JPS61118184A - Treatment of purified water - Google Patents

Abstract

PURPOSE:To remove efficiently org. substances forming trihalomethane, etc. by adsorbing and removing most of water-soluble org. substances, odor, iron, manganese, etc. with activated carbon, adding chlorine, and then treating the water in iron-removing and manganese-removing equipment. CONSTITUTION:In a water purifying plant wherein an activated carbon filter basin is provided, chlorine is not added before the activated carbon filter basin, and chlorine is added, after most of water-soluble org.substances, odor, iron, manganese, and ammoniacal nitrogen are removed by adsorption and filtration with activated carbon. Iron-removing and manganese-removing equipment are provided, and the water is treated in the equipment. Consequently, org. substances forming trihalomethane, org. halogen compds., etc.-, can be removed efficiently and economically without deteriorating the efficiency in removing iron, manganese, ammoniacal nitrogen, turbidity, bacteria, etc. which are the objects to be removed in the present water purification.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a water purification method, and more specifically to a method for removing organic and inorganic substances in water using activated carbon and a process for removing inorganic substances by rapid sand filtration. .

(Conventional technology) Conventionally, water treatment methods performed at water treatment plants include pre-chlorination,
Currently, a treatment method that includes coagulation-precipitation treatment, rapid filtration treatment, and then post-chlorine treatment is generally adopted.

(Problem to be solved by the invention) Current treatment methods such as those mentioned above remove iron from raw water.

Although it can effectively remove manganese, ammonia nitrogen, ifi substances, bacteria, etc., it has little effect on removing organic substances, odors, etc. Also, organic substances in raw water react with the chlorine added during pre-chlorination treatment. Trihalomethane (hereinafter abbreviated as THM) and organic halogen compounds (hereinafter abbreviated as ↑OX), which are suspected to be carcinogenic, are produced as by-products, resulting in the deterioration of delicious water, which is the mission of waterworks. Safe water supplies are under threat.

By the way, chlorine during chlorination requires at least 9 times the amount of ammonia nitrogen, and when the ammonia nitrogen concentration is I PPM, 9 PPM or more of chlorine is required. The decomposition of ammonia nitrogen by chlorine proceeds within a short time.

Although the reaction ends, the production of TOX and THM by the 5 organic substances also proceeds rapidly, and as long as organic substances and chlorine coexist, TO
Since the reaction producing X and THM continues and increases, if the concentration of ammonia nitrogen is low, the amount of chlorine added can be reduced, and the initial production amount of TOX and TIIM may be suppressed. However, due to the presence of organic matter, concentrations of TOX and THM are high at the faucets of each household at the water supply end.

Organic matter and odor in water to solve this problem.

Activated carbon treatment is considered an effective method for removing THM and TOX. This activated carbon treatment is roughly divided into methods using powdered activated carbon and methods using granular activated carbon.In the former type of powdered activated carbon treatment, raw water is usually used to adsorb sorbed substances within a short time using the large surface area of activated carbon. 10 to 200 mg/1 (infiltration equivalent) is added to the water, and it is discharged out of the system together with other suspended solids in the coagulation sedimentation treatment step after the adsorption treatment.

Currently, it is used in many water treatment plants for the purpose of odor removal, but the treatment effect is not uniform because the treatment is easily affected by water temperature. It's also disposable
Since the cycle is not possible and the amount of sludge increases,
The disadvantage is that the processing cost is high. The latter granular activated carbon treatment involves passing water containing the adsorbed substance through a container or tower filled with activated carbon to adsorb the substance. This water flow method includes downward flow and upward flow, and fixed bed in the state of packed coal bed.

It is divided into fluidized bed and moving bed. When pre-chlorinated water is passed through a water treatment plant, activated carbon has a short lifespan when it comes to adsorbing THM, and there are many difficulties in practical use. Furthermore, when water is passed for a long period of time, the concentration of THM at the outlet of the adsorption tower becomes approximately 1.5 to 2 times the concentration at the inlet. That is, the activated carbon adsorption tower has the disadvantage that it acts as a THM breeder.

Instead of pre-chlorination treatment in which chlorine is added at the water intake or landing well, a similar phenomenon occurs with intermediate chlorination treatment in which chlorine is added immediately before the rapid sand filter, making it difficult to put it into practical use. In addition to the ammonia nitrogen and organic substances mentioned above, there are also metal ions such as iron and manganese. Unlike ammonia nitrogen and organic substances, these have a relatively slow reaction rate with chlorine, and the current water purification methods, which use pre-chlorination or intermediate chlorination, require rapid sand filters using manganese sand, etc. Although it can be removed to some extent, it is the cause of "red water" or "black water" in subsequent processes and ultimately in household faucets. When added, the disadvantage is that the coloring becomes more pronounced than when using the pre-chlorination method or the intermediate chlorination method.

(Means for Solving the Problems) In view of the drawbacks of the above-mentioned water purification treatment methods, the present inventors have discovered that iron, manganese, and
The purpose of the present invention is to provide a treatment method that can efficiently and economically remove organic matter that generates THM, TOX, etc. without reducing the removal efficiency of ammonia nitrogen, suspended solids, bacteria, etc. As a result of intensive study, water-soluble organic matter, odor, and manganese were found.

