CN101701025A - A method for extracting humic acid from concentrated landfill leachate and treating wastewater - Google Patents

Abstract

The invention discloses a method for extracting humus acid from concentrated waste percolate and treating waste water, comprising the steps of adding coagulant into the concentrated waste percolate, stirring uniformly, adding coagulating agent, settling for 40 to 6 min, subsiding, separating to obtain supernatant, adjusting the PH value of supernatant to be 1.0 to 3;.0, settling for 4.0 to 8.0 h, subsiding, separating, concentrating the sediment to acquire high-concentrated liquid humus acid, and discharging after treating with advanced oxidization technique, wherein the coagulant is polymeric aluminum sulfate, polymeric ferric sulfate or polymeric ferric chloride and the coagulating agent is polyacrylamide. Treating the waste water with the method, the overall removing rates of COD and TOC are respectively above 96% and 97%, and the separated humus acid is semi-solid content which can be used as organic fertilizer to realize the comprehensive use of concentrated waste percolate and the treating target of treating pollution and changing waste into valuable.

Description

A method for extracting humic acid from concentrated landfill leachate and treating wastewater

technical field

The invention relates to an environment-friendly comprehensive treatment method for recycling humic acid from concentrated landfill leachate treated by a reverse osmosis membrane.

Background technique

At present, most of the urban waste in my country is disposed of by landfill, which will produce a large amount of landfill leachate. Landfill leachate is a liquid containing high-quality suspended solids and high-quality organic or inorganic components, which contains a considerable amount of toxic substances with high mass concentrations, and is completely discharged into rivers and lakes without treatment. The organic pollution in it Chemicals and inorganic pollutants will pollute aquatic organisms and crops, and cause harm to human health through the food chain and the ecological environment.

The water quality composition and concentration of landfill leachate change with the extension of the landfill period. Generally, the pH value of the landfill leachate in the later stage is close to neutral, and the alkalinity is high; the five-day biochemical oxygen demand (BOD ₅ ), chemical oxygen demand (COD _Cr ), volatile fatty acid (VFA) concentration and BOD ₅ /COD _Cr were low, and the biodegradability was poor; the metal ion concentration decreased, but the humic acid content and ammonia nitrogen concentration were high. Although countries have carried out research in this area for quite a long time, there is no practical and effective treatment method so far, especially for the treatment of leachate from landfills (landfills used for more than 10 years), which has always been a worldwide problem. problem.

Due to the high concentration of NH ₃ -N has an inhibitory effect on microorganisms, and the leachate contains a variety of toxic and harmful refractory substances (such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, etc.) and anti-biodegradable substances (such as humic acid , surfactants, etc.), the application of biological methods has been significantly restricted and the landfill leachate cannot be discharged up to the standard. Therefore, the use of physical and chemical methods, especially reverse osmosis technology, to treat landfill leachate is gradually becoming a trend. Compared with other treatment processes, the reverse osmosis membrane separation process can be carried out at room temperature, has no phase change, low energy consumption, can effectively remove inorganic salts and organic small molecule impurities, has a high water reuse rate, and can ensure good Treatment effect. At present, there are large-scale landfills in China that use reverse osmosis technology to treat leachate. However, reverse osmosis is only a separation process, and reverse osmosis membrane technology will inevitably produce concentrated liquid when treating landfill leachate. further processing. The reverse osmosis concentrate of leachate is a high-concentration organic waste liquid, and its COD and conductivity values are often 3 to 4 times, or even 5 times that of the original leachate, so there are a large number of concentrates containing high concentrations of humic acid Needs to be disposed of properly. The treatment of the concentrated solution mainly includes incineration, solidification, distillation and drying, and refilling, but such treatment has serious problems such as large power consumption and energy waste.

Contents of the invention

The purpose of the present invention is to provide a comprehensive utilization method for extracting humic acid (humic substances, HS) from the concentrated landfill leachate produced after reverse osmosis treatment and performing advanced treatment on it, so as to achieve the goals of pollution control and turning waste into treasure , so that the total removal rate of COD and TOC reaches 96.4% and 97.8%, respectively.

