a portion 10c of the membrane separated sludge 10. 15 is air for nitrification.

The RO membrane concentrate 13a in which the nitrification of N1 (3-N) has been completed is supplied to the evaporation drying step 16 and disposed of.

The function of the nitrification aeration tank 14 is very important, and if this step is omitted, water vapor containing NH3 gas will volatilize during the evaporation drying step 16, and secondary pollution will not be caused.

Although biological nitrification and denitrification are preferably carried out in the storage tank 6, they may be carried out afterwards as in the conventional manner.

[Example] An example of the results of an experiment according to the flow shown in FIG. 1 will be described below.

After mixing surplus activated sludge 10b with the imported human waste having the water quality shown in Table 1, a cationic polymer (Evagrowth C104
When 250 μ/l of G, Ebara Infilco Co., Ltd. product) was added and stirred for 1 inch, strong and large flocs were formed, and when fed to a rotating fine-mesh drum wire screen (1 mm opening), the polymer agglomerated. The flocs could be easily separated using a screen, and the screen-separated human urine shown in the right column of Table 1 was obtained.

Table 1 This screen-separated human waste is stored in a filtered human waste storage tank (capacity for storing human waste for 5 days), and air is removed so that the dissolved oxygen in the liquid in the storage tank is 0.3 to 1.0 ■/I! , supplied with aeration to be maintained. A large amount of nitrifying and denitrifying bacteria were growing in the screen-separated human waste that had been aerated in the storage tank for 5 days. This is carried out using an ultrafiltration membrane separation device (nominal fractionation molecule ff1lo
(10,000 membrane material polysulfone, using a tubular module with cross-flow membrane separation method).
When passed through the membrane, UFII had the water quality shown in Table 2.
9 permeated water was obtained.

Table 2 Next, the UF membrane permeated water having the water quality shown in Table 2 was adjusted to a PTT of 5.0 to prevent scale formation, and subjected to reverse osmosis (RO).
UF membrane permeate water is supplied to the membrane and subjected to reverse osmosis treatment at a flow rate of 1
It was concentrated to 76. The RO membrane used had a salt rejection rate of 98%.

Table 3 shows the quality of the RO membrane permeate water.

Table 3 Next, when the RO membrane concentrate containing 350 to 420 mg/i of NHff-N was aerated for 24 hours in the coexistence of nitrifying bacteria, the NH and -N in the RO membrane concentrate decreased to less than 10 mg/l. However, there was no problem in which ammonia gas was generated during the evaporation drying process (using a drum dryer) of the RO membrane concentrate and dissipated into the atmosphere.

<Effects of the invention> ■ The removal of nitrogen components from human waste does not rely solely on biological nitrification and denitrification as in conventional methods, but rather uses a purely physicochemical means called an RO membrane, resulting in improved treatment effects. It is reliable and operation management becomes much easier. In the conventional method shown in Figure 2, the nitrogen concentration in the effluent depends only on the treatment results of the biological nitrification and denitrification process, and therefore requires careful and skilled maintenance, but the method of the present invention uses an RO membrane. Since nitrogen removal is also used, no skilled technicians are required.

■ Alum, FeC after biological nitrification and denitrification process
Since a coagulation separation process such as 1= is unnecessary, coagulated sludge that is difficult to dewater is not generated.

■ Since activated carbon adsorption treatment is not required, the complicated operation of regenerating activated carbon is no longer necessary, and maintenance is easy.

■ The biological nitrification and denitrification process (10 days of human waste retention) that precedes the UF membrane separation process of the conventional method (Fig. 2) is no longer required, so the installation area and construction costs can be significantly reduced, and human waste processing It can provide an extremely desirable system for local governments that are struggling to acquire land and secure budget for facilities.

As a result of the above-mentioned effects, it is possible to significantly improve the conventional method in all aspects, including ease of maintenance, stability of effluent water quality, installation area, and construction cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a flow sheet of the present invention, and FIG. 2 is a diagram showing a flow sheet of the latest conventional membrane separation method. Explanation of symbols

Claims (1)

[Claims] A step in which nitrifying bacteria and denitrifying bacteria are present in human waste wastewater to advance biological nitrification and denitrification, and the effluent from the above step is solidified into membrane-separated sludge and membrane-permeated water using an ultrafiltration membrane or a microfiltration membrane. A step of liquid separation, a step of subjecting the permeated water to reverse osmosis treatment with a reverse osmosis membrane to separate it into a reverse osmosis membrane concentrate and a reverse osmosis membrane permeated water, and a step of separating the reverse osmosis membrane concentrate into NH_3-N contained in the liquid.
A method for treating organic wastewater comprising the steps of biologically nitrifying it and then evaporating it to dryness.