CA1051566A - Raw liquid waste treatment system and process - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A raw sewage treatment process is disclosed in which substantially all the non-dissolved matter, which is suspended in the sewage water is first separated from the water, in which at least organic matter is dissolved. The non-dissolved material is pyrolyzed to form` an activated carbon and ash material without the addition of any conditioning agents. The activated carbon and ash material is added to the water from which the non-dissolved matter was removed. The activated carbon and ash material adsorbs the organic matter which is dissolved in the water and is thereafter supplied in a counter current flow direc-tion and combined with the incoming raw sewage to at least facilitate the separation of the non-dissolved settleable materials from the sewage water. The used carbon and ash material together with the non-dissolved matter which was separated from the sewage water are pyrolyzed to form the activated carbon and ash material.

Description

o l~I C ~ r~o~

The invention described herein was made in the performance of work under a N~SA contract and is subjcct to tlle provisions of Section 305 of the National ~eronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 USC 2~57).
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~CKGROUN~ OF Tll~ INVENTION

1. Field of the Invention~
The present invention generally relates to a waste water treatment process and, more particularly, to a process and system for treating raw liquid waste which contains organic matter which is dissolved and/
or suspended in the liquid.

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2. Description of the Prior ~rt:

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The ~robl~ms facing municipalities in treating raw sewage, which is one ~orm of waste water, are well : ~ , ~;nown. The sewage consists of water contaminated by ; : ..
organic and inorganic matter which is dissolved in the water as well as organic and inorgallic matter wilich is not dissolved, namely suspended in t}~e water~ ~TIle .
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S~ i6 latter-type contaminant m~y be divided into two graups of materials, those which are settleable in the water and those which are not settleable and tend to float on top of the water. The function of any sewage treat-ment system is to separate substantially all thesuspended matter from the water as well as to greatly reduce the organic matter dissolved therein, and there-after dispose of the separated matter.

The separated contaminants which are mixed 0 with some water and therefore are in slurry form, ` often referred to as sludges, are biologically active until stabilized by subsequent treatment~ The stabilization is genexally achieved by bioLogical digestion. Such digestion is sometimes used to produce combustible gases such as methane, useful as a source of enerqy. Howeverr the remaining solid material presents diEficult and costly disposal problems.
Digested ~humic) solids have been processed to fertili~ers and soil conditioners. lhis practice is generally not economical and the quantity available greatly exceeds the market demands. Municipalities are findinc3 it increasinqly difficult to dispose o~ the remaining sludge solids in waterways, oceans or land-fills, due to their ecological impact. Legislation ~.
is being considered to reduce and eventually ~orbid such `~ solid d~lmpinq. Thus , disposal of solids, produced by prior art treatment systems, present a very severe pro-` ~lem, in addition to the high disposal cost. Other .:`' .~

3~152 ., ~Sl56f~
disadvantages of prior art systems in which biological digestion is employed include the large land area of aeration basins required for their operation, ~nd the releasillg of o~fensive odors. ~lso, prior art systems are relatively inc~ficient and must be carefully monitored and controlled to prevent any unbalancing in the biological digestion. That is, the types and/or amounts of contaminants per liter of water must be controlled to be within specified limits in order not to upset the biological digestion process.
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~n attempt to reduce the amount of solids ~; re~uiring disposal is described in U.S. Yatent No.
3,640,820. Therein, a sewage treatment process is described in which the sewage sludges are converted into an active material which is used in the process. ~-Several disadvantages of the system described in said ; patent are apparent. The proposed process is on~
employing biological digestion and therefore suffers from all of the shortcomings, hereinbefore discussed. In addition, it reguixes the use of a conditioning agent in the active material production.

In the February 22, 1972 issue of Chemical ~ngineerin~, a process developed by DuPont and known as P~CT for Powdered Activated Carbon Treatment is ;~ 25 disclosed. Therein, activated carbon, which is not ~ produced fro~ contaminants in liquid waste is required, :` ~

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ther~by increasing process costs. ~lso, t~le amount of material, requiring final disposal, is not reduced and therefoxe the disposal cost is high and the disposal problems are not solved~

S O~J~C~l~S ~ND SUM~Y OF '~'~IE INV~NrrION
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It is a primary object of the present invention to provide a new sewage treatment s~stem and process.

