KR20000063167A - A process for the purification of factory wastes of pigments containing rich nitrogen element - Google Patents

Abstract

PURPOSE: A treatment system for pigment wastewater is provided, which is characterized in that the system treats efficiently wastewater containing large quantities of nitrogen by using chlorine gas. CONSTITUTION: A treatment system for pigment wastewater is composed of four steps such as follows: (i) a first treatment step neutralizing pigment wastewater containing large quantities of nitrogen by using acid and alkali and removing sludge by using flocculation and compressed-air flotation; (ii) a second treatment step settling Cu ion by injecting settling agents and coagulants; (iii) a third treatment step treating the wastewater in an aerobic reactor by using activated sludge; and (iv) a forth treatment step withdrawing nitrogen gas by adding chlorine gas and neutralizing and oxidizing finally organic matter.

Description

A method for efficiently purifying pigment wastewater containing a large amount of nitrogen {A PROCESS FOR THE PURIFICATION OF FACTORY WASTES OF PIGMENTS CONTAINING RICH NITROGEN ELEMENT}

The present invention relates to a method for efficiently purifying pigment wastewater containing a large amount of nitrogen, particularly a method for efficiently removing nitrogen in wastewater using chlorine gas.

In recent years, due to environmental problems, the treatment regulations for pigment wastewater have become more strict, and wastewater treatment problems play an important role in pigment production because the treatment cost of wastewater accounts for 30-40% of the total production cost.

Conventional processes for treating pigment wastewater include acid alkali treatment and flocculation of the wastewater, followed by physical pretreatment, secondary chemical treatment with various organic and inorganic flocculants, and aeration with activated sludge for biological treatment. It is common.

However, if the existing activated sludge method is used for the treatment of pigment wastewater containing a large amount of nitrogen components such as ammonia and ammonium, the nitric oxide becomes more than the allowable standard of environmental regulations, and the activated sludge process is repeated to remove it below the standard. Wastewater treatment costs are very high because they have to run for a long time in a large-scale facility for performing or activated sludge process.

The present invention has been made to solve the above-mentioned problems, and the nitrogen sludge treatment step is performed after the first step of the active sludge treatment step to purify the pigment wastewater containing a large amount of nitrogen at low cost, and the purification efficiency of the activated sludge treatment method. Provide a waste water purification method that is equivalent to or even higher.

1 is a flow chart of a wastewater purification process according to the present invention.

The present invention relates to a method for efficiently purifying a pigment wastewater containing a large amount of nitrogen, comprising: (i) a first treatment step of treating the pigment wastewater with an acid and an alkali, flocculating and pressure-lifting to remove sludge; (ii) a secondary treatment step of injecting, precipitating and flocculating a precipitant for precipitating copper ions and a flocculant to remove monovalent copper ions (Cu ⁺ ); (iii) a third treatment step of performing activated sludge treatment in a microbial aeration tank; And (iv) injecting chlorine gas to degas the nitrogen and finally oxidize and neutralize the organics.

The wastewater purification process according to the present invention is more clearly understood with reference to FIG. 1.

The primary treatment step is to reduce the load on the secondary chemical treatment by neutralizing the wastewater with acid and alkali, injecting and coagulating inorganic and organic flocculants, and then flocculating to form sludge and removing it. Sulfuric acid is mainly used as a neutralizing acid, and sodium hydroxide is mainly used as an alkali. Using acids and alkalis, the pH of the wastewater is neutralized to 7.5-8.5, the proper pH for wastewater treatment.

After primary treatment, COD (chemical oxygen demand) is reduced by 60-70%, BOD (biological oxygen demand) is reduced by 5-20%, Cu ⁺ is 80-95%, SS (suspendable) 90-95% Removed.

Secondary treatment is a step to reduce the Cu + concentration which adversely affects the third treatment step biological treatment while reducing the COD of the first pretreated wastewater.

The copper ions in the wastewater once react with the precipitant to be precipitated and aggregated by the coagulant.

Sodium sulfide (Na ₂ S) is preferably used as a precipitant for precipitating Cu ⁺ ions, and ferric sulfate (Fe ₂ (SO ₄ ) ₃ ), ferric chloride (FeCl ₃ ), and acrylamide type are preferably used as the coagulant. Polymers are used.

Sodium sulfide is usually injected at a rate of 70 ppm per minute.

In a preferred embodiment, sodium sulfide (Na ₂ S) is used at a concentration of 540-580 ppm, ferric sulfate (Fe ₂ (SO ₄ ) ₃ ) at 450-550 ppm and acrylamide-based polymer at a concentration of 900-1100 ppm.

