JPS61278309A - Purification of water - Google Patents

Abstract

PURPOSE:To perform effective flocculation of contaminant in water without requirement for neutralization even if the alkalinity of the water is <=10ppm by using an inorg. potassium aluminate type compd. as flocculating agent for a flocculation-settling stage of water. CONSTITUTION:An inorg. potassium aluminate type compd. such as KAlO3 is used as flocculating agent for a flocculation-settling stage of water. For example, contaminated water 1 is pumped up to a well 3, treated by pre-charged chlorine 4, transferred to a mixing basin 5 where flocculant soln. of an inorg. potassium aluminate type compd. is added to the water from a flocculant soln. tank 6 and stirred. The water is then delivered to a flocculation-settling basin 8 where the flocculated material is settled. Settled sludge 8A is transferred to a sludge treating section and the water is purified by passing through a high speed filtration basin 9. The purified water is transported to a purified water basin 10 and stored.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for purifying water, and particularly to a technique for flocculating pollutants in water.

[Background technology]

The rapid development of industry and the improvement of people's lives have significantly increased the amount of industrial water and tap water used, and water pollution problems have arisen in various places.As a result, sewage treatment has become a focus of attention. ing.

Even if advanced biological separation membrane treatment, depth filters, screen filters (membranes, microfilters), etc. are used, supernatant water must be treated by sedimentation or floating sludge treatment using a flocculant as a pre-treatment. Can not.

The flocculants used in the flocculant treatment are broadly classified into organic and inorganic types. Examples of inorganic flocculants include:

Examples include polyaluminum chloride, polyferrous sulfate, ferrous sulfate, ferrous sulfate, ferric chloride, and aluminum sulfate.

However, all of them have a problem in that they are main flocculants with an acidic value in the range of PH 0.3 to 6.0, and require an alkali neutralizing agent.

[Purpose of the invention]

An object of the present invention is to provide a technology for treating flocculent precipitates using a main flocculant that does not require neutralization and has good flocculation stability even when the alkalinity is 10 degrees or less. .

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief summary of five representative inventions among the inventions disclosed in this application is as follows.

That is, in a water purification method that includes a step of treating underwater pollutants with flocculent precipitates, an inorganic aluminate compound, or an inorganic aluminate compound and polyaluminum chloride are used as a flocculant in the flocculent precipitate treatment step. By coagulating and separating pollutants using

Even when the alkalinity is 10 degrees or less, neutralization is not necessary and it is possible to efficiently coagulate pollutants in water.

Examples of the water purification method of the present invention will be described below.

In addition, in all the figures for explaining an example.

Components having the same function are given the same reference numerals, and repeated explanations thereof will be omitted.

〔Example! ]

FIG. 1 is a schematic diagram showing a schematic configuration for explaining Example I in which the water purification method of the present invention is applied to a water treatment facility.

In Fig. 1, 1 is wood containing pollutants, which is pumped up to a landing well 3 by a pump 2, and after adding pre-chlorine 4, it is sent to a mixing pond 5, and from an inorganic aluminate compound flocculating solution tank 6. The inorganic aluminate compound flocculating solution is added and stirred by the pump 7, and is transported to the flocculent precipitate (hereinafter referred to as floc) pond 8 to form flocs, followed by sedimentation and separation. The liquid is transported to a sludge treatment plant (not shown), and other liquids are purified through a high-speed filtration tank 9, and then transported to a water purification tank 10, where water is stored. Water is distributed to various parts from this water purification pond IO.

The main components of the inorganic aluminate compound aggregation solution are:

An inorganic aluminate compound (for example, KAQ○2),
The outline of the aggregation effect of polyvalent metal ions by the aqueous solution is 1.
It is expressed by the following formula.

n K A Q O2+ 2 H20 −+n CAQ” +3 (OH−))+nKOH4
XKA1 yM" ・z(OH)+5iOz +A(1
(OH)s+'KOH However, M is an abbreviation for alkali metal or alkaline earth metal, and the arithmetic numeral on the upper right side indicates the valence.

Further, n is a natural number, and x, y.

2 is a metal for forming a double salt.

In this way, a coprecipitated floc of water pollutants is formed.