Anothex object of the invention is to provide a sewage treatment process in which the contaminants are used to form a material without the addition of a conditioning agent, with the material being used in ~ the treatment process.
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Yet another object of the invention is to provide a highly efficient sewa~e treatment process in which biological processing is no~ required and in which substantially all the objected-to contaminants are removed in the process by means of a material which is formed from the contaminants, with the amount of material requiring final disposal being inert and . . ~ . .
~ only a fraction of the total amount of contaminant . I;

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~hese and other objects of the invention are achieved by a treatment process in which at least the non-dissolved matter, hereinafter also referred to as solids of screened raw sewage are separated in a primary settler from the water which contains the dissolved organic and inorganic matter. As will be pointed out hereinafter, the separation of the non-dissolved settleable solids from the water is facilitated by the addition of a slurry o~ an activated carbon and ash material which has been used down-stream in the process.
The non-dissolved settleable soIids together with the slurry of the activated carbon and ash material which settle on the bottom o the primary settler are removed as a wet slurry-and-primary-sludge mixture from the primary settler and supplied to a filter. Therein, the mixture is supplied to a pyrolysis reactor. The latter is also supplied with the non-dissolved non-; settleable contaminants (solids) from the top of the primary settler.

In the reactor, the material supplied thereto is converted into a material W}liC}I consists of activated carbon and ash. The activated carbon and ash material is iormed into a primary slurry by the addition of water and is added to the water rom which the non-dissolved matter has been separated in the primary settler.
The water and the activated carbon and a~h n~e -6- :

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- llD51S~i6 introduced illtO a secondary settler, wherein a very high percenta~e of the organic matter, which is dissolved in the water, is adsorbed onto ~he carbon and ash~ The latter, after adsorbing the dissolved organic matter is removed rom the secondary settler, as a secondary slurry, and is directed to the primary I settler into which the screened raw sewage is initially introduced. The addition of the secondary slurrv, i.e., tlle partially used carbon and ash material to the screened ra~ sewage greatly reduces the separation time of the non-dissolved settleable matter from the sewage water. In addition, the pxesence of the carbon j~
in the slurry-and-primary-sludge mlxture which is .; ~ !
supplie~ to the filter acts as a filtering aid. It promotes faster dewatering of the mixture and therefore drier material for the pyrolysis step. ,, The novel features of the invention are set ;', :
~ forth with particularity in ~e appended claims. The : -invention will best be understood from the following description when read in conjunction witll the : , ;l accompanying drawings.

BRIEF DESCRIPTION OF TflE D~A~IINGS

. :' r ~` Figuxe 1 is a general block diayram of the l novel system and process of the present invention; and :~
Figure 2 is a simplified cross sectional view l of one possible embodiment of a pyrolysis reactor, shown r~
'.'' , in Figura 1.

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L)L::SCI~IPTIO~l OF THE PREFER~ED L.t~UODI~ NTS

~ttention is now directed to the dra~ing wherein numeral 10 designates a primary settler of a sewage treatment system in accordance with the present invention. As is known, raw sewage or wastewater con-sists of water contaminated by various organic and inorganic m~terials, some of which are dissolved in the water while others are non-dissolved and are suspended ~lerein. The non-dissolved suspended materials are either of the settleable or the non-settleable types. The latter tends to float on top of the ,F
water. The ~unction of any raw sewage treatment process is to remove the non-dissolved suspended materials, and as much as possible of the dissolved organic ` 15 matter ~rom the water. r :
~`~ In accordance with the present invention, ~j raw s~wage is first screened by appropriate means ., .
`~ (not shown) in a manner well known in the art to remove ~`~ all relatively large objects as well as most of the sand in the raw sewage. The screened raw sewage, hereinafter simply referred to as screened sewage, which is fed to the system on line 11 is introduced into a ':: 1 contactor or 10cculator 12 wherein it is mixed with an incoming secondary slurry. ~s will be described hereinafter, the incoming secondary slurry is ~ ', , . '-:` `

~ )S156~
a slurry of activated carbon and ash material which wa~ partially used down stream. ~fter appropriate mixillg, the screened sewage Wit}l the secondary slurry are fed to tlle prima~y settler 10.