The object of the present invention can be achieved by the following measures:

A method for extracting humic acid from concentrated landfill leachate and treating waste water, comprising the steps of:

(1) Add coagulant to the concentrated landfill leachate, stir evenly, add coagulation aid, stir slowly for 1min, settle for 40-60min; 0.15% to 0.35% and 0.005% to 0.01%; the coagulant is polyaluminum sulfate, polyferric sulfate or polyferric chloride; the coagulation aid is polyacrylamide;

(2) Precipitation and separation to obtain a supernatant;

(3) Adjust the pH value of the supernatant to 1.0-3.0;

(4) Sediment for 4.0-8.0 hours, precipitate and separate; concentrate the precipitate to obtain high-concentration liquid humic acid;

(5) The supernatant obtained by precipitation and separation is discharged up to standard after being treated with advanced oxidation technology; the advanced oxidation technology is to add an oxidant and a catalyst in a catalytic reactor with sunlight as a light source, and the oxidation degradation time of the supernatant is 20 -30h; the oxidizing agent is hydrogen peroxide, and the catalyst is ferrous sulfate.

To further realize the object of the present invention, the separation mode of step (2) and step (4) is centrifugal separation.

The adjustment of step (3) pH is to adjust with sulfuric acid or hydrochloric acid.

The present invention has such advantages and beneficial effects as follows:

1. Due to the comprehensive treatment of landfill leachate, the total removal rates of COD and TOC have reached 96.4% and 97.8% respectively, achieving the purpose of treating waste water without causing secondary pollution.

2. The invention has the advantages of simple process, less equipment, and small investment, and is suitable for in-field treatment of garbage concentrates.

3. The method for extracting humic acid from the concentrated landfill leachate produced after reverse osmosis treatment has certain economic, social and environmental benefits. Humic acid can be applied to liquid organic fertilizers to realize resource utilization.

The method treats waste water, and the total removal rate of COD and TOC reaches more than 96% and 97% respectively, and the separated humic acid semi-solid can be used as organic fertilizer, thereby realizing the comprehensive utilization of concentrated landfill leachate, reaching Governance goals of pollution control and turning harm into wealth. Moreover, the process is simple, the equipment is less, the investment is small, while the three wastes are treated, the resources are comprehensively utilized, and there is no secondary discharge of the three wastes. The method of the invention overcomes the problem of large energy consumption in the technique of extracting humic acid from leachate membrane treatment concentrate, and has good social and economic benefits.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and examples, but the protection scope of the present invention is not limited to the scope indicated by the examples.

Example 1:

(1) Detect the concentrated landfill leachate treated by a reverse osmosis membrane, its TOC and COD are 2584mg/L and 4285mg/L respectively; put 1L of the concentrated landfill leachate into a 2.5L beaker, stir at room temperature, and add 0.15g of polyferric sulfate coagulant, 200-300r/min rapid stirring for 2min, add 1ml 0.05% (weight concentration) coagulation aid polyacrylamide, 200-300r/min rapid stirring for 2min, slow stirring for 1min, settling for 60min ; Centrifuge at 4000r/min for 15min. The measured supernatant TOC and COD were 2196mg/L and 3513mg/L, and the removal rates reached 15% and 18%, respectively.

(2) Add hydrochloric acid to the supernatant of step (1), adjust the pH to 1.5, settle for 4.0 hours, centrifuge at 4000r/min for 15 minutes, concentrate to semi-solid in a vacuum oven at 50°C, and obtain high-concentration liquid humic acid 6.5g. As determined by the potassium dichromate oxidation method, its content is higher than 90%. After testing, the supernatant TOC and COD were 1493mg/L and 2213mg/L respectively, and the removal rates reached 33% and 37% respectively.

(3) Use hydrochloric acid to adjust the pH of the supernatant in step (2) to 4.0, stir and add 2.5 g of ferrous sulfate at room temperature, divide it into 3 times, add 6 mL of hydrogen peroxide (30wt% H ₂ O ₂ ) every 10 min, and continue stirring for 30 min , let stand for 24 hours. After testing, TOC and COD were 92mg/L and 96mg/L respectively, and the removal rates reached 93.8% and 95.7%, respectively. It has reached the first-level standard of "Integrated Wastewater Discharge Standard" (GB8978-1996). The addition of oxidants in batches and the interval of dosing time determine the removal rate, which is also an advantage of the present invention. A better removal effect can be achieved with a lower dosage of oxidant.

