CN1508077A

CN1508077A - Method for treating waste water containing non-ionic surface active agent

Info

Publication number: CN1508077A
Application number: CNA021565090A
Authority: CN
Inventors: 程学文; 胡家祥; 栾金义; 王文军; 杜蓓; 王宜军
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2002-12-16
Filing date: 2002-12-16
Publication date: 2004-06-30
Anticipated expiration: 2022-12-16
Also published as: CN1212981C

Abstract

The present invention provides a treatment method of non-ionogenic surface-active agent (NIS) waste water, relates to the field of organic chemical waste water treatment technology. Said method uses iron filings microelectrolysis treatment as core, after the pH of NIS waste water is regulated to proper value, said NIS waste water can be fed into microelectrolytic reactor to make iron filings microelectrolysis treatment, then the treated waste water is fed into precipitation tank so as to remove Fe(2+) and Fe(3+) introduced in the course of making microelectrolysis. After having been treated by said method the removing rate of NIS in NIS waste water can be up to 80%.

Description

Method for treating wastewater containing nonionic surfactant

Technical Field

The invention relates to a method for treating organic chemical wastewater, in particular to a method for treating wastewater containing a nonionic surfactant (NIS).

Background

Nonionic surfactants (NIS) are surfactants which are used in large amounts following anionic surfactants and are also important. The nonionic surfactant has high surface activity, low surface tension of an aqueous solution of the nonionic surfactant, and lower critical micelle concentration than that of the ionic surfactant, so that the nonionic surfactant has good emulsifying capacity and washing effect. In recent years, the yield of the nonionic surfactant in China is greatly increased. At present, polyoxyethylene type and polyalcohol type surfactants are mainly used, and the surfactants belong to substances which are difficult to degrade biologically.

With the increasing use amount of NIS, a large amount of NIS enters a water body (such as chemical wastewater, printing and dyeing wastewater and the like) through various ways, so that COD in the water is increased and a large amount of stable foam is generated, thereby inhibiting the degradation of toxic substances. The large amount of foam also makes the sludge in the wastewater difficult to settle down, thereby affecting the treatment efficiency of the wastewater purification equipment.

There are no environmental quality standards and emission standards for NIS, but it is necessary to develop effective treatment techniques in view of their adverse environmental impact. Due to the special properties of NIS, the treatment effects of common wastewater treatment methods such as coagulation and biochemistry are not ideal; although the purpose of separating the NIS from the water can be achieved by adopting physical methods such as foam separation and the like, the structure of the NIS is not damaged, the treatment is not thorough, and the cost of treating the concentrated phase after the foam separation is still high; advanced oxidation methods such as wet oxidation can thoroughly destroy the structure of NIS and eliminate the toxic action of NIS, but the treatment cost is quite expensive, and the popularization and the application have certain difficulty. Thus, it is of great importance to develop an economical and efficient treatment method for NIS wastewater.

Iron filings microelectrolysis is an electrochemical oxidation method. Iron filings (mainly iron carbon alloys) form a large number of small galvanic cells in an electrolyte solution, with iron as the anode and carbon as the cathode. The electrode reaction is as follows:

anode:

cathode: (acid condition)

(alkaline, neutral conditions)

In the electrode reaction, the intermediate product and the final product have high chemical activity, can react with a plurality of pollutants contained in water, and eliminate the toxicity through chemical reaction.

Chinese patent CN-1078959A mentions the research of applying an iron-carbon flocculation bed device to kitchen sewage. The invention designs an iron-carbon flocculation bed which is internally filled with carbon-containing iron chips and loose material particles and can solve the problem that the iron-carbon bed is easy to harden. The invention mainly aims at kitchen sewage, and organic components in the kitchen sewage are very complex and mainly comprise animal and vegetable oil, protein, starch, ionic surfactant and the like. The removal of NIS from NIS wastewater by this method is not suitable because it is believed that the treatment effect is significant only if a large amount of air must be introduced to supplement oxygen during the treatment process to enhance contact. When air is introduced into the NIS wastewater, a large amount of foam is generated, the operation is difficult to control, and the treatment effect is not improved by supplementing oxygen.

In addition, JP-10-128096A and JP-2001-96279A, and Chinese CN-1179488A, CN-1240768A, CN-1040016A and CN-1068799A all adopt the micro-electrolysis treatment of iron filings, and are only limited to the research of electroplating and printing and dyeing wastewater.

In view of the current research situation at home and abroad, no literature report on the NIS wastewater treatment method is available. Meanwhile, according to the previous analysis, the existing scrap iron micro-electrolysis treatment technology is directly applied to the treatment of NIS wastewater and has some problems. Therefore, there is a need to develop an economically feasible technique to achieve efficient treatment of NIS wastewater.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a novel method for treating wastewater containing a nonionic surfactant (NIS), which has the advantages of high treatment efficiency, high reaction speed, simple and convenient operation and the like while meeting the treatment requirement and is easy to realize industrial application.