In the present invention, substantially all of the non-dissolved suspended solid material is removed from the sewage water in settler 10. The non-settleable material which is generally skimmed of~ the top of the water is supplie~ to a pyrolysis j 10 reactor 15 directly via line 16. The settleable I material, ~enerally referred to as primary sludge, ` whicl~ is quite ~et, i.e., has a hiqh water content,.
is supplied to a dewatering stage 17, such as a ~ilter. I
The function of the filter 17 is to dewater the ~
primary sludge. The dewatered solids, generally in !':
the form of relatively dry cakes of solids, are 1, , ~
, supplied to the reactor v:ia line 18. Thus, the reactor 15 ls supplied with all the non-dissolved ~ ;
suspended matter, both organic and inorganic, pxesent in the incoming screened sewage. The sewage ~Jater from which all the suspended matter was removed in ; settler 10, is supplied via line 21 to a contactor .: :
22 and therefrom to a secondary settler 20. The water from filter 17, which is relatively free of any suspended matter is preferably combined with the effluent of settler 10 in line 21 or in contactor 22, as represented by daslled line 23.

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~~~ 73/152 ~OS~S66 ~s is appreciated, the settling time of settleable contaminants in screened sewage is quite lon~. It has been discovered that the settling time ; for all non-dissolved settleable matter can be reduced to less -than an hour by mixiny the screened sewage in the contactor 12 with a material consisting of activated carbon and ash and thereafter introducing - the mixture into settler 10 wherein settlin~ ta};es place. The settling rate of the non-dissolved settleable matter seems to depend on the ash content as well as the carbon particle size o the activated ' carbon and ash material. Tests with an activated carbon and ash material with 50~ ash and particle size in the range of 200 mesh, produced total settling (in settler 10) of all settleable matter in 35 -` minutes, as compared with com~ercial carbon containing little or no ash which showed very poor settling characteristics. ~ith such material, fine matter xemained in suspension for as long as 24 hours.
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The activat~d carbon tends to adsorb to some extent, various substances, such as DDT, phosphates, nitro~enous substance, some metal salts, and organic !
complexes of mercury which are not easily separable from water by other means. It has been discovered that thc additioll of the carbon and ash material reduces turbidity, removes odors and reduces foaming.

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``` ~05~66 ~ s will be pointed out h~reinafter, in the novel process of the pres~nt invention, an activated carbon and ash material is produced in reactor 15 from all t~le contamillants extracted from the sewaye water.
This material after being partially used to extract - most of the organic matter which is dissolved in the water is mixed with screened sewage in contactor 12 and thereafter, the mixture is supplied to the primary settler 10 to facilitate the separation of the non-dissolved settleable matter from the water. In accordance with the present invention, the material which is supplied to the filter 17 is not only primary sludcJe (non-dissolved settleable matter) but rather a mixture of a carbon and ash slurry and primary sludge.
Alternately stated, it is a slurry of a mixture of carbon and ash particles and primary sludge. ~he '~
presence of the carbon in this mixture is very helpful in the filtering operation~ The carbon acts as a iltering aid. It tends to promote faster filtering and higher dewatering of the mixture. Thus, drier material is supplied from the filter 17 to the reactor 15.
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From the foregoing, it is thus seen that the reac~or 15 is supplied with the relatively dry solids from tlle filter 17 and ~ith the non~settleable sewage con taminants from the primary settler 10. In the reactor, all the supplied material is pyrolyze~ under ~, r ,~

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1[1~1566 controlled temperature and pressure conditions and is converted into an activated material which consists of activated carbon and ash. This is achieved without the addition of any conditionin~ agents. ~s part of the pyrolysis operation, various ~ases, including combustible gases, such as methane and carbon monoxide, are released. Such gases are used to provide at least par. of the energy needed for the system's operation.