Example 2:

(1) Detect the concentrated landfill leachate treated by a reverse osmosis membrane, its TOC and COD are 2584mg/L and 4285mg/L respectively; put 1L of the waste concentrate into a 2.5L beaker, stir at room temperature, and add 0.25 g of polyaluminum sulfate coagulant (percentage by weight), 200-300r/min rapid stirring for 2min, add 2ml 0.05% coagulation aid polyacrylamide, 200-300r/min rapid stirring for 2min, slow stirring for 1min, settling for 60min ; Centrifuge at 4000r/min for 15min. The measured supernatant TOC and COD were 2158mg/L and 3492mg/L, and the removal rates reached 16.5% and 18.5%, respectively.

(2) Add hydrochloric acid to the supernatant of step (1), adjust the pH to 3.0, settle for 6.0 hours, centrifuge at 4000r/min for 15 minutes, concentrate to semi-solid in a vacuum oven at 50°C, and obtain high-concentration liquid humic acid 6.2g. As determined by the potassium dichromate oxidation method, its content is higher than 90%. After testing, the supernatant TOC and COD were 1403mg/L and 2158mg/L, respectively, and the removal rates reached 35% and 38.2%, respectively.

(3) Adjust the pH of the supernatant in step (2) to 4.0 with hydrochloric acid, add 2.5 g of ferrous sulfate with stirring at room temperature, add 6 mL of hydrogen peroxide (30% H ₂ O ₂ ) in 3 times every 10 min, and continue stirring for 30 min. Stand still for 20h. After testing, TOC and COD were 96.8mg/L and 84mg/L respectively, and the removal rates reached 93.1% and 96.1% respectively. It has reached the first-level standard of "Integrated Wastewater Discharge Standard" (GB8978-1996). The addition of oxidants in batches and the interval of dosing time determine the removal rate, which is also an advantage of the present invention. A better removal effect can be achieved with a lower dosage of oxidant.

Example 3:

(1) Detect the concentrated landfill leachate treated by a reverse osmosis membrane. The TOC and COD are 2584mg/L and 4285mg/L respectively. Put 1L of the concentrated landfill into a 2.5L beaker, stir at room temperature, and add 0.35 g of polyferric sulfate coagulant (by weight percentage), 200-300r/min rapid stirring for 2min, add 2ml 0.05% coagulation aid polyacrylamide, 200-300r/min rapid stirring for 2min, slow stirring for 1min, settling for 60min ; Centrifuge at 4000r/min for 15min. The measured supernatant TOC and COD were 2106mg/L and 3424mg/L, and the removal rates reached 18.5% and 20.1%, respectively.

(2) Add sulfuric acid to the supernatant of step (1), adjust the pH to 1.0, settle for 8.0 hours, centrifuge at 4000r/min for 15 minutes, concentrate in a vacuum oven at 50°C to semi-solid, and obtain high-concentration liquid humic acid 10.3g. As determined by the potassium dichromate oxidation method, its content is higher than 90%. After testing, the supernatant TOC and COD were 1305mg/L and 2048mg/L, respectively, and the removal rates reached 38% and 40.2%, respectively.

(3) Use sulfuric acid to adjust the pH of the supernatant in step (2) to 4.0, add 2.5 g of ferrous sulfate with stirring at room temperature, add 6 mL of hydrogen peroxide (30% H ₂ O ₂ ) in 3 times every 10 min, and continue stirring for 30 min. Let stand for 24 hours. After testing, TOC and COD were 83.5mg/L and 71mg/L respectively, and the removal rates reached 93.6% and 96.5% respectively. It has reached the first-level standard of "Integrated Wastewater Discharge Standard" (GB8978-1996). The addition of oxidants in batches and the interval of dosing time determine the removal rate, which is also an advantage of the present invention. A better removal effect can be achieved with a lower dosage of oxidant.

Example 4

(1) Detect the concentrated landfill leachate treated by a reverse osmosis membrane. The TOC and COD are 2584mg/L and 4285mg/L respectively. Put 1L of the concentrated landfill into a 2.5L beaker, stir at room temperature, and add 0.35 g of polyaluminum sulfate coagulant (by weight percentage), 200-300r/min rapid stirring for 2min, add 1ml 0.05% coagulation aid polyacrylamide, 200-300r/min rapid stirring for 2min, slow stirring for 1min, settling for 60min ; Centrifuge at 4000r/min for 15min. The measured supernatant TOC and COD were 2126mg/L and 3509mg/L, and the removal rates reached 17.7% and 18.1%, respectively.

