The content of the invention
For the drawbacks described above of prior art, it is an object of the invention to provide a kind of waste gas, sewage coprocessing system and
Method.
Above-mentioned purpose of the invention is achieved through the following technical solutions:
In a first aspect, the present invention provides a kind of waste gas sewage cooperative processing method, comprise the following steps:
Cause that the mixture of sewage and activated sludge, the first waste gas are fully contacted by the way of bubble aeration, obtain first
Mixture, first purification gas of purified water and activated sludge, first purification gas are expelled directly out;
As spray liquid, the second waste gas with reverse input fully connects mixture with first purified water and activated sludge
Touch, obtain the mixture of the second purification gas, the second purified water and activated sludge, second purification gas are directly excluded, described
A part in the mixture of the second purified water and activated sludge continues the mixing as the sewage and activated sludge after reclaiming
Component in thing;
Make the mixture and the three wastes of the second purified water described in another part and activated sludge by the way of bubble aeration
Gas is fully contacted, and obtains the mixture of the 3rd purification gas, the 3rd purified water and activated sludge, and the 3rd purification gas are directly arranged
Remove, continue after the Water Sproading in the mixture of the 3rd purified water and activated sludge as the second purified water and activated sludge
Component in mixture.
As a kind of way of realization of the embodiment of the present invention, first waste gas, the second waste gas, the 3rd waste gas be including
Foul smell, particulate pollutant, oxygen, the waste gas of carbon dioxide;Wherein described foul smell includes that mercaptan, ammonia, hydrogen sulfide, volatility are organic
Acid, benzene class.
Used as a kind of way of realization of the embodiment of the present invention, the superior microorganism strain in the activated sludge includes nitrous
Sour bacterium, Nitromonas, denitrifying bacterium.
Used as a kind of way of realization of the embodiment of the present invention, the mixture with the first purified water and activated sludge is spray
Pouring liquid is fully contacted what is specifically carried out in filler spray scrubber with the second waste gas of reverse input.
Used as a kind of way of realization of the embodiment of the present invention, the recovery is specifically:To the 3rd purified water and activated sludge
Mixture carry out press filtration and obtain water, mud cake, and the turbid solution part in the water is reclaimed.
Second aspect, the present invention provides a kind of waste gas sewage coprocessing system, including the first coprocessing system, second
Coprocessing system, the 3rd coprocessing system;Wherein,
First coprocessing system, for by way of bubble aeration by the mixture of sewage and activated sludge,
First waste gas mixes, and obtains mixture, first purification gas of the first treated purified water of collaboration and activated sludge;
Second coprocessing system, is connected with first coprocessing system, for receiving first purification
The mixture of water and activated sludge and as spray liquid, the second waste gas with reverse input is fully contacted, and obtains collaboration treatment
The second purified water and mixture, second purification gas of activated sludge crossed;The mixing of second purified water and activated sludge
A part in thing is input into first coprocessing system;
3rd coprocessing system, is connected with second coprocessing system, for receiving second purification
With the 3rd waste gas be fully contacted for it by way of bubble aeration simultaneously by another part in water and the mixture of activated sludge, is obtained
Must cooperate with the mixture of treated the 3rd purification gas, the 3rd purified water and activated sludge, and to the 3rd purified water with
Liquid portion in the mixture of activated sludge carries out recovery reprocessing.
As a kind of way of realization of the embodiment of the present invention, first coprocessing system, including for accommodating sewage
With the first aeration tank of the mixture of activated sludge, and to the mixing of the sewage and activated sludge by the way of bubble aeration
Thing is input into the first aerating system of the first waste gas.
As a kind of way of realization of the embodiment of the present invention, second coprocessing system, including assisted with described first
With processing system connection, for the mixture of the first coprocessing system the first purified water of gained and activated sludge to be input into second
First slush pump of coprocessing system, and with the mixture of first purified water and activated sludge be spray liquid to being input into the
The filler spray scrubber that second waste gas of two coprocessing systems is fully contacted;Described filler spray scrubber, its side bottom
Portion is provided with the second exhaust gas entrance, top surface and is provided with the second purified gas outlet, bottom surface and is provided with the mixed of the second purified water and activated sludge
Compound is exported;Mixture outlet of second purified water with activated sludge and first coprocessing system, the described 3rd
Coprocessing system is connected, and is recycled to first for the part in the mixture by the second purified water with activated sludge and is cooperateed with place
Reason system, another part are input into the 3rd coprocessing system.