The present inventors have discovered that the above object can be achieved by adding chlorine after activated carbon filtration treatment, which adsorbs and removes most of the ammonia nitrogen, and then installing iron and manganese removal equipment.

That is, the present invention eliminates most of water-soluble organic matter, odors, iron, manganese, and ammonia nitrogen without adding chlorine in front of the activated carbon filtration tank in a water treatment plant equipped with an activated carbon filtration tank. This water purification treatment method is characterized in that chlorine is added after adsorption and removal by activated carbon filtration, and then iron and manganese removal equipment is installed for treatment.

In the treatment method of the present invention, the water flow method to the activated carbon adsorption tower may be either an upward flow or a downward flow, and as a filter material for iron and manganese removal equipment (rapid sand filtration pond) used after activated carbon adsorption treatment. Filter sand, manganese sand, manganese zeolite anthracite, etc.

Any material may be used as long as it can be used for removing iron and manganese.

(Function) In the present invention, iron and manganese in raw water are iron and manganese that form a complex with organic matter, and so-called inorganic iron,
Inorganic iron and manganese react quickly with chlorine and immediately become oxides that are easily adsorbed and removed by manganese sand, etc., but organic iron and manganese are easily oxidized by chlorine. The reaction is slow and cannot be removed by manganese sand or the like within a short period of time. However, most of the organic iron and manganese are adsorbed and removed when the water is passed through an activated carbon adsorption tower without the addition of chlorine, but the majority of the inorganic iron and manganese remain in the treated water without being adsorbed. In addition to this, it was also found that ammonia nitrogen exists in the form of ammonia nitrogen adsorbed on organic matter and inorganic ammonium ion, and the reactivity of the two to chlorine is almost the same. However, it was also found that ammonia nitrogen adsorbed to organic matter has good adsorption properties on activated carbon, while inorganic ammonia nitrogen remains in the treated water without being adsorbed.

(Example) EXAMPLES The present invention will be specifically explained below by giving examples.

TOC: Total organic carbon content (mg/II, by wet photooxidative decomposition method) TOX, Total organic halogen compound content (expressed as μg/C chlorine Ct amount, by coulometric titration method) TIIM;) Rehalomethane concentration (μg/ffi) , by SC method) THM-P i Free residual chlorine after 24 hours is 1 to 2
THM concentration after 24 hours when chlorine is added to PPM, (μg/l, FeH iron (A
lglI, by ICP method) Mn; manganese (Al
glI (by ICP method) NIl, 4; ammonia nitrogen (sg/j!, by coulometric titration method) Example 1. Comparative Example 1 Raw water for sex was taken and aluminum sulfate was added to I
After adding PPM and performing coagulation and precipitation treatment.

Rapid filtration treatment was performed at a filtration rate of 120 m/day. This filtered water was mixed with Cataler's granular activated carbon (product name - HA) 8-32.
LV = 10 m/downward flow in a tower packed with mesh
hr, and water was continuously passed under the conditions of 5V=lOhr-'. Sodium hypochlorite was added to this activated carbon-treated water so that the residual chlorine was 1.0 PP-, and then the water was passed through iron removal equipment with 60 cm of manganese sand laid at a filtration rate of 200 m/day.0Table-1 Total water flow through the granular activated carbon layer 1) 0,000
Raw water when water is passed through the bed, 'a settled water, activated carbon treated water,
The results of the final treated water are shown.

Table 1 For comparison, after adding sodium hypochlorite,
It was treated by the conventional method of passing through a rapid filtration basin with manganese sand. That is, sodium hypochlorite was added to the raw water taken in the same manner as in Example 1 so that the residual chlorine was I PPM, and then sulfuric acid band equivalent to AI 1.0 PPM was added and coagulated and precipitated. The water was passed through a rapid filtration basin made of manganese sand and then to an activated carbon adsorption tower under the same conditions as in Example 1. Sodium hypochlorite was added again so that the free residual chlorine became IPPM, and this was used as the final treated water. And so. In the same manner as in Example 1, the water quality in each step was measured when 10,000 beds of water were passed through the activated carbon adsorption tower. The results are shown in Table-2.

Table-2 Table 1) Table 2 shows the locations where chlorine was added this year.

N, D: Indicates non-detection.

(Effects of the Invention) The treatment method of the present invention eliminates the drawbacks of the conventional treatment methods as described above, by passing water to which chlorine has not been added to an activated carbon adsorption tower to absorb organic iron, manganese and ammonia. After nitrogen is adsorbed and removed, chlorine is added and passed through a rapid filtration basin made of manganese sand, etc., making it possible to easily remove iron, manganese, and ammonia nitrogen. Since most of the ammonia nitrogen is adsorbed by the activated carbon, the amount of chlorine required to be added can be significantly reduced, and at the same time, organic matter is also adsorbed and removed, significantly reducing the generation of TOX and TIFM caused by chlorine. This is an excellent treatment method.

Claims (1)

[Claims] (1) In a water treatment plant equipped with an activated carbon filtration basin, no chlorine is added in front of the activated carbon filtration basin, and activated carbon filtration adsorbs and removes most of water-soluble organic matter, odors, iron, manganese, and ammonia nitrogen. A water purification treatment method characterized in that chlorine is added after treatment, and then iron removal and manganese removal equipment is installed for treatment.