JPS63200899A - Process for treating organic filthy water containing phosphate ion - Google Patents

Abstract

PURPOSE:To reduce concentration of PO4<3-> ion in permeated water through permeable membrane by adding Mg ions to org. filthy water contg. phosphate ions, treating then the water biologically, adding Al ions to the biological treating stage or to slurry discharged from the stage, and separating the PO4<3-> ions using membrane. CONSTITUTION:After adding Mg ions 2 to org. filthy water contg. phosphate ions, the filthy water is treated biologically in a biological treating stage 3. After adding further Al ions or Fe ions 5 to the biological treating stage or the slurry 4 discharged from the stage 3, solid in the water is separated from liquid with a membrane separation apparatus 6 into clean permeated water 7 contg. no SS and concentrated separated slurry 8. Thus, the concn. of PO4<3-> is reduced remarkably, so a removing stage of PO4<3-> by adsorption is no more necessary, or frequency for regenerating adsorbent is reduced extremely even if the adsorption stage of PO4<3-> ion is executed additionally. Accordingly, disposal of regenerated waste liquid is facilitated extremely because crystallization or centrifugal separation, etc. Which has been required conventionally, is unnecessary.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for treating organic wastewater containing phosphate ions (PO4ff-) such as human waste water, sewage, and various wastewaters, and particularly to a biological treatment process. The present invention relates to an improvement in a treatment method including a membrane separation step.

[Conventional technology]

Conventionally, biological treatment methods such as activated sludge methods have been most widely used to treat organic sewage, and settling tanks have been used to separate activated sludge and treated water.

However, recently, activated sludge can be directly processed using UP II! without installing a settling tank. The solid-liquid separation method has been put into practical use in the field of gray water and human waste treatment.
Among these, in order to treat organic wastewater containing high concentrations of PO,'-, such as human waste, wastewater is subjected to biological treatment and then membrane separation, and the permeated water is treated with activated carbon adsorption treatment and treated with hydrated zirconium oxide (Zr). PO2 by (h・n11g0)
A process was proposed in which - was adsorbed and removed (refer to the collection of abstracts from the February 1988 National Cities TLT Cleaning Conference Research Presentation).

[Problem that the invention seeks to solve]

However, in such a conventional process, the following problems remain unresolved, and it must be said that it is far from an ideal process.

■ In membrane separation such as UP membrane, most of r'o and '- pass through, so an adsorption removal process using PO4''-adsorbent (ZrOz -nHlo) must be provided for Mi3 water flow. , when the concentration of PO4'- to be adsorbed and removed is high (in the case of human waste treatment, the concentration of POa'- in the water permeated through the UF membrane reaches as high as 500 to 600 ■/l), PQ
The a'-adsorbent quickly reaches a saturated adsorption amount.

As a result, frequent regeneration operations are required, maintenance is troublesome, and operating costs are high.

■ Moreover, PO43− adsorbed on Zr0t・nHt
In order to remove and regenerate the Na0HtI solution, it is brought into contact with the Na0HtI solution, but as a result, a large amount of regeneration waste liquid containing a large amount of Na2PO4 is generated.

In order to treat this recycled waste liquid, Na3P is extracted from the recycled waste liquid.
Although O4 crystals are crystallized, separated using a centrifuge, etc., and discharged from the system, these operations are complicated, and there is also the problem of what to do with the recovered Na3PO4.

The purpose of the present invention is to fundamentally solve the problems of such conventional processes. Significantly reduces the regeneration frequency of the removal process.

(o) Eliminates the need to dispose of Po,3-adsorbent regeneration waste liquid.

This is the problem to be solved.

[Means for solving problems]

As a means for solving the above-mentioned problems, the present invention provides biological treatment after adding magnesium ions to organic wastewater containing phosphate ions, and treating the slurry in or out of the biological treatment process with magnesium ions. The present invention provides a method for treating organic wastewater containing phosphate ions, which is characterized by adding aluminum ions or iron ions and performing membrane separation.