As a kind of way of realization of the embodiment of the present invention, the 3rd coprocessing system, including for receiving second
The purified water of another part second of coprocessing system output is exposed with the second aeration tank of the mixture of activated sludge, using bubble
The mode of gas is input into the second aerating system of the 3rd waste gas and to the 3rd to the mixture of second purified water and activated sludge
Liquid portion in the mixture of purified water and activated sludge reclaim the recovery and processing system of reprocessing.
Used as a kind of way of realization of the embodiment of the present invention, the recovery and processing system includes:
Be arranged at second aeration tank bottom for by the 3rd purified water in the second aeration tank and activated sludge
Second slush pump of mixture output;
The 3rd purified water and the mixture of activated sludge to the output of the second slush pump carry out press filtration acquisition pressing filtering liquid, mud cake
Filter pressing dehydrator;Wherein, the filter pressing dehydrator is provided with cake outlet for discharging mud cake and for discharging pressing filtering liquid
Pressing filtering liquid export, the pressing filtering liquid outlet branches turn into for by pressing filtering liquid it is muddy partially recycled enter the second aeration tank it is muddy
Turbid liquid pipe road and the clarified solution pipeline by the clarification part discharge system in pressing filtering liquid.
Compared with prior art, there is following beneficial effect in the present invention:
Of the invention waste gas is cooperateed with the purified treatment of sewage is carried out, the technology of the real category treatment of wastes with processes of wastes against one another, is reduced sewage and is given up
The construction investment of the treatment facility of gas and operating cost, are greatly reduced carbon emission.
Specific embodiment
In order to be better understood from the technical scheme of the application, the embodiment of the present application is retouched in detail below in conjunction with the accompanying drawings
State.
It will be appreciated that described embodiment is only some embodiments of the present application, rather than whole embodiments.Base
Embodiment in the application, those of ordinary skill in the art obtained under the premise of creative work is not made it is all its
Its embodiment, belongs to the scope of the application protection.
The term for using in the embodiment of the present application is the purpose only merely for description specific embodiment, and is not intended to be limiting
The application." one kind ", " described " and " being somebody's turn to do " of singulative used in the embodiment of the present application and appended claims
It is also intended to include most forms, unless context clearly shows that other implications.
Depending on linguistic context, word as used in this " if " can be construed to " ... when " or " when ...
When " or " in response to determining " or " in response to detection ".Similarly, depending on linguistic context, phrase " if it is determined that " or " if detection
(condition or event of statement) " can be construed to " when it is determined that when " or " in response to determine " or " when the detection (condition of statement
Or event) when " or " in response to detection (condition or event of statement) ".
The embodiment of the present invention provides a kind of waste gas sewage cooperative processing method, comprises the following steps:
Cause that the mixture of sewage and activated sludge, the first waste gas are fully contacted by the way of bubble aeration, obtain first
Mixture, first purification gas of purified water and activated sludge, first purification gas are expelled directly out;
As spray liquid, the second waste gas with reverse input fully connects mixture with first purified water and activated sludge
Touch, obtain the mixture of the second purification gas, the second purified water and activated sludge, second purification gas are directly excluded, described
A part in the mixture of the second purified water and activated sludge continues the mixing as the sewage and activated sludge after reclaiming
Component in thing;
Make the mixture and the three wastes of the second purified water described in another part and activated sludge by the way of bubble aeration
Gas is fully contacted, and obtains the mixture of the 3rd purification gas, the 3rd purified water and activated sludge, and the 3rd purification gas are directly arranged
Remove, continue after the Water Sproading in the mixture of the 3rd purified water and activated sludge as the second purified water and activated sludge
Component in mixture.
In the above method, cause that the mixture of sewage and activated sludge, the first waste gas are abundant by the way of bubble aeration
Contact, obtains mixture, first purification gas of the first purified water and activated sludge, and first purification gas are expelled directly out;
The step is specially:First waste gas changes into tiny bubble in the presence of aerator, minute bubbles and sewage with
The mixture of activated sludge is fully contacted, and oxygen contained therein, carbon dioxide are absorbed in causing activated sludge by activated sludge
Microorganism bred, acidic components in sewage, the first waste gas, basic component are neutralized, while the micro- life in activated sludge
Thing is adsorbed by organic pollution in waste water, the first waste gas etc., absorbed, converted and removed removal organic polluter.