The invention adopts an iron scrap micro-electrolysis method to treat the wastewater containing the nonionic surfactant (NIS), and specifically comprises the following steps:

a. adjusting the pH of the wastewater containing the nonionic surfactant to 0.5-3.5 in an adjusting tank;

b. after the pH value of the wastewater is adjusted, the wastewater enters a micro-electrolysis reactor, the wastewater stays for 10-60 min, and cast iron scraps with the granularity of 20-100 meshes are filled in the micro-electrolysis reactor;

c. the wastewater treated by the micro-electrolysis reactor enters a precipitation tank, and alkali liquor is added into the precipitation tank to remove Fe generated in the micro-electrolysis treatment process of the scrap iron²⁺And Fe³⁺And controlling the pH value of the treated wastewater discharged from the precipitation tank to be 7.0-9.0.

The pH of the NIS-containing wastewater is generally around 7. In the treatment method, the pH value of the wastewater containing NIS during the micro-electrolysis reaction is controlled to be 0.5-3.5. When the pH value is lower, the micro-electrolysis treatment effect is better. However, the pH is too low, and the amount of acid consumed is large. Therefore, the pH value of the wastewater is required to be selected properly, and the pH value of the wastewater is adjusted to be 0.5-3.5, preferably 1.0-3.0.

The research of the invention shows that the finer the granularity of the cast iron chips filled in the micro-electrolysis reactor, the better the treatment effect, but the too fine iron chips are easy to run off and the resistance of the iron chip bed layer is increased. Therefore, the particle size of the scrap iron in the micro-electrolysis reactor is kept between 20 and 100 meshes, preferably between 30 and 90 meshes. Thescrap iron is generally selected from cast iron scrap and comprises an iron-carbon alloy.

In the treatment method, the retention time of the wastewater containing NIS in the micro-electrolysis reactor is controlled within 10-60 min. When the NIS-containing wastewater is treated by the scrap iron micro-electrolysis method, the removal rate of NIS is obviously increased along with the extension of the retention time, but the treatment efficiency is slowly increased after the retention time exceeds 10min, and the treatment effect is basically stable after the retention time exceeds 60 min. Therefore, the retention time of the NIS wastewater is recommended to be 10-60 min, preferably 20-50 min.

The pH of the effluent of the NIS-containing wastewater after the wastewater is precipitated by the precipitation tank is controlled to be 7.0-9.0. Because the invention mainly aims at the treatment of the NIS which is difficult to be biodegraded, a biochemical treatment device is required to be added later. Because a certain amount of ferric ions and ferrous ions can be introduced into NIS wastewater after iron scrap micro-electrolysis treatment, and the ferric ions and the ferrous ions can generate adverse effects on subsequent biochemical treatment, alkali liquor (generally 10% sodium hydroxide solution) needs to be added into a precipitation tank to remove the ferric ions and the ferrous ions, and the pH of effluent is controlled to be 7.0-9.0, preferably 7.5-8.5.

And discharging the wastewater treated by the scrap iron micro-electrolysis method out of the precipitation tank, and then discharging the wastewater into a subsequent biochemical treatment system for biochemical treatment. The biochemical treatment is carried out by a usual biochemical treatment method such as an activated sludge method, a contact oxidation method or the like. The sediment and the like are accumulated to a certain amount and then are treated in a centralized way, such as landfill, incineration and the like.

The invention adopts the scrap iron micro-electrolysis method as the basic method for treating the non-ionic surfactant (NIS) wastewater, so that the NIS in the wastewater can be effectively removed through simpler steps. The method has the advantages of stable and reliable treatment effect, simple and easy operation, high treatment efficiency, low requirement on equipment, low cost and easy realization of industrial application.

The removal rate of NIS in the wastewater can reach 80.0 percent by the treatment of the method, which is beneficial to the smooth proceeding of the subsequent biochemical treatment. Through the treatment of scrap iron micro-electrolysis method and subsequent biochemical treatment, etc., the wastewater containing the nonionic surfactant can reach the discharge standard

Drawings

FIG. 1 is a process flow chart of scrap iron micro-electrolysis treatment of nonionic surfactant (NIS) wastewater

The detailed process of the present invention is described below with reference to fig. 1:

because the pH of the NIS-containing wastewater can influence the treatment effect of iron scrap micro-electrolysis, and when the pH is lower, the treatment effect is better, the pH of the NIS wastewater needs to be adjusted to 0.5-3.5, preferably 1.0-3.0. The pH of the wastewater can be adjusted by using common acid, such as sulfuric acid or phosphoric acid. After adjusting the pH value of the NIS wastewater to a proper value, the NIS wastewater can enter a micro-electrolysis reactor to carry out scrap iron micro-electrolysis treatment. The used micro-electrolysis reactor is a general micro-electrolysis reactor which is generally in a cylindrical structure, and cast iron scraps are filled in the micro-electrolysis reactor. The main component of the cast iron scraps is iron-carbon alloy, and the granularity is required to be 20-100 meshes, preferably 30-90 meshes. The wastewater can enter the precipitation tank after staying in the micro-electrolysis reactor for a period of time, the treatment effect is improved along with the extension of the residence time of the wastewater, but the treatment effect is improved after the residence time exceeds 10min, and the treatment effect is basically stable after the residence time slowly exceeds 60min, so that the residence time of the NIS wastewater needs to be controlled within 10-60 min, preferably 20-50 min. The purpose of setting up the precipitation tank is mainly to get rid of iron ion and ferrous ion that iron fillings microelectrolysis in-process produced. Because the invention mainly aims at the NIS treatment in the wastewater, the biochemical treatment part is added to realize the standard discharge of the wastewater, and the existence of ferric ions and ferrous ions can generate adverse effect on the biochemical treatment, so the removal is needed. Adding alkali liquor into the precipitation tank, and controlling the pH of the effluent of the precipitation tank to be 7.0-9.0, preferably 7.5-8.5. And the wastewater treated by the micro-electrolysis method enters a biochemical treatment system for biochemical treatment. The biochemical treatment system can adopt an activated sludge method or a contact oxidation method.