[For production]

The effects of the present invention will be explained below with reference to drawings showing one embodiment of the invention, taking human waste, which is a typical example of organic sewage containing phosphate ions, as an example. Magnesium ion CM in night soil,”)
2, for example, a compound that dissociates H, R- (Mg(OH)
t, MgO, MgCl1. After adding Mg5O*, etc.), the mixture is led to biological treatment step 3.

The amount of Mgz′″2 added is 1 in molar ratio to PO43-.
The above is good. By adding Mg", most of the P04'- in human urine reacts with Hgto, and Mg"+
Po,3−+Nl,”→NHJgPO4↓ occurs, and magnesium ammonium phosphate (Na3
PO4) is converted into the same phase as a precipitate. Then, in the biological treatment step 3, BOD components, COD components, etc. are removed from the human waste l containing this NH4MgPOn precipitate.
Since nitrogen content remains in the human waste, the third biological treatment step is preferably a biological nitrification and denitrification step.

In this biological nitrification and denitrification process, BOD components, CO
The D component, nitrogen content, etc. are removed, but the inventor discovered the following very interesting phenomenon during the course of the experiment.

That is, the present inventors believe that MHz-N in human waste is due to nitrification that exists in high concentrations during the biological nitrification and denitrification process.
As a result of being oxidized to O, -N or N0s-H, the Nt14° concentration in the process becomes a very low level of several ■/i, and NHaMgPOi precipitates form the following chemical equilibrium relationship, NHJg
We expected that most of it would be redissolved by the reaction of POa j → NH*""Mg" + PO43-, but the experimental results were contrary to our expectations;
It was observed that even if the HnMgPO4 precipitate was retained for a long time in the biological nitrification and denitrification process, only a portion of the precipitate was dissolved and the HnMgPO4 precipitate was not completely dissolved. This means that
Activated sludge slurry flowing out from biological nitrification and denitrification process 4
This was confirmed because a large amount of NIIJgPO4 microcrystals were contained in the sample.

Note that the addition point of yj g l -2 may be a denitrification tank part in the biological nitrification and denitrification process.

Next, the activated sludge slurry 4 flowing out from the biological treatment process 3 is treated with aluminum sulfate, polyaluminum chloride, etc. to remove aluminum ions (^I'') or ferric chloride,
By adding iron ions (Fe34) 5 using polyferric sulfate, etc., 204'- contained in the method in activated sludge slurry 4 is converted into precipitation of aluminum phosphate (AIPO4) or phosphoric acid 2t&(FePOa). , activated sludge flocs together with microfiltration (MF) membranes, ultrafiltration (O
F) Solid-liquid separation is performed by a membrane separator M6 equipped with a membrane or the like to separate extremely clear membrane permeated water 7 with zero SS and concentrated separated slurry 8.

Most of this concentrated and separated slurry 8 is recycled to the biological treatment process 3 as return slurry 9, and the remaining part is sent to the sludge treatment process (not shown) as surplus slurry IO.

In the excess slurry lO, NHJgr'% precipitate and AlPO
4 precipitate or FePOn precipitate, and the present invention is characterized by the technical concept of discharging POe- contained in wastewater as two types of phosphoric acid-containing precipitates to the outside of the system together with excess slurry 10. have. Conventionally, Po, 3- in organic sewage was treated as NHaMgPOn precipitation, AIPO* sedimentation or FePO by the treatment according to the present invention.
There is no technology that removes P as 4-precipitate or as P incorporated into biological cells.

On the other hand, since the membrane i3 permeated water 7 has a PO43- value of 10 w/J or less, it can be discharged as is 7', but if desired, it can be led to the phosphoric acid adsorption and removal step 11 and the membrane permeated water 7 After adsorbing and removing the residual POe-, the effluent water 1
The phosphoric acid adsorption remover used may be 2.
It can be appropriately selected from known iron hydroxide, bone char, activated alumina, hydrated zirconium oxide, hydrated titanium oxide, and the like.