Tne ash component represents the pyrolyzed inorganic matter, the major components of which are believed to be calcium, magnesium, iron, phosphates, ; sulphates and oxides. The carbon component represents the pyrolyzed organic matter. ~ careful inspection of the material reveals that it does not consist of a mixture of separate carbon particles and ash particles but rather of particles which are a combination i of carbon and ash. It has been noted that`the activated carbon and ash material pxoduced from typical domestic screened raw sewage has about a 50% ash content which is very useful in the separation of the settleable solids from the water in the primary settler lO.
' ; It should be stressed that the material produced in the rcactor 15 is activated rather than r inactivated carbon and ash. Activated carbon and various 25 tec`~niques of producin~ it are described in a book ; entitled "~ctivated Carbon" by John ~. }~ssler, ; publishecl in 1963 by Ch~mical Publishin~ Companyj Inc., of Ne~r York.
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3L~S~i66 Tll~ fresh activated carbon and ash from the reactor 15 is combined with clean water to form a primary carbon-ash slurry which is supplied to the con-tactor 22 via line 2~. The latter may incorporate a pum~ 25 to pump the primary slurry to the contactor 22. The pump which may be a centrifugal pump may also be used to control the average size of the particles of the carbon and ash material. The fresh activated carbon and ash is mixed in contactor 22 with the water, from which all non-dissolved matter was removed and which now contains only the dissolved matter, both organic and inorganic. This mixture is then supplied to the secondary settler 20. Therein the activated ; carbon and ash adsorbs a very hign percentage of the dissolved organic matter and settles on the bottom of settler 20. F
' ' ' The adsorption eficiency was found to be quite high due to the fact that the adsorbing carbon ; is the fresh carbon from the reactor 15. ~lso, since ;~
the water in settler 20 is free from any non-dissolved contaminants such as greases, which were removed in the primary settler 10, none of the carbon-ash particles becomes coated with any matter which may inhibit the adsorbability of organic matter thereon. The activated carbon and ash material is capable of aclsorbing the organic matter dissolved in the water even at relatively low organic matter concentration.
It has been discovered that very good results are achieved . ' ' ~

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lOS~SG6 when tl~e primary slurry contains an amount (by weight) of carbon about equal to the amount of total organic matter in the original screened s~ewage which enters the prim~ry settler 10. After an appropriate contact S time, e.g., 20 minutes, ~he activated carbon and ash, which adsorbed the organic matter is removed as a secondary carbon-asll slurry from settler 20 and i5 supplied via line 26 to the contactor 12, to which the screened sewage is supplied.

The reasons or adding the secondary carbon-ash slurry to the raw sewage have bèen previously discussed. Even though the carbon and ash material in the secondary slurry was already partially used in the secondary settler 20, its usefulness is not at an end. -`
It facilitates the separation of the non-dissolved suspended matter of the sewage in addition to adsorbing or otherwise removiny some materials which are difficult to othe~rise separate from the water. The partially used activated carbon and ash in the primary settler 10 is also believed to adsorb some of the inorganic : . .
and organic matter dissolved in the water. ~lowever, its primary function is to ~acilitate the separation of non-dissolved matter from the sewage water.

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;~ From the foregoing, it is thus seen that in ~ 25 accorc~ance with the present invention, an activated : ,~
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carbon and ash material is formed from the contaminants ,`

of the screened sewage without the addition of any ., ,~ .