After secondary treatment, at least 95% of Cu ⁺ is removed, at least 75-80% at COD, 21-25% at BOD, and at least 98% for SS.

The tertiary treatment step is a biological treatment step, ie an activated sludge treatment step, the specific method of performing is well known. The secondary treated wastewater is preferably diluted with dilution water before aeration in the microbial aeration tank. The secondary precipitate is separated after aeration in a microbial aeration tank by known methods.

If the wastewater contains a large amount of nitrogen, the BOD and COD will be above environmental standards even after tertiary treatment. In order to purify wastewater below the environmental legislative standard using only the activated sludge method, there is a problem of investing vast installation space, installation cost and enormous operating cost in order to repeat the activated sludge process several times or install a large number of large tanks.

According to the present invention, after performing the existing activated sludge process primarily, a fourth treatment step is performed in which chlorine gas is subsequently injected to degas nitrogen and finally oxidize and neutralize organic matter.

The ammonium nitrogen (NH ₄ -N) or ammonia nitrogen (NH ₃ -N) component in the wastewater to be treated reacts with chlorine gas to generate nitrogen gas, and the organic matter is oxidized by chlorine.

This is expressed as a reaction scheme as follows.

Cl ₂ + H ₂ 0 ↔HOCl + HCl

2NH ₃ + 3HOCl ↔N ₂ + 3H ₂ 0 + 3HCl

Chlorine gas is injected at a rate of 5 kg / hour to a concentration of 170-190 ppm and held for 7-9 hours.

After nitrogen treatment, the neutralization process is preferably discharged using 33% sodium hydroxide solution and allowing the pH to be automatically adjusted to 4.6 to 8.5.

The present invention is described in detail by the following examples, which are merely exemplary and the spirit of the present invention is not limited thereto.

Example 1

After the wastewater stayed in the collecting tank for 2.5 days, the wastewater was transferred to a neutralization tank, neutralized and coagulated, and then transferred to a pressure flotation tank to pressurize and separate sludge. Then transferred to Cu ⁺ to remove the reaction _{vessel, Na 2 S 560 ppm, Fe} 2 (SO 4) 3 500 ppm, acrylamide-based polymer is such that a _{1000 ppm Na 2 S, Fe 2} (SO 4) 3 , and an acrylamide-based polymer Was injected for 1 hour, transferred to the primary precipitation bath, and precipitated for 9 hours to separate the primary precipitate. After transfer to the dilution tank, waste water: dilution water = 1: 2: dilute to 1 hour, stay for 1 hour, transfer to the microbial aeration tank, aeration for 1.6 days, transfer to the secondary settling tank and stay for 6 hours to maintain the secondary precipitate Separated. After transferring to the chlorine gas input tank, the chlorine gas was injected at a rate of 5 kg / hour until the concentration reached 185 ppm, and the chlorine gas was kept for 8 hours, transferred to a neutralization tank, neutralized with sodium hydroxide, and discharged.

Table 1 shows the results of measuring the COD, BOD, Cu ⁺ , and SS values at each step.

Table 1

COD BOD Cu ⁺ SS Concentration ppm % Reduction Concentration ppm % Reduction Concentration ppm % Reduction Concentration ppm % Reduction Wastewater 1500 2000 1300 1000 Primary treatment 350 76 2000 0 50 96 20 95 Secondary processing 258 81 2000 0 3 98.5 10 98 Tertiary treatment 250 83 30 98.5 <1 99.7 5 99 4th process 80 94.6 20 99 <1 99.7 5 99

As can be seen from the above table, even after the third treatment, each value was above the environmental limit value (COD 130ppm, BOD 120ppm, Cu ⁺ 3ppm, SS 130ppm), but after the fourth treatment each value was reduced to below the reference value.

Therefore, according to the present invention, it is possible to efficiently purify the pigment wastewater containing a large amount of nitrogen components.

Claims (4)

(i) a first treatment step of treating the pigment wastewater containing a large amount of nitrogen with an acid and an alkali, flocculating and flotation to remove sludge; (ii) a secondary treatment step of injecting, precipitating and flocculating a precipitant for precipitating copper ions and a flocculant to remove monovalent copper ions (Cu ⁺ ); (iii) a third treatment step of performing activated sludge treatment in a microbial aeration tank; And (iv) a fourth treatment step of degassing nitrogen by injecting chlorine gas and finally oxidizing the organics, neutralizing and discharging A method for efficiently purifying a pigment wastewater containing a large amount of nitrogen components. The method of claim 1 wherein chlorine gas is injected at a rate of 5 kg / hour. The method of claim 1 wherein the chlorine gas is injected until the concentration is 170-190 ppm. The method of claim 1 wherein the chlorine gas is retained for 7-9 hours.