To regenerate the phosphoric acid adsorption remover that has adsorbed po,"-, use an alkaline agent such as Na0ILMg(011)t1
By bringing 3 into contact with each other, it is possible to easily remove PO and t. As a result, the emitted po,'
In order to dispose of the alkaline recycled waste liquid 14 containing a high concentration of
This is easily possible by converting NH<MgP(:h and AIPO, or PePOa) into a solid phase using I'' or pe2+5.For this purpose, operations such as crystallization and centrifugation on the regenerated waste liquid 14 as in the conventional process. becomes unnecessary.

〔Example〕

Experiments were conducted as follows based on the illustrated flow of the present invention.

Magnesium hydroxide is added to the filtered human urine showing the water quality shown in Table-1.
000■/1 as Mg" and stirred,
Nitrification liquid circulation type biological nitrification and denitrification process (second denitrification tank,
(consisting of a nitrification tank, a second denitrification tank, and a reaeration tank), activated sludge MLS 314000 / 1, residence time 1
It was set to 0 days.

Table 1: Sludge removal and urine water quality Analysis of the solubility of poa3-tm contained in the activated sludge slurry discharged from the re-aeration tank located at the final stage of the biological nitrification and denitrification process revealed that it was 30-45 ■/1
, and the PO4'-concentration in the inflow-removed human urine is 960*/l
The PO-1 in the human waste was largely removed as NIl, MgPO, and precipitates, and was also incorporated into the activated sludge.

Next, 800-1000 μ/l of aluminum sulfate was added to the activated sludge slurry flowing out from the above-mentioned reaeration tank, and after flocculation treatment under the conditions of ρμ 5.8-6.1, When solid-liquid separation was performed using a ten-man tubular type UF membrane (manufactured by Nitto Denko), the water quality of this UF membrane permeated water was shown in Table 2.
As shown in Figure 2, extremely clear treated water that can be discharged was obtained.

Below is a margin table - 2 UF membrane i3 water quality [Effects of the invention] As described above, according to the present invention, the following extremely important effects can be obtained.

■ The PO1'- concentration in the membrane-permeated water obtained through membrane separation can be significantly reduced compared to conventional processes, so the subsequent PO4
3- It is possible to eliminate the need for the adsorption removal step, or even if a PO4'-adsorption step is provided, the frequency of regeneration of the adsorbent can be extremely reduced, and the disposal of regenerated waste liquid can also be done by crystallization, which was previously required. This eliminates the need for operations such as centrifugation and centrifugation, making it extremely easy.

■ Crystalline precipitation reaction of NHsMgPO* by addition of Hgt* and AlPO by addition of A13゛ or Fe1
As a result of utilizing both the 4 and FePOn precipitation reactions in a new manner, the required addition amount of AI" or Fe" can be reduced, thereby eliminating bulky hydroxylation that is troublesome during 1η mud treatment. The generation layer of aluminum sludge or iron hydroxide sludge can be reduced.

■ Dense crystalline NI14 is present in the discharged surplus slurry.
Since MgPOn precipitates coexist, concentration and dewatering properties are improved (and sludge treatment can be streamlined).

[Brief explanation of the drawing]

The drawing is a flow sheet showing one embodiment of the invention. 1... Human waste, 2... Magnesium ion, 3...
Biological treatment process, 4... activated sludge slurry, 5... aluminum ions or iron ions, 6... membrane separation device, 7
...II￥permeated water, 7'...discharge, 8...concentrated separation slurry, 9...return slurry, 10...surplus slurry, 11...phosphoric acid adsorption removal process, 12...・Discharged water,
13... Alkaline agent, 14... Recycled waste liquid.

Claims (2)

[Claims] (1) Magnesium ions are added to organic wastewater containing phosphate ions, followed by biological treatment, and aluminum or iron ions are added to the slurry flowing out from or within the biological treatment process for membrane separation. A method for treating organic wastewater containing phosphate ions. (2) The method for treating organic wastewater containing phosphate ions according to claim 1, wherein the biological treatment is biological nitrification and denitrification treatment.