A group of anions are arranged around each cation, forming a coordination polyhedron.

Inorganic aluminate compounds of alkali metals and alkaline earth metals have large electrical induction and show electropositivity. Alkaline earth metal compounds easily lose one S electron in their outermost shell and become monovalent cations, which interact with many pollutant elements and compounds. Create intermetallic compounds and crosslink the flocs.

The distance between a cation and anion is determined by the sum of the ionic radii, and the coordination number, that is, the number of anions that are closest to each other around the cation.

Determined by the radius ratio of cations and anions. The radius of -valent metals, especially di' cations, is larger than the radius of the surrounding water ions OH-, so they are surrounded by many anions.They are responsible for stabilizing the dispersion of turbid substances in water. It contributes to the neutralization of the repulsive negative charge (-) on the turbid surface.In a stable structure, the total binding force of the valence bonds connecting an anion and all nearby cations is equal to the sum of the anion's charges. Because it is equal to 1.45 angstroms, the suspended solids that are dispersed and stabilized in water are usually not easily disassembled. Even when hydrated, the surface type decreases quickly.

In addition, alkaline earth metals are also electropositive, second only to alkali metals, and have a large effect. Both the oxide and the hydroxide of the base aluminum are amphoteric, but the polyvalent metal inorganic aluminate compound is water-soluble and alkaline. In this aqueous solution (7)H(Al1(OH)4 (H20)2
), H:t (AQ(oH)a)'' ions also neutralize the repulsive negative charge (-) on the surface of the parent wood colloid, which is the cause of stabilizing the turbidity dispersion.

A single particle suspended in water generally has a negatively charged (-) surface, and its electrostatic repulsion prevents it from binding and stabilizes its dispersion. If a substance with the opposite potential (+) necessary to neutralize these repulsive negative charges (-) is added, the surface potential of the particles (
zeta potential) decreases, making it easier to bond. This is done through a process in which the resulting fine aggregated suspension is further coarsened by crosslinking, so the ions contained in the flocculant have a high positive charge (+), and positrons are generated to stabilize the crosslinking. It requires recombination and is required to have the lowest ionization potential and be the most electropositive of the elements. Here, the inorganic aluminate compound of the valent metal fills this.

Multivalent ions of aluminum overlap.

In addition, water molecules are adsorbed to the surface of hydrophilic particles such as colloids, and are protected by a surface hydration layer, making them difficult to bond with. In this case too, by adding positively charged substances (metal ions and positively charged polymers).

The particles bond together due to a decrease in surface potential, blockade of parent wood groups, electrostatic colloid bonding, etc.

Next, the amount of ions (critical aggregation concentration) and aggregation in the aggregation process will be explained.

As the valence of the flocculant ion increases from monovalent to tetravalent,
- If the value is "1", then ro, o 16J for divalent, and rO,o for trivalent.
014'', and in the case of tetravalent ones, it can be theoretically derived that the amount is significantly less than 0゜00024J.This is also known empirically as the Schulze-Hachidy law.In this respect, inorganic aluminium Double salts of acid compounds are extremely effective because they already contain large amounts of tetravalent and trivalent cation species and electrically strong positives.

However, the growth of flocs due to the bonding of particles is limited by the surface potential lowering effect alone, and it takes time, so it is not possible to form huge flocs. Therefore.

The cross-linking between suspended solids is achieved by highly polyvalent ions generated when aluminum ions in the flocculant are hydrolyzed in water, or by solid aluminum hydroxide and other metal hydroxides. The speed of formation, affinity for the surface of suspended solids, adsorption activity, etc., coarsening of suspended solids,
In other words, it has a large effect on the precipitation rate.

Thus, the inorganic aluminate compound flocculant is a basic flocculant and does not require alkali neutralization. And the standard usage amount is 20ρpIII ~ 200pp
Since the amount used is small like m, the pH of the wastewater can easily be 5.
．． It can be adjusted within the range of 8 to 8.6, and since it does not contain chloride, there is no risk of corroding facility metals.