` -14-:. , ,, , . .. .. _ ~051'~6 conditioning agents. This activated carbon and ash matcrial is first used to adsorb most of the organic matter dissolved in the sewaye water from which non-dissolved matter was previously removed. Then, 5 the p~rtially used carhon and ash material is mixed with the incoming raw sewage. The presence of the material facilitates the separation of non-dissolved settleable matter from the sewage water by greatly reducing the settling time. The mixture of the wet non-dissolved settleable matter, representing primary sludge, together with the used carbon and ash material are then supplied as a slurry-and-sludge mixture to the filter, whose function is to reduce the mixtur2 water content. The carbon present in the mixture acts :
as a filtering aid which increases filtering rates and reduces the water content of the solid materials which ~ are supplied to the reactor 15 for pyrolysis.
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From the foregoing, several significant . . .
; advantages of the present invention should become ap~arent. First, the present invention eliminates the biological digestion stage which is typical of most prior art systems. Its elimination reduces system size, c~mplexity and cost. Secondly, all the material which is needed for the treatment process, i.e., thc activated carbon and ash material is produced .
fxom the scwage contaminants Wi~O~It tlle nced for any additional conditioning agents. Tests of the present invention with typical screened sewage indicate ~, .
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tllat in the pyrolysis step, suficient combustible matter and gases are formed which can provide nearly all the power necessary to sustain the system's opera-tion. Thus, energy from external sources may not be required. ~lso, these tests indicate that the amount of material which has to be disposed of is only about 1/10 the total contaminant materials in the sewage, thereby gr~atly reducing ~le material disposal problem. !

The basic system in accordance with the present invention is effectively a 2-stage system since it includes only the primary and secondary settlers in the water flow ~ath. Laboratory tests indicate that with the present system and process between 87 and 93% of all organic matter can be removed ~rom the .Y
water after passing through the secondary settler. In the prior art, 2-stage systems, with one of the stages being a biological digestio~ stage, only about 80-85% of the organic matter is removed. Thus, the present system is clearly more efficient.

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It is believed that the organic matter xemaining in the water, in settler 20 a~ter it was treated by the fresh activated carbon and ash material r consists o~ matter of high molecular weight which i5 .
generally not adsorbable by carbon. By hydrolyzing the raw sewage in the primary settler or ahead of it, r ,~ .
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~l~ molecul~r weiyht of such m~tter may be lowered so that even a higher percentage of the organic matter will become adsorbed by the carbon. Thus~ hydrolysis may increase the system's efficiency.

S In practice, most of the activated carbon and ash material which is introduced into the ~-secondary settler 20 settles therein and is removed tllerefrom as the secondary carbon-ash slurrv.
~owever, the carbon and ash material includes some very small particles which tend to remain suspended in the water in the secondary settler. They can be removed by passing the water effluent from the secondary settler 20 through an appropriate filter, designated ~ -by numeral 30. The carbon parti~les t~apped by filter 30 may then be removed from the filter in the form o r~.
a fine carbon slurry and thereafter be combined with - the secondary carbon-ash slurry for subsequent use in the primary settler 10. ~lternately, the fine carbon . ~
slurry from filter 30 may ~e supplied directly to the filter 17 as indicated by dashed line 32, for use therein together with the other matter which is supplied thereto from the primary settler 10 It should be appreciated that for the system to be self-sustaining, at least as far as the E~roduction of the activated carbon and ash material, the treated Se~Jage should contain a sufficient amount . .~ r ' ~ _ ............................................... . ..

of organlc contaminants. Processed typical domestic raw sewage contains a sufficient amount of contaminants.
~'he average composition of domestic raw sewage has been described in the literaturc and is well known by those familiar with the art. The present invention is capable of processing sewage with higher than conven-tional contaminant content. The hi~her contaminant ~!
content merely results in tlle production of more activated carbon and ash material which is no way detrimental to the system's operation. The additionalcarbon and ash material may be used as a source of energy. This is not the case in prior art systems in which biological digestion is employed. Therein, the types of contaminants, such as toxic chemicals and/or tlleir amounts cannot exceed certain limits. Otherwise, - the biological digestion process is greatly upset , - ~hich often causes the entire treatment process to be shut down. It is this high sensitivity of prior art .i, .~ ~ .
systems, which employ biological digestion to over-contaminated sewage, ox to liquid wastes which contain - certain contaminants, e.g., chromium, acids, and alkalies, whicn often forces municipalities to iI~ibit various industries from injecting their wastewater into the wast~water networks of the municipalities.
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~lthough ~le invention has been described in connectioll with treatillg screene~ raw sewage, it should be apparent that it is applicable to trea~ any type of waste water, which is contaminated by organic and inorganic ., ~

