CN103771679A

CN103771679A - Synergetic treatment method of energy-saving dehydration and efficient heavy metal removal of sewage and sludge

Info

Publication number: CN103771679A
Application number: CN201410006123.6A
Authority: CN
Inventors: 严密; 徐璋; 任建莉; 胡艳军; 平传娟; 钟英杰
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Zhejiang University of Technology ZJUT
Priority date: 2014-01-06
Filing date: 2014-01-06
Publication date: 2014-05-07
Anticipated expiration: 2034-01-06
Also published as: CN103771679B

Abstract

The invention provides a synergetic treatment method of energy-saving dehydration and efficient heavy metal removal of sewage and sludge. The method comprises the following steps: mechanical dehydrating crude sludge, adding composite additive which is 1-3 percent by mass of the dehydrated sludge into the sludge; uniformly mixing the sludge and the composite additive, and transferring the mixture into a hydrothermal reactor, reacting for 30-60 min at 150-180 DEG C under the pressure of 400-1,000kPa; cooling after the reaction is completed, filter-pressing and dehydrating by using a plate-and-frame filter press; regulating the pH value of the filter-pressed sludge to 5.5-10 by quicklime and discharging to the outside to serve as soil, or regulating the Ca/S molar ratio to 1.0-1.2 by adding quicklime and carrying out incineration treatment. According to urban domestic sewage and sludge treated by the method, the solid content can be increased, the concentration of heavy metal can be reduced, organic noxious substances can be reduced, applicability of sludge soil utilization can be improved, and emission of incineration treatment pollutants can be reduced.

Description

A kind of sewage sludge energy-saving dewatering and heavy metal efficiently remove cooperative processing method

(1) technical field

The present invention relates to a kind of sewage sludge energy-saving dewatering and heavy metal and efficiently remove cooperative processing method.

(2) background technology

Mud is the solid sediment producing in sewage treatment process, accounts for the 0.3%～0.5%(that processes the water yield take water content as 95%).The wet mud (85% water ratio) that China's year municipal sewage treatment produces can reach more than 3,000 ten thousand tons.In mud, contain a large amount of objectionable impuritiess, as heavy metal, organic pollutant (polycyclic aromatic hydrocarbons is with dioxin etc.), a large amount of sex pheromone etc., being easy to form " secondary pollution ", is a kind of solid waste that has a large capacity and a wide range and human body and environment are all had to very large damaging effect.In municipal sewage treatment process, sludge yield constantly increases, and how safe, economy is disposed and utilizes mud to become extremely urgent problem.The utilization of mud soil is mud fast processing and resource utilization method, is one sustainable disposal technology cheaply; Incineration disposal can be realized fast and harmless, minimizing and energy.But the bottleneck that the height of mud is moisture, characteristic that be rich in heavy metal and be all difficult to remove becomes recycling sludge utilization and harmlessness disposing, need to seek and explore a kind of low cost, eco-friendly sludge pre-treatment method.

Moisture has 4 kinds of existence forms in mud: free water, interstitial water, surface-bonded water and internal water.Free water can remove by mechanism filter-pressing method, but surface-bonded water and internal water can not be dewatered and be removed by mechanism filter-pressing, need carry out pre-treatment, improves the dewatering of mud, improves mechanical dehydration effect.The wet solution of mud hydro-thermal is the preconditioning technique of simple, efficient and less energy-consumption.After the wet solution of hydro-thermal, mud flco is dismissed, the fragmentation of microorganism cells body, and colloidal structure destroys, and ICW is released, and has improved settleability and the dewatering of mud.Relatively conventional heat drying, utilizes the wet solution lignin-sludge of hydro-thermal to avoid water vapor to absorb latent heat, greatly reduces energy consumption.But directly use active sludge to carry out the wet solution processing of hydro-thermal, still exist mud amount large, moisture percentage in sewage sludge is high, there is still larger deficiency of energy consumption.