Here, the inorganic aluminate compound aggregation solution used in the practical test was an inorganic aluminate compound, for example, [KA
It is a 50% aqueous solution containing Q 02 ]n as the main component, a reddish-brown liquid, specific gravity (21°C) 1.44-1.46, P
H (Ig/10.0■Q, 21°C) 11-13, freezing temperature -50°C or lower.

The characteristics of this inorganic aluminate compound aggregation solution are as follows.

(1) Demonstrates excellent aggregation speed even in low-temperature environments.

(2) It is the most electropositive among molecules (negative charge negativity) and has the greatest interaction with other elements and compounds.

(3) It has a low freezing point, so it does not freeze even in cold regions.

(4) Since it does not contain chlorides, it will not corrode iron or other metal parts. Also, there is no synthesis of harmful organic chlorine.

(5) Because of its basicity, it has great hydrophilicity and homogeneous catalytic properties;
When the reactant is dissolved in the solvent (flocculant), it forms a homogeneous phase and the reaction proceeds.

(6) It is difficult to form a transition metal complex phase, and there are also homogeneous catalytic reactions and transition metal complexes in which the transition metal is coordinated and its children are coordinated. A vacant coordination site is created by dissociation of some of the children. It has a unique effect in which the reaction progresses by coordinating the reaction substrate to the coordination site, which has a large electrical coagulation effect. General ionization is accelerated.

The main uses of this inorganic aluminate compound coagulation solution are water treatment, industrial water treatment, sewage treatment, and industrial wastewater treatment (*iron,
For water treatment such as automobile industrial wastewater treatment, paper wastewater treatment, glass manufacturing wastewater treatment, gravel wastewater treatment, other factory wastewater treatment), recovery of valuable substances (recovery of metal copper powder, silver, etc.), protein, animal and vegetable oils. It is used for cleaning stains caused by oxidation.

Next, an experimental example using the inorganic aluminate compound aggregation solution of Example 1 will be shown.

FIG. 2 is a diagram showing the experimental results for a sample of animal fat suspension, pH: 6°8.

Figure 3 shows the turbidity of 9.0. PH; 7°1, alkalinity 44
It is a figure showing the experimental results of the turbidity removal effect on low turbidity water.

Figure 4 shows suspended solids (hereinafter referred to as SS); 950 ppm
, PH: 5.4, is a diagram showing the results of a lower grade paper white precipitation rate test when a 50% aqueous inorganic aluminate compound aggregation solution was added to raw water with a pH of 5.4.

FIG. 5 shows SS i 1700 ppm, PH; 6.
FIG. 3 is a diagram showing the results of a gravel wastewater sedimentation rate test when a 50% aqueous inorganic aluminate compound aggregation solution was added to the raw water of No. 3.

FIG. 6 is a diagram showing the results of a precipitation rate test of zinc sulfate liquid impurities when a 50% aqueous inorganic aluminate compound flocculation solution was added to raw water with SS: 15000 ppm and PH: 4.0°. .

[Example ■]

FIG. 7 is a schematic diagram showing a schematic configuration for explaining Example 2 in which the water purification method of the present invention is applied to a sewage separation pressurized flotation tank treatment facility in a factory.

In FIG. 7, reference numeral 11 denotes a raw water tank for storing wastewater containing pollutants, which is pumped up to a flocculation floc tank 13 by a pump 12, and then pumped from an inorganic aluminate compound flocculation solution tank 14 to an inorganic aluminate compound flocculation solution by a pump 15. After adding and stirring to form flocs, pressurized water tank 17
The mixed water is mixed with pressurized water from the tank and conveyed to the pressurized separation flotation tank 16.

In the pressurized separation flotation tank 16, the sludge chute guide member 1B
The sludge sedimentation separation is promoted by the sludge scraper 18A, and the sedimented sludge is separated.

Sludge chute guide member 18 and residual sludge sedimentation accumulator 1
9 and transported to the sludge tank 20. On the other hand, the treated purified water 21 is transported to a purified water receiving tank 22, and is supplied to various parts as recycled water from the purified water receiving tank 22, which is designed to store water. Further, this treated purified water 21 is mixed with well water or tap water 25 and supplied to the pressurized water tank 17 .