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materials. Screene~ raw sewage is only one type of waste ~ater. Furthermore, the invention can be used to treat any liquid contaminated by oryanic and inor-ganic materials in any industrial or agricultural - S process. As used herein, the term raw liquid waste -inten~s to refer to any contaminated liquid, including water but not limited thereto. For example, the present invention may be used to treat raw liquid waste produced in an industrial or agricultural process in order to enable the liquid to be reused.
~lso, it may be used to reduce the contaminant content of the liquid waste to permit the liquid to be j injected in the general wastewater network of a neighboring municipality or into the natural surroundings.
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In one embodiment, which was actually reduced ~ to practice, very satisfactory activated carbon and ash `l material was produced in reactor 15 which operated at ~; a temperature between 1200 and 1800 degrees Fahrenheit t660 to 98Z degrees Centigrade) under an atmosphere composed of a mixture of gases. l'he mixture of ~ases, at a pressure slighly higher than atmospheric press~re, was composed of the gases derived from the pyrolysis operation consisting mainly of carbon dioxide, carbon ; 25 monoxide, hydrogen and water vapor in the form of ;~i s~lperheated steam. The pyrolysis reactor 15 consisted ~-` of three principal reaction zones comprised of: Zone 1, watcr cvaporation or drying, Zone 2, carbonization or :`! r : , :

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decomposition, Zone 3, activation or selective oxida-tion, as shown in simplified form in Fiyure 2. The pattern supplied to the reactor unit lines 16 and 18 was introduced into Zone 1 thrcuyh a valve 40. The matter was advanced from zone to zone ~y ral~es supported on a rotatable shaft (not shown). ~leat was provided by a combustion chamber 42. The mixture of gases which was formed served to dry the matter in Zone 1 as well as activate the carbon in Zone 3. As is appreciated, some of the gases, such as methane and carbon monoxide which are combustible, can be used as a source of ener~y. Although, the superheated steam was used to j~;
produce a satisfactory activated carbon and ash, if ~-desired, steam produced from clean water may be used -~

for the carbon activation.
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- Retention time in Zone 3, activation, deter- j mined the degree of activation and varied from 15 minutes to one hour. ~etentlon time is a function oi the r~actor furnace design and can vary from as little as five seconds to as much as five ~lours.
Lon~er times ~or activation tend to produce ~reater activation of the carbon but reduce tlle proportion of carbon and increase the proportion of ash. Lower retention times for activation tend to decrease the !
de~ree of activation and increase the proportion of carbon and decrease the proportion of ash. The activation retention times of lS minutes to one hour .; ~ .
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~05~LS66 ~as founcl to pro~uc~ ~he proper dec3ree of activation o~ tl)c product and t~le proper combination oE carhon and ash for satisfactory operation of the process.
''' It should be appreciated that modifications S may be made in the system and process`hereinbefore ; described without departiny from the spirit of the invention. For example, if the raw liquid waste is o a type in which the non-dissolved settleable matter ~, settles speedily without the addition of any carbon and ash material, the secondary carbon-ash slurry from settler 20 may be supplied directly to the ~ilter as represented by dashed line 44 rather than to contactor 12 and therefrom to the primary settler lO. Also, if the raw liquid waste is highly contaminated so that a larye amount of activated carbon and ash material is produced, some of the material may be supplied directly - to contactor lO rather than through secondary settler 20, while the rest of the material may be used for -adsorbing the dissolved organic matter in the liquid in settler 20. ~lso, although various parts of the system were described as contactors, settlers, ekc., any devices performing e~uivalent functions may be l`
substituted therefor. ~ll such modifications and equivalents are deemed to fall within the scope of the invention as claimed in the appended claims.
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Claims (23)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for treating screened raw liquid waste, characterized by the absence of a biological digestion stage, and including the steps of: receiving screened raw liquid waste which comprises a liquid in which matter is dissolved and non-dissolved matter; mixing the received screened raw liquid waste with a used activated carbon and ash material to form a first mixture; permitting said first mixture to stand for a predeter-mined period for enabling the settling of nondissolved matter in said liquid, together with the used activated carbon and ash material to form a primary sludge; separating the liquid in which matter remains dissolved, representing a first effluent, from said primary sludge; converting said primary sludge to form fresh activated carbon and ash material; mixing at least some of the fresh activated carbon and ash material with said first effluent to form a second mixture; permitting said second mixture to stand for a predetermined interval to enable the fresh activated carbon and ash material therein to absorb matter in said first effluent, and to thereafter settle as a used carbon and ash material;
separating said settled used carbon and ash material from the rest of said second mixture; and transferring the separated used carbon and ash material for direct mixing with said received screened raw liquid waste.