In the step of some embodiments, the superior microorganism strain in the activated sludge includes Nitrosomas, nitre
Sour bacterium, denitrifying bacterium.Under aerobic conditions, ammonia nitrogen is oxidized into nitrite and nitrate, including two by nitrobacteria
Fundamental reaction step:It is the reaction of nitrite to be participated in mineralized nitrogen by Nitrosomas;Nitromonas participate in by nitrite
It is converted into the reaction of nitrate;Nitrosomas and Nitromonas are all chemoautotrophic bacterias, and they utilize CO2、CO3 2-、HCO3-Deng as
Carbon source, by NH3、NH4+Or NO2-Redox reaction obtain energy.In addition, there is anti-nitration reaction in denitrifying bacterium:Lacking
Under the conditions of oxygen, the nitrite and nitrate reduction that nitration reaction is produced are escaped for nitrogen from sewage, are removed so as to reach
The purpose of nitrogen;In denitrification process, denitrifying bacterium needs organic carbon source (such as carbohydrate, alcohols, organic acid) as electricity
Sub- donor, using NO2-、NO3-In oxygen carry out anaerobic respiration.
In the above method, the mixture with first purified water and activated sludge as spray liquid, with reverse input the
Two waste gas are fully contacted, and obtain the mixture of the second purification gas, the second purified water and activated sludge, and second purification gas are straight
Run in and remove, the part in the mixture of second purified water and activated sludge continues as the sewage and activity after reclaiming
Component in the mixture of sludge;
The step is specially:First purified water is transfused in spray equipment with the mixture of activated sludge, as spray liquid,
Spray from top to down, the second waste gas is input into from bottom to top from spray equipment bottom, the first purified water of reverse input is dirty with activity
The mixture of mud is fully contacted with the second waste gas, and the contaminant component in the two occurs neutralization of acid with base, while the first purification
Water is adsorbed by organic pollution in the second waste gas etc., absorbed, being turned with the microorganism in the mixture of activated sludge
Change and remove removal organic polluter, absorb oxygen, carbon dioxide and bred.
In certain embodiments, the step occurs in filler spray scrubber, and 2-3 is set in described filler spray scrubber
Layer filler, spray nozzle is provided with every layer of filler.
In certain embodiments, the type of filler includes but is not limited to Pall ring in described filler spray scrubber.
In certain embodiments, the material of filler is stainless steel, plastics, ceramics etc. in described filler spray scrubber.
In the above method, the mixing of the second purified water described in another part and activated sludge is made by the way of bubble aeration
Thing is fully contacted with the 3rd waste gas, obtains the mixture of the 3rd purification gas, the 3rd purified water and activated sludge, the 3rd purification
Gas is directly excluded, continue after the Water Sproading in the mixture of the 3rd purified water and activated sludge as the second purified water with
Component in the mixture of activated sludge.
In certain embodiments, described recovery is specifically to carry out press filtration to the mixture of the 3rd purified water and activated sludge,
Obtain water, mud cake.
In certain embodiments, the moisture content of the mud cake is less than 40%.
In certain embodiments, the filter press that the press filtration is used is with filter cloth, intermittent operation filter press;Institute
It is defined with the species to filter press, primarily to ensuring relatively low moisture content of the cake, filter cloth and the mud film that is formed to filter
The good filtration of liquid, pollutant concentration therein being reduced as far as possible, the follow-up cost of sewage disposal of filtrate is reduced, mud cake is relatively low
Power consumption is greatly decreased when moisture content means that its volume significantly reduces, burns.
In certain embodiments, described recovery is specifically to reclaim the turbid solution part during the press filtration obtains water.
In certain embodiments, the judging basis of the turbid solution are:Concentration of suspension in water is more than or equal to 20mg/L.
In the above-mentioned methods, the waste gas includes foul smell, particulate pollutant, oxygen, carbon dioxide;The foul smell such as sulphur
Alcohol, ammonia, hydrogen sulfide, VFA, aromatic compound etc..