By add chemical agent in mud, improve the redox potential (Eh) of mud or reduce sludge pH value, thereby Heavy Metals in Sludge is transformed to soluble ionic state or complexing ion state by the compound of soluble state, can effectively remove Heavy Metals in Sludge, i.e. chemical leaching method.It is good that chemical leaching method has removal effect, the advantage that the treatment time is short.The medicament using mainly contains the strong oxidizers such as complexing agent and hydrogen peroxide such as the various inorganic acids such as sulfuric acid and nitric acid, ethylenediamine tetraacetic acid (EDTA) (EDTA), nitrogen base nitrilotriacetic (NTA) and bicarbonate of ammonia.The use of various inorganic acids, highly basic can cause in waste water acid-basicity too high, and final sewage is difficult to dispose, and needs exploitation and uses the friendly type medicament of novel environmental.

(3) summary of the invention

The object of the invention is to provide a kind of sewage sludge energy-saving dewatering and heavy metal efficiently removes cooperative processing method.Its core is that hydrothermal method coupling chemical leaching method realizes and improves dewatering performance of sludge, efficiently removes heavy metal, degraded organic toxicant and sterilising effect.Through this mud after treatment, reduce moisture, reduce heavy metal content and leachability, improve suitability and security that mud soil utilizes, also reduce sludge incineration pollutant emission.

The technical solution used in the present invention is:

A kind of sewage sludge energy-saving dewatering and heavy metal efficiently remove cooperative processing method, described method comprises: first former raw sludge is 80%～85% through mechanical dehydration to water ratio, it is the composite additive of sludge quality 1%～3% after dehydration that mud after dehydration adds quality, and described composite additive is HEDTA(hydroxyethylethylene diamine tri-acetic acid), oxalic acid and NH ₄nO ₃the mixture of mass ratio 15～20:2:1; Mud and composite additive mix rear transfer and enter hydrothermal reaction kettle, are controlled under 150 ℃～180 ℃, 400kPa～1000kPa condition and react 30min～60min; Reaction finish rear cooling, with plate-and-frame filter press filter-press dehydration to water ratio under 1.5～3.0MPa be 30～40%; It is 5.5～10.0 outward transport soil utilizations that mud after press filtration regulates pH value with unslaked lime, or interpolation unslaked lime adjusting Ca/S mol ratio is 1.0～1.2 rear incineration disposals.

The wet solution of hydro-thermal is utilized the characteristics such as molecular motion under hydrothermal condition is accelerated, and it is large that ion-product constant becomes, and spread coefficient change is large, can strengthen removal effect.Hydrothermal method is also applied to the Some Organic Pollutants of degrading in the solid wastes such as flying dust, comprises that (PAHs) is with dioxin (PCDD/Fs) etc. have obtained research and checking to polycyclic aromatic hydrocarbons in flying dust disposal field.The wet solution technology of hydro-thermal is applied in can be optimized dewatering and realize sterilising effect on changing food waste, bacterium, under high temperature and high pressure environment, can be lost activity by elimination after maintaining certain hour.

Preferably, hydrothermal reaction kettle used is the hydrothermal reaction kettle of tool agitating function, and described hydro-thermal reaction is carried out under 150 ℃～160 ℃ of temperature, pressure 400kPa～600kPa, stir speed (S.S.) 100～200r/min condition.

Concrete, described former raw sludge is from municipal sewage plant.

According to the technological line of step dehydration of the present invention, first the former raw sludge in municipal sewage plant carries out one-time mechanical dehydration, and mud solid content can reach 15%～20%; Mud after mechanical dehydration maintains after 30～60min under (150 ℃～180 ℃) under hydrothermal condition, dewatering significantly improves, carry out filter press dehydration, mud cake solid content can reach 70% again, and water ratio meets the requirement of soil utilization and mud self-sustaining burning; For removing Heavy Metals in Sludge, in mud, add composite additive, the heavy metal of strengthening soluble state under hydrothermal condition becomes soluble state or complex state enters liquid phase, after secondary mechanical dehydration, removes, and reduces soil and utilizes heavy metals in process and incineration disposal process to discharge to pollute; Under sour water thermal environment, the bacterium in mud and organic nuisance obtain Partial digestion.