The sludge in the sludge tank 20 is sent to a sludge dehydrator 24 by a pump 23, where it is dehydrated and transported as sludge cake. The wood dewatered by the sludge dehydrator 24 is drained and transported to the raw water tank 11 again. Further, the surplus water supplied and diluted by 25 is drained by a drain pipe 26. In the figure,
B is a valve and P is a pump. Next, the results of an experimental example using this example will be shown.

Figure 8 shows chrome plating and reducing agent Na2SOs.

FIG. 2 is a diagram showing the results of a plating wastewater sedimentation rate treatment test when a 50% aqueous inorganic aluminate compound aggregation solution was added to raw water with a turbidity of 180 degrees, a pH of 6.2, and a water temperature of 15 degrees Celsius.

Figure 9 shows that 1100 pp of a 6% aluminum sulfate solution was added to gravel washing wastewater with SS; 3% and pH: 6.5.
It is a figure which shows the result of the turbidity test when the inorganic aluminate compound aggregation solution of 0% aqueous solution was added.

[Example ■]

The following Table I shows the experimental results of Example 2 in which the water purification method of the present invention was applied to a paperboard comprehensive wastewater coagulation flotation treatment.

[Example ■]

The water purification method of the present invention is applied to excess sludge (decanter dehydration, PH; 7.1. SS: 19,
The experimental results of Example (2) applied to the treatment (500ppta, VTS; 6g%) are shown in Table (2).

[Example ■]

The experimental results of Example V, in which the water purification method of the present invention was applied to cleaning protein, animal and vegetable oil stains, are shown in the following Table 2.

Incidentally, by adding a small amount of sodium nitrite as a rust preventive agent to the inorganic aluminate compound solution in Example 2 above, metal pipes and the like can be prevented from rusting at the same time.

[Example ■]

The water purification method of this embodiment (2) is a water purification method that includes a step of treating water pollutants with flocculent precipitates.
This method is characterized in that an inorganic aluminate compound and polyaluminum chloride are used together as the flocculant for floc treatment to flocculate and separate the pollutants.

For example, turbidity: 25°, PH: 7.1. When the polyaluminum chloride shown in Table 1 and the 50% aqueous solution of the inorganic aluminate compound shown in Table 2 were added to river water at a water temperature of 3°C, the experimental results are shown in Table 2.

Also, river water with high turbidity 1, for example, turbidity; 550°, PH
7.1. When polyaluminum chloride; 40 ρpat was added to river water at a water temperature of 17°C, and the amount of inorganic aluminate compound solution of 580% aqueous solution was increased,
A characteristic curve as shown in FIG. 10 is obtained.

If so, the above example! Contaminants in the water can be coagulated more efficiently than in the case of ~■.

Although the present invention has been specifically explained above with reference to Examples, the present invention is not limited to the above-mentioned Examples, and it goes without saying that various changes can be made without departing from the gist thereof.

〔effect〕

As explained above, according to one aspect of the present invention, in a water purification method that includes a step of flocculating pollutants in water, an inorganic aluminate compound is used as a flocculant in the flocking step to coagulate and separate the pollutants. As a result, even when the alkalinity is 10 degrees or less, neutralization is not necessary and the aggregation of pollutants in the water can be carried out efficiently.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a schematic configuration of an implementation facility for explaining Example I in which the water purification method of the present invention is applied to a turbidity separation and sediment treatment facility for river water, etc. at a water supply plant; Figures 6 through 6 are diagrams showing the experiment and results of Example I. Figure 7 illustrates Example 2 in which the tree purification method of the present invention is applied to a sewage separation pressurized flotation tank treatment facility in a factory. FIG. 8 and FIG. 9 are diagrams showing the experimental results of Example (2). FIG. 10 is a diagram showing the experimental results of Example (2).

Claims (2)

[Claims] (1) In a water purification method that includes a step of treating underwater pollutants with flocculent precipitates, the pollutants are coagulated and separated using an inorganic aluminate compound as a flocculant in the flocculent precipitate treatment step. A water purification method characterized by: (2) In a method for purifying water that includes a step of treating pollutants in water with flocculent precipitates, an inorganic aluminate compound and polyaluminum chloride are used together as a flocculant in the flocculent precipitate treatment step. A water purification method characterized by coagulating and separating substances.