For the ease of understanding the above method, inventor is described in further detail as follows:
Step one, one kind contains foul smell (such as mercaptan, ammonia, hydrogen sulfide, VFA, aromatic compound), sulphur
The pollutants such as oxide, nitrogen oxides, hydrophobicity fine particle and oxygen, the waste gas of carbon dioxide are pumped into filler by air-introduced machine
In spray scrubber, its spray liquid is used and contains carbohydrate, ammonia nitrogen, nitrate nitrogen, hydrogen sulfide, phosphorus compound, suspension, work
Property the pollutant such as sludge and in the sewage of strong basicity;In filler spray scrubber, waste gas and sewage are fully contacted, activated sludge
Absorb oxygen, carbon dioxide to adsorb various pollutants, absorb, convert and remove, bred activated sludge, sewage it is strong
Alkalescence is also neutralized by the acidic materials in waste gas;
Step 2, reacted sewage flows out filler spray scrubber, and into aerobic aeration pond, aeration tank bottom is provided with exposure
Device of air, gases used is to contain pollutant and the oxygen such as foul smell (such as mercaptan, ammonia, hydrogen sulfide, VFA, benzene class)
The waste gas of gas, carbon dioxide, aerator is translated into tiny bubble and enters sewage, is fully contacted with sewage, activated sludge
Absorb oxygen, carbon dioxide to adsorb various pollutants, absorb, convert and remove, bred activated sludge, sewage it is strong
Alkalescence is also neutralized by the acidic materials in waste gas;Also added with suspended porous filler in aerobic aeration pond, thereon can adhesion of microorganisms,
Biomembrane is formed, the various pollutants can preferably adsorb, absorb, converting in waste gas, sewage greatly improve treatment effeciency;
Step 3, aerobic aeration bottom of pond portion is provided with sewage (waste water) recirculating pump, enters during sewage in pond is delivered into filler spray scrubber
Row reaction;Aerobic aeration bottom of pond portion is provided with filter press feed pump, and sewage is delivered into plate compression dewaterer (forms mud on its filter cloth
Filter effect increases after film, equivalent to the film of membrane bioreactor (MBR), its advantage be can with the removal of mud cake constantly more
Newly, be not easily blocked, and formed moisture content of the cake it is very low, subsequent treatment expense can be greatly reduced) in carry out filter-press dehydration, will
Residual active sludge and suspension formed mud cake (film of membrane bioreactor can only thickened sludge, and mud cake can not be formed, still need to
Device for dehydrating sladge waste) removal, pressing filtering liquid outward appearance does reflow treatment in before as clear as crystal state, in being cut after as clear as crystal state
Discharge is shifted to, most pollutants therein are thus eliminated, follow-up sewage disposal burden is significantly reduced.
Fig. 1 is referred to, the embodiment of the present invention also provides a kind of waste gas sewage coprocessing system 100, including the first collaboration
Processing system 10, the second coprocessing system 20, the 3rd coprocessing system 30;Wherein,
First coprocessing system 10, for by way of bubble aeration by the mixing of sewage and activated sludge
Thing, the mixing of the first waste gas, obtain mixture, first purification gas of the first treated purified water of collaboration and activated sludge;
Second coprocessing system 20, is connected, with first coprocessing system 10 for receiving described first
The mixture of purified water and activated sludge and as spray liquid, the second waste gas with reverse input is fully contacted, is cooperateed with
The second treated purified water and mixture, second purification gas of activated sludge;Second purified water and activated sludge
A part in mixture is input into first coprocessing system 10;
3rd coprocessing system 30, is connected, with second coprocessing system 20 for receiving described second
Another part in purified water and the mixture of activated sludge is simultaneously fully connect it with the 3rd waste gas by way of bubble aeration
Touch, obtain the mixture of collaboration treated the 3rd purification gas, the 3rd purified water and activated sludge, and purify to the described 3rd
Water carries out recovery reprocessing with the liquid portion in the mixture of activated sludge.
Above-mentioned first coprocessing system 10, including for accommodating the first aeration tank of sewage and the mixture of activated sludge
11, and it is input into the first aerating system of the first waste gas to the mixture of the sewage and activated sludge by the way of bubble aeration
12;
In certain embodiments, first aeration tank 11 is provided with the to its mixture for being input into sewage and activated sludge
One mixture inlet 111;First aerating system 12 includes some first waste gas horizontal pipes 121 and is arranged at described every
Some first aeration tubes 122 on first waste gas horizontal pipe 121.