Detailed Description

Example 1

Taking a proper amount of NIS wastewater (the pH of raw water is 7.0), adjusting the pH to 3.5 (the pH is adjusted by 98% concentrated sulfuric acid), then feeding the NIS wastewater into an iron scrap micro-electrolysis reactor, and filling iron scraps (sold in markets) with the particle size distribution of 20-100 meshes in a column, wherein the main component of the iron scraps is iron-carbon alloy. Treating wastewater in the iron scrap micro-electrolysis column for 10min, feeding into a precipitation tank, adding a certain amount of alkali solution (10% NaOH solution) into the tank to remove Fe²⁺And Fe³⁺And controlling the pH value of the effluent to be 7.0.

Through the micro-electrolysis treatment of the scrap iron, the removal rate of NIS in the wastewater is 82 percent.

Example 2

Taking a proper amount of NIS wastewater (the pH of raw water is 7.0), adjusting the pH to 0.5 (the pH is adjusted by 98% concentrated sulfuric acid), then feeding the NIS wastewater into an iron scrap micro-electrolysis reactor, and filling iron scraps (sold in markets) with the particle size distribution of 20-100 meshes in a column, wherein the main component is iron-carbon alloy. Allowing the wastewater to stay in the iron scrap micro-electrolysis column for 60min, introducing into a precipitation tank, adding a certain amount of alkali solution (10% NaOH solution) to remove Fe²⁺And Fe³⁺And controlling the pH value of the effluent to be 9.0.

The removal rate of NIS in the wastewater is 99.5 percent through scrap iron micro-electrolysis treatment.

Comparative example 1

Taking a proper amount of NIS wastewater (the pH of raw water is 7.0), adjusting the pH to 3.5 (the pH is adjusted by 98% concentrated sulfuric acid), then feeding the wastewater into an iron scrap micro-electrolysis reactor, and filling cast iron scraps (sold in markets) with the particle size distribution of 20-100 meshes into a column, wherein the main component is iron-carbon alloy. The wastewater stays in the scrap iron micro-electrolysis column for 6min and then enters a precipitation tank,adding a certain amount of alkali liquor (10% NaOH solution) into the tank to remove Fe²⁺And Fe³⁺And controlling the pH value of the effluent to be 9.0.

Through the micro-electrolysis treatment of the scrap iron, the removal rate of NIS in the wastewater is 55 percent, and the expected treatment effect of 80 percent is not achieved.

Comparative example 2

Taking a proper amount of NIS wastewater (the pH of raw water is 7.0), directly feeding the NIS wastewater into an iron scrap micro-electrolysis reactor without adjusting the pH, and filling iron scraps (sold in markets) with the particle size distribution of 20-100 meshes into a column, wherein the main component is iron-carbon alloy. Allowing the wastewater to stay in the iron scrap micro-electrolysis column for 60min, introducing into a precipitation tank, adding a certain amount of alkali solution (10% NaOH solution) to remove Fe²⁺And Fe³⁺The effluent pH was 9.0.

The removal rate of NIS in the wastewater is 20.5 percent through scrap iron micro-electrolysis treatment.

Thus, it is known that the treatment effect is not satisfactory if the NIS wastewater is directly treated without adjusting the pH.

Claims

1. A method for treating wastewater containing nonionic surfactant comprises the following steps:

b. after the pH value of the wastewater is adjusted, the wastewater enters a micro-electrolysis reactor, the wastewater stays for 10-60 min, and cast iron scraps with the granularity of 20-100meshes are filled in the micro-electrolysis reactor;

c. the wastewater treated by the micro-electrolysis reactor enters a precipitation tank, alkali liquor is added into the precipitation tank,

c. controlling the pH value of the treated wastewater discharged from the precipitation tank to be 7.0-9.0.

2. The method for treating waste water according to claim 1, wherein the pH of the waste water containing the nonionic surfactant is adjusted to 1.0 to 3.0 in the adjusting tank.

3. The wastewater treatment method according to claim 1, wherein the particle size of the iron pieces in the micro-electrolysis reactor is 30-90 meshes.

4. The method for treating wastewater according to claim 1, wherein the residence time of wastewater in the micro-electrolyzer is controlled to be 20 to 50 min.

5. The method for treating wastewater according to claim 1, wherein the pH of the treated wastewater discharged from the precipitation tank is 7.5 to 8.5.