Improve solid content, reduced heavy metal concentration by the inventive method urban domestic sewage sludge after treatment, reduced organic nuisance, can improve suitability and the pollutant emission of reduction incineration disposal that mud soil utilizes.Its beneficial effect is mainly reflected in:

1. because using the wet solution technology of hydro-thermal, mud carries out mummification pre-treatment, in treating processes mud, moisture does not absorb steam latent heat, and the wet charging mud of separating tank of hydro-thermal has passed through one-time mechanical dehydration, so this energy saving technology effect is remarkable, relatively traditional drying technique can save energy 60%～70%;

2. can reach 70% through the mud solid content of Synergistic method processing, Lower heat value exceedes 10000kJ/kg, meets the requirement to water ratio of the utilization of mud soil and self-sustaining burning;

3. utilize composite additive that heavy metal is shifted and enters liquid phase from solid phase, reduce the content of Heavy Metals in Sludge by filter-press dehydration, effectively alleviated mud soil and utilized the heavy metal in process and incineration disposal to discharge pollution;

4. the wet solution process of hydro-thermal, in mud also there is partial oxidation decomposition and entered in water in dioxin and polycyclic aromatic hydrocarbons, reduced the content of organic nuisance in dewatered sludge;

5. in the method process, not using strong acid and strong base and harmful additive, is a kind of eco-friendly technology.

(4) accompanying drawing explanation

Fig. 1 is the process flow sheet of the inventive method.

(5) embodiment

Below in conjunction with specific embodiment, the present invention is described further, but protection scope of the present invention is not limited in this:

Embodiment 1:

Water ratio is 98.7% former raw sludge obtains water ratio 82% after belt filter press mechanical dehydration primary dewatering mud in Hangzhou Qi Ge sewage work, and gathering 10kg primary dewatering mud, to take back laboratory refrigeration for subsequent use; Get primary dewatering mud 100.0g, add 2.0g composite additive (HEDTA, oxalic acid and NH ₄nO ₃the mixture of mass ratio 17:2:1) be fully uniformly mixed, and mud is shifted and enters hydrothermal reaction kettle; Open agitator motor, rotating speed is 100r/min, then opens electrically heated (Practical Project can directly lead to saturation steam) and make hydrothermal reaction kettle temperature be elevated to 160 ℃, and pressure, at 450kPa, maintains 60min, stops also cooling reactor of electrically heated after the time meets; Stop agitator motor and take out mud after cooling Deng reactor, utilize experiment plate-and-frame filter press press filtration mud (3MPa), obtain 27.9g water ratio and be 36% second dehydration mud; In second dehydration mud, add 1.5g unslaked lime, it is 1.11 that moisture percentage in sewage sludge drops to 33.1%, Ca/S mol ratio.Also done not heavy metal concentration contrast experiment when heating cycle of adding composite additive and reactor, two groups of experiment Of Heavy Metal Level In Sludges and removal effect are as table 1 simultaneously.

Table 1: heavy metal content and decreasing ratio in dewatered sludge

Remarks: a, hydrothermal temperature is 160 ℃, but does not use composite additive; B, hydrothermal temperature is room temperature, has used composite additive.

From table 1, adopt cooperative processing method of the present invention, compared with independent hydrothermal treatment consists, heavy metal removing rate improves greatly.

Claims

1. a sewage sludge energy-saving dewatering and heavy metal efficiently remove cooperative processing method, described method comprises: first former raw sludge is 80%～85% through mechanical dehydration to water ratio, it is the composite additive of the sludge quality 1%～3% after dehydration that mud after dehydration adds quality, and described composite additive is HEDTA, oxalic acid and NH ₄nO ₃the mixture of mass ratio 15～20:2:1; Mud and composite additive mix rear transfer and enter hydrothermal reaction kettle, are controlled under 150 ℃～180 ℃, 400kPa～1000kPa condition and react 30min～60min; Reaction finish rear cooling, with plate-and-frame filter press filter-press dehydration to water ratio under 1.5～3.0MPa be 30～40%; It is 5.5～10.0 outward transport soil utilizations that mud after press filtration regulates pH value with unslaked lime, or interpolation unslaked lime adjusting Ca/S mol ratio is 1.0～1.2 rear incineration disposals.

2. the method for claim 1, is characterized in that hydrothermal reaction kettle used is the hydrothermal reaction kettle of tool agitating function, and reaction is carried out under 150 ℃～160 ℃ of temperature, pressure 400kPa～600kPa, stir speed (S.S.) 100～200r/min condition.

3. the method for claim 1, is characterized in that described former raw sludge is from municipal sewage plant.