In certain embodiments, the first waste gas horizontal pipe 121 is vertical with the first aeration tube 122.
In certain embodiments, the side for being aerated direction and first mixture inlet 111 of first aeration tube 122
To opposite.
In certain embodiments, the bottom surface 112 of first aeration tank 11 is oblique, and side is higher than opposite side, relatively low
Side be recessed to form the first kerve 113.
In certain embodiments, the first suspended porous filler 13 is also added with first aeration tank 11, first suspends
Biomembrane can be gradually formed on porous aggregate 13, biochemical reaction efficiency can be improved;Activated sludge concentration higher cannot kept
When, the presence of the biomembrane on the first suspended porous filler 13 can guarantee that biological capacity higher in system.
Above-mentioned second coprocessing system 20, including be connected with first coprocessing system 10, for by first association
The first mud of the second coprocessing system 20 is input into the mixture of activated sludge with the first purified water of gained of processing system 10
Pump 21, and with the mixture of first purified water and activated sludge be spray liquid to being input into the of the second coprocessing system 20
The filler spray scrubber 22 that two waste gas are fully contacted;Described filler spray scrubber 22, its side bottom is provided with the second waste gas
Entrance 221, top surface is provided with the mixture outlet that the second purified gas outlet 222, bottom surface is provided with the second purified water and activated sludge
223;Mixture outlet 223 of second purified water with activated sludge and first coprocessing system 10, the described 3rd
Coprocessing system 30 is connected, and being recycled to first for the part in the mixture by the second purified water with activated sludge cooperates with
Processing system 10, another part is input into the 3rd coprocessing system 30.
In certain embodiments, first slush pump 21 is arranged at the first aeration of first coprocessing system 10
The bottom of pond of pond 11.
In certain embodiments, first slush pump 21 is arranged in first kerve 113.
In certain embodiments, second purified gas outlet 222 is connected to contribute to the second waste gas from the second waste gas
The imported fill spray scrubber 22 of entrance 221, the second purification gas export filler spray washing from the second purified gas outlet 222
The air-introduced machine 23 of tower 22.
In certain embodiments, the type of filler includes but is not limited to Pall ring in described filler spray scrubber 22.
In certain embodiments, the material of filler is stainless steel, plastics, ceramics etc. in described filler spray scrubber 22.
In certain embodiments, second purified water is divided into two points with the end of mixture outlet 223 of activated sludge
Branch pipe(tube), i.e. the first recovery channel 224, the second recovery channel 225, first recovery channel 224 cooperate with processing system with first
System 10 is connected, and second recovery channel 225 is connected with the 3rd coprocessing system 30.
In certain embodiments, first recovery channel 224 is provided with the first valve 226, second recovery channel 225
It is provided with the second valve 227;First valve 226 is used to control the second purified water to cooperate with place with the mixture input first of activated sludge
Reason system 10, the second valve 227 is used to control the second purified water to be input into the 3rd coprocessing system with the mixture of activated sludge
30。
Above-mentioned 3rd coprocessing system 30, including for receiving another part the of the output of the second coprocessing system 20
Second aeration tank 31 of the mixture of two purified waters and activated sludge, by the way of bubble aeration to second purified water with
The mixture of activated sludge is input into the second aerating system 32 of the 3rd waste gas and to the 3rd purified water and the mixture of activated sludge
In the recovery and processing system 33 that is recycled of liquid portion.
In certain embodiments, second aeration tank 31 is connected with second recovery channel 225.
In certain embodiments, the bottom surface 311 of second aeration tank 31 is oblique, and side is higher than opposite side, relatively low
Side be recessed to form the second kerve 312.
In certain embodiments, second aerating system 32 includes some second waste gas horizontal pipes 321 and is arranged at
Some second aeration tubes 322 on the second waste gas horizontal pipe 321.
In certain embodiments, the second waste gas horizontal pipe 321 is vertical with the second aeration tube 322.
In certain embodiments, the aeration direction of second aeration tube 322 and second recovery channel 225 input the
Two purified waters are in opposite direction with the mixture of activated sludge.
In certain embodiments, second aerating system 32 is connected with first aerating system 12, specifically refers to
Fig. 1.
