US2640807A

US2640807A - Method of waste disposal

Info

Publication number: US2640807A
Application number: US80727A
Authority: US
Inventors: Cyrus W Rice
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-03-10
Filing date: 1949-03-10
Publication date: 1953-06-02
Anticipated expiration: 1970-06-02

Description

June 2, 1953 c, W,I RICE 2,640,807

METHOD OF WASTE DISPOSAL Filed March l0, i949 4 Sheets-Sheet 1 6L-f a [murali il, 7 @TM @wrm .97: L6 @VH1/97 June 2, 1953 c, w, RlcE 2,640,807

METHOD oF WASTE DISPOSAL Filed March 10, 1949 4 Sheets-Sheet 2 June 2, 1953 c. w. RICE METHOD oF WASTE DISPOSAL.

Filed March 1o, 1949 4 Sheets-Sheet 3 [mn To NNN .GNN

Cytaa ldm. J

June 2, 1953 c. w. RICE; 2,640,807

METHOD oF WASTE DISPOSAL Filed March 10, 1949 4 Sheets-Sheet 4 WENTQIQ Cyan -/m ffice Patented June 2, 1953 UNITED STATES PATENT OFFICE METHOD F WASTE DISPOSAL Cyrus W. Rice, Pittsburgh, Pa.

Application March 10, 1949, Serial No. ,80,727

4 Claims. 1

This invention relates to the treatment of acid and cyanide i-ndustrial Wastes.

Acid and cyanide Wastes are formed adjacently in various industrial operations. For example, in the steel industry pickling operations and cyaniding operations are sequentially performed on bodies of metal for plating with nickel, chrome or the application of other protective or ornamental coatings. Wastes containing sulphuric acid or one of the other mineral acids are highly detrimental if present in streams in substantial concentration and Wastes containing cyanides are poisonous to stream life and dangerous to human life if carried into streams in any appreciable quantity. Certainty in operations for disposing of those Wastes is therefore a matter 0f necessity. Certainty in neutralizing the acid wastes and in combining or decomposing'the cyanide Wastes having been assured, efficiency and economy in the methods of disposal are greatly to be desired. Assuming that the reagents as for neutralization and decomposition must be present in quantity in excess of that theoretically required for those reactions, it is desirable to utilize the reagents in as slight excess as gives certainty in disposal. Also it is desirA able, still within the bounds of safety, 'toy lnnimize the number .ofV tanks required for treating the wastes and for settling the products of the treatment.

One object of my invention is to insure com, plete neutralization of the acid Waste and to insure complete decomposition of the cyanide Waste.

Another object of my invention is te provide a system so safeguarded that it is made certain a safe excess of the reagents 'for rendering the wastes harlnless Will at al1 times be supplied, and to minimize the quantity of reagents required for positive safety.

Another object of my invention is to provide simplied plant structure of such sort that it re.- duces the initial cost of plant installation, While also attaining the other objects of my invention relating to the maintenance of assuredly safe conditions with a minimum expenditure of reagents.

Another object of my invention is to provide a system for disposing oi industrial wastes of the type indicated above which is under automatic and correlated control of both the intake of wastes to the system and the supply of requisite reagents thereto to maintain safe conditions, and automatically to safeguard the supply of reagents.

2 It may be stated generally that in attaining the objects of my invention, one course I pursue is to maintain a large body of sludge in the icon-5 ditioning tank for treating the acid waste and in the conditioning tank for treating :the cyanideY waste. Also I maintain a large body of sludge` in a settling tank which is common to both industrial Wastes. The .conditioning tanks are so ar-A ranged that efuent cannot pass from a tank without passing through the body of sludge. In accordance with my preferred procedure, I greatly overtreat the cyanide waste in the cyanide conditioning tank to give lan eiiiuent which contains a relatively high alkalinity. effluent from the cyanide conditioning tank in to the acid conditioning tank and then pass eiiluent from the acid conditioning tank into the common settling tank. In passage through each of these conditioning tanks, the liquid Wastes pass through a large body of sludge and carry some oi the sludge to the settling tank.

In the accompanying drawings illustrative of installation suitable for the practice of my invention:

Fig. I is a diagrammatic ovv plan of a cornplete installation for conducting my method ,of Waste disposal, including electrical means for controlling the sequential steps of the process.

Fig. 'II is a diagrammatic Aplan view showing a.

group of treating tanks arranged as in Fig. I on an enlarged scale.

Fis. III is a diagrammatic primarily vertical sectional View .of the arrangement of treating' tanks shown in Fig. II. y

Fig. `IV :is a diagrammatic; plan view showing one modification in the arrangement of treating tanks.

Fig. V is a diagrammatic primarily vertical sectional View o1' the arrangement of .treating tanks shown in Fig. IV.

Fig. VI is a diagrammatic plan view showing another modication in the arrangement of treating tanks.

Fig. VII is a diagrammatic primarily vertical sectional View of the arrangement of treating tanks shown in Fig.

Referring initially to Figs. I, Il and III of the drawings, reference letter A designates a treating tank for cyanide Waste, reference letter B designates a treating tank i'or acid waste and reference letter C designates a common settling tank for both the treated cyanide Waste and the treated acid waste. Associated with these several treating tanks there is a cyanide collection tank 4 and an acid colection tank 5. It will he I 'pass this assumed that the cyanide is one commonly used in the plating of metal surfaces, such as the highly poisonous sodium or potassium cyanides. It also will be assumed that the acid is one of the corrosive mineral acids used in pickling operations on metals, of which acids sulphuric acid may be taken as typical. The end result of the treatment is, as above explained, so to react wastes containing such substances as to render them innocuous.

As above noted the wastes which are sub-jected to treatment are a cyanide waste and a mineral acid waste. In my process as hereinafter described the more dangerous cyanide waste obtains in addition to its individual treatment the advantage of increased retention as mixed with the more profuse sludge from the treatment of the acid. As described the system comprises individual treating, or conditioning, tanks for each of the two diverse wastes and a settling tank common to both.

It should be understood that the process has greater flexibility than is presented directly in the specific description by which it is illustrated. Thus, the wastes which are treated may be organic as well as inorganic, such for example as acetic acid waste, the Wastes from paper-making, tanning and the like which should not be allowed to pass into streams in unaltered condition, but must be brought into a safe condition f approved by supervisory bodies. Also the wastes from other than industrial processes can be included properly in the treatment. Thus, for example, sewage and other organic refuse may be treated in accordance with the process.

Also, it is possible to conduct the process while individually treating more than two wastes which receive conditioning reagent from a single source; and it is possible to conduct the process while running more than two wastes into a common settling tank. This primarily involves merely duplication of collection tanks, conditioning tanks and controls and the correlation of those apparatus elements and the wastes subjected to treatment into the general operation of the A process.

Also taking the illustrative installation as it stands, it is possible to conduct the process using only one-half of the system up to the settling tank. In so doing there will be full advantage derived from a continuously and instantly available supply of reagent and of the control conditions by which the reagent is supplied as the iiow of the waste to treatment begins, and in which the quantity of such reagent is controlled by desired conditions in the conditioning receptacle in which the waste is subjected to treatment. Insofar as sludge accumulation in the settling tank is concerned, in an operation so conducted such sludge will be supplied by the reactions of the particular waste subjected to treatment, but may be supplemented by sludge derived from previous treatment in the other half of the system or by arbitrary addition of