2. A process as described in Claim 1 wherein the step of converting said primary sludge into fresh activated carbon and ash material includes: filtering said primary sludge to reduce the liquid content thereof; pyrolyzing the filtered primary sludge to form a carbon and ash mixture; and activating said carbon in said carbon and ash mixture to form said fresh activated carbon and ash material.

3. A process as described in Claim 1 wherein said non-dissolved matter is said liquid includes floatable matter which floats on top of said liquid when said first mixture is permitted to stand for said predetermined period, and wherein the liquid in said first mixture which represents said first effluent is se-parated from said primary sludge and said floatable matter, before it is mixed with the fresh activated carbon and ash material.

4. A process as described in Claim 3 including the step of mixing the fresh activated carbon and ash material with a clean liquid to form a primary slurry for mixing with said first effluent to form said second mixture.

5. A process as described in Claim 3 wherein after said used activated carbon and ash material is separated from said second mixture there are included the further steps of:
filtering the remainder of said second mixture, representing a second effluent to remove carbon particles therefrom; and adding said removed carbon particles to said used activated carbon and ash for mixing with said removed screened raw waste.

6. A process as described in Claim 3 wherein the float-able matter from which said first effluent was separated is acti-vated together with said primary sludge to form said fresh acti-vated carbon and ash material.

7. A process as described in Claim 3 wherein the amount of used carbon and ash material which is added to the screened raw liquid waste is sufficient to provide an amount of carbon by weight on the order of the weight of organic matter in the screened raw liquid waste.

8. A process as described in Claim 3 wherein said raw liquid waste is raw sewage.

9. A process as described in Claim 3 wherein said raw liquid waste is an industrial liquid waste.

10. A non-biologically-digestive system -for treating screened raw liquid waste comprising: mixing means for mixing screened raw liquid waste which comprises a liquid wherein there is suspended matter and dissolved matter together with a used ac-tivated carbon and ash material to form a first mixture; first set-tlement container means to which said first mixture is transfer-red for a predetermined interval for enabling the settling of at least said suspended matter together with the used activated car-bon and ash material from said liquid to form a first sludge, the remainder of said first mixture representing a first effluent;
converting means for converting said first sludge into a fresh activated carbon and ash material; means for transferring said first sludge to said converting means; means for mixing said fresh activated carbon and ash material with said first effluent to form a second mixture; second settlement container means to which said second mixture is transferred for a predetermined interval to enable the fresh activated carbon and ash material to adsorb matter in the first effluent in said second mixture and to settle in said tank as used activated carbon and ash material, represent-ing a second sludge, with the remainder of said second mixture re-presenting a second effluent, and means for transferring said used carbon and ash material, which represents said second sludge, to said means for mixing to be mixed with the screened raw liquid waste.

11. A system as described in Claim 10 wherein the amount of used carbon and ash material which is transferred to said means for mixing by said means for transferring is sufficient to provide an amount of carbon by weight at least equal to the weight of organic matter in the screened raw liquid waste.

12. A system as is described in Claim 10 wherein there is included filter means, means for applying to said filter means the remainder of said second mixture in said second container after said used carbon and ash has settled in said tank to sepa-rate therefrom any unsettled carbon particles, and means for adding said unsettled carbon particles to said used activated carbon and ash material.