In certain embodiments, the recovery and processing system 33 includes:
Be arranged at the bottom of the second aeration tank 31 for the 3rd purified water in the second aeration tank 31 and activity is dirty
Second slush pump 331 of the mixture output of mud;
The mixture of the 3rd purified water and the activated sludge of the output of the second slush pump 331 is carried out press filtration obtain pressing filtering liquid,
The filter pressing dehydrator 332 of mud cake;Wherein, the filter pressing dehydrator 332 is provided with the cake outlet 3321 for discharging mud cake and uses
In the pressing filtering liquid outlet 3322 of discharge pressing filtering liquid, 3322 branches of pressing filtering liquid outlet turn into and are used for the muddy portion in pressing filtering liquid
Divide the turbid solution pipeline 3323 and the clarification liquid pipe by the clarification part discharge system in pressing filtering liquid for being recovered into the second aeration tank 31
Road 3324.
In certain embodiments, the turbid solution pipeline 3323, clarified solution pipeline 3324 pass through switching valve 3325 and press filtration
Liquid outlet 3322 is connected.
In certain embodiments, second slush pump 331 is arranged at the second kerve 312 of second aeration tank 31
In.
In certain embodiments, the filter pressing dehydrator 332 is that (filter cloth uses sewage disposal activated sludge pressure with filter cloth
Conventional use of specification is filtered, main or by being formed mud film is filtered, the as clear as crystal just thickness of explanation mud film of water outlet
Met requirement), Batch Pressure Filtrating Equipment;Why the species of filter press is defined, primarily to ensuring produced mud
Cake moisture content is relatively low, and power consumption is greatly decreased when the relatively low moisture content of mud cake means that its volume significantly reduces, burns.
In certain embodiments, the second suspended porous filler 34 is also added with second aeration tank 31, second suspends
Biomembrane can be gradually formed on porous aggregate 34, biochemical reaction efficiency can be improved;Activated sludge concentration higher cannot kept
When, the presence of the biomembrane on the second suspended porous filler 34 can guarantee that biological capacity higher in system.
In the above-described embodiments, the first described waste gas, the second waste gas, the 3rd waste gas are specifically referred to by different entrances
Enter containing the pollutant such as including foul smell, oxygen, carbon dioxide waste gas;The foul smell such as mercaptan, ammonia, hydrogen sulfide, volatilization
Property organic acid, benzene class etc..
In the above-described embodiments, the first suspended porous filler 13 and the second suspended porous filler 34 are waste water common at present
The filler applied in treatment.
The invention belongs to treatment of wastes with processes of wastes against one another technology, the construction investment of the treatment facility of sewage and waste gas can be greatly reduced and runs into
This, is greatly reduced carbon emission.
The principle of present invention collaboration treatment:The growth needs of Microbial Communities in Activated Sludge it is various containing carbohydrate, nitrogen,
The nutriment of phosphorus, sulphur, and these materials are exactly often the pollutant in waste gas and sewage;Some growth of microorganism need to absorb
Oxygen and release carbon dioxide, some growth of microorganism do not need oxygen and need absorbing carbon dioxide (such as nitrifier), waste gas
In carbon dioxide belong to sour gas, can neutralize the alkalescence of sewage, save the addition for neutralizing medicament, thus can be fully sharp
With the oxygen in waste gas, carbon dioxide, energy resource consumption and carbon emission are reduced.Can gradually shape on the filler of filler spray scrubber
Into biomembrane, biochemical reaction efficiency can be improved.Contain zoogloea in activated sludge and biomembrane, mucus can be secreted (for microorganism
Extracellular polymeric, its composition is mainly polysaccharide), the adsorbable hydrophobicity fine grained for being difficult to wash gone in removing exhaust gas
Thing.
Above example is only used to illustrate the technical scheme of the application, rather than its limitations;Under thinking of the invention, with
Can also be combined between technical characteristic in upper embodiment or different embodiments, step can be realized with random order,
And in the presence of many other changes of different aspect of the invention as described above, for simplicity, they are provided not in details;
Although being described in detail to the present invention with reference to the foregoing embodiments, it will be understood by those within the art that:Its according to
The technical scheme described in foregoing embodiments can so be modified, or which part technical characteristic is equally replaced
Change;And these modifications or replacement, do not make the model of the essence disengaging various embodiments of the present invention technical scheme of appropriate technical solution
Enclose.