(2) Add sulfuric acid to the supernatant of step (1), adjust the pH to 1.5, settle for 8.0 hours, centrifuge at 4000r/min for 15 minutes, concentrate to semi-solid in a vacuum oven at 50°C, and obtain high-concentration liquid humic acid 10.5g. As determined by the potassium dichromate oxidation method, its content is higher than 90%. After testing, the supernatant TOC and COD were 1275mg/L and 2028mg/L respectively, and the removal rates reached 40% and 42.2% respectively.

(3) Use sulfuric acid to adjust the pH of the supernatant in step (2) to 4.0, add 2.5 g of ferrous sulfate with stirring at room temperature, add 6 mL of hydrogen peroxide (30% H ₂ O ₂ ) in 3 times every 10 min, and continue stirring for 30 min. Let stand for 24 hours. After testing, TOC and COD were 84mg/L and 69mg/L respectively, and the removal rates reached 93.4% and 96.6% respectively. It has reached the first-level standard of "Integrated Wastewater Discharge Standard" (GB8978-1996). The addition of oxidants in batches and the interval of dosing time determine the removal rate, which is also an advantage of the present invention. A better removal effect can be achieved with a lower dosage of oxidant.

Example 5

(1) Detect the concentrated landfill leachate treated by a reverse osmosis membrane. The TOC and COD are 2584mg/L and 4285mg/L respectively. Put 1L of the concentrated landfill into a 2.5L beaker, stir at room temperature, and add 0.25 g of polyferric chloride coagulant (by weight percentage), 200-300r/min rapid stirring 2min, add 1ml 0.05% coagulation aid polyacrylamide, 200-300r/min rapid stirring 2min, slow stirring 1min, sedimentation 60min; centrifuge at 4000r/min for 15min. The measured supernatant TOC and COD were 2139mg/L and 3514mg/L, and the removal rates reached 17.2% and 18.0%, respectively.

(2) Add nitric acid to the supernatant of step (1), adjust the pH to 2.0, settle for 4.0 hours, centrifuge at 4000r/min for 15 minutes, concentrate in a vacuum oven at 50°C to semi-solid, and obtain high-concentration liquid humic acid 5.5g. As determined by the potassium dichromate oxidation method, its content is higher than 90%. After testing, the supernatant TOC and COD were 1347mg/L and 2136mg/L, and the removal rates reached 37% and 39.2%, respectively.

(3) Use nitric acid to adjust the pH of the supernatant in step (2) to 4.0, add 2.5 g of ferrous sulfate with stirring at room temperature, add 6 mL of hydrogen peroxide (30% H ₂ O ₂ ) in 3 times every 10 min, and continue stirring for 30 min. Let stand for 30h. After testing, TOC and COD were 66mg/L and 51mg/L respectively, and the removal rates reached 95.1% and 97.6% respectively. It has reached the first-level standard of "Integrated Wastewater Discharge Standard" (GB8978-1996). The addition of oxidants in batches and the interval of dosing time determine the removal rate, which is also an advantage of the present invention. A better removal effect can be achieved with a lower dosage of oxidant.

Claims (3)

1. one kind is extracted humic acid and administers method for waste water from concentrated waste percolate, it is characterized in that comprising the steps:

(1) add coagulating agent at concentrated waste percolate, stir, add the coagulation auxiliary agent, after the stirring, sedimentation 40～60min; The add-on of coagulating agent and coagulation auxiliary agent be respectively percolate quality 0.15%～0.35% and 0.005%～0.01%; Described coagulating agent is polyaluminium sulfate, bodied ferric sulfate or poly-ferric chloride; Described coagulation auxiliary agent is a polyacrylamide;

(2) precipitation, separation get supernatant liquor;

(3) supernatant liquor is regulated pH value to 1.0～3.0;

(4) sedimentation 4.0～8.0h, precipitation, separation; The concentrating and precipitating thing promptly gets the liquid humic acid of high density;

(5) precipitating, separate the supernatant liquor that obtains uses high-level oxidation technology to handle the back qualified discharge; Described high-level oxidation technology is to be in the catalyticreactor of light source with daylight, adds oxygenant and catalyzer, and the supernatant liquor oxidative degradation time is 20-30h; Described oxygenant is a hydrogen peroxide, and described catalyzer is a ferrous sulfate.

2. according to claim 1ly extract humic acid and administer method for waste water from concentrated waste percolate, it is characterized in that: the separate mode of step (2) and step (4) is centrifugation.

3. according to claim 1ly extract humic acid and administer method for waste water from concentrated waste percolate, it is characterized in that: the adjusting of step (3) pH is to regulate with sulfuric acid or hydrochloric acid.