13. In a method for treating liquid waste which in-cludes liquid in which organic and inorganic matter is dissolved, further including nondissolved settleable matter and floatable matter wherein the liquid waste is first introduced into a pri-mary settling tank for settling the nondissolved settleable mat-ter, which is then separated as a primary sludge and supplied to a pyrolyzer to form fresh activated carbon and ash material, at least some of the fresh activated carbon and ash material being thereafter mixed with the liquid derived from the primary settling tank and fed to a secondary settling tank, where the fresh acti-vated carbon and ash material adsorbs matter in the liquid with which it was mixed and settles to the bottom of the secondary set-tling tank as a slurry, the method being characterized by the ab-sence of a biologically-digestive step, an improvement for shor-tening settling time in said primary settling tank, and for in-creasing the adsorption of matter by said fresh activated carbon and ash material, the steps comprising: removing said slurry from said secondary settling tank; mixing said slurry with in-coming liquid waste, prior to its introduction into said primary settling tank to form a mixture; transferring said mixture to said primary settling tank; permitting said mixture to stand in said primary settling tank for a predetermined interval whereby the nondissolved settleable matter and the slurry settle out of said mixture as said primary sludge within a shorter interval than has been previously achieved and said floatable matter floats on said liquid in said primary settling tank; and removing said floatable matter from said primary settling tank to thereby sepa-rate it from the liquid which is subsequently mixed with the fresh activated carbon and ash material for subsequent feeding to said secondary settling tank.

14. In a method as recited in Claim 13 wherein in the improvement the amount of the slurry mixed with incoming liquid waste is sufficient to provide an amount of carbon by weight at least equal to the weight of the organic matter in the liquid waste.

15. In a method as recited in Claim 13, wherein said liquid waste is screened raw sewage.

16. In a method as recited in Claim 13 wherein said liquid waste is industrial waste.

17. In a method as recited in Claim 13 the improvement further including the steps of: filtering the liquid left in said secondary settling tank after removal of said slurry to re-move carbon particles suspended therein; and adding the carbon particles, so removed, to said slurry.

18. In a raw sewage treatment system of the type where-in screened raw sewage includes suspended matter, which is sus-pended in water, in which matter is also dissolved, and floatable matter, wherein the raw sewage is first introduced into a primary settling tank for separating by settling suspended matter, the settled suspended matter being then converted to form fresh ac-tivated carbon and ash material, at least part of which is then mixed with the water derived from the primary settling tank and fed to a secondary settling tank where the fresh activated carbon and ash material adsorbs matter in the secondary settling tank and settles to the bottom of the secondary settling tank as a first slurry, the system being characterized by the absence of aeration means for enabling non-biological digestion of sewage therein, the improvement comprising: means for mixing said first slurry with incoming screened raw sewage prior to its introduction into said primary settling tank; means for transferring said first slurry from said secondary tank to said means for mixing; means for transferring the mixture of screened raw sewage and first slurry from said means for mixing to said primary settling tank whereby the time required for the suspended matter to settle is considerably reduced, and means coupled to said primary settling tank for removing therefrom floatable matter which floats on said water in said primary settling tank, so that the water which is derived from said primary settling tank for mixing with the fresh activated carbon and ash material is substantially free of floa-table matter.

19. In a treatment system as recited in Claim 18 wherein the amount of said first slurry which is transferred to said means for mixing by said means for transferring is suffi-cient to provide an amount of carbon by weight at least equal to the weight of the organic matter in the screened raw sewage.

20. In a treatment system as recited in Claim 18 the improvement further including, means for receiving water from said secondary settling tank after said first slurry had been removed therefrom and for filtering therefrom unsettled carbon particles; and means for adding said unsettled carbon particles to said first slurry.

21. A system as described in Claim 10 wherein said screened raw liquid waste includes floatable matter which floats on said liquid in said first settlement container means and floa-table matter removing means connected to said first settlement container means for removing the floatable matter therefrom.

22. A system as described in Claim 21 wherein said floatable matter removing means extend to said converting means for supplying thereto the removed floatable matter for conversion into part of said fresh activated carbon and ash material.

23. A system as described in Claim 21 wherein there is included filter means; means for applying to said filter means the remainder of said second mixture in said second settlement container means after said used carbon and ash material has set-tled therein to separate therefrom any unsettled carbon particles;
and means for adding said unsettled carbon particles to said used activated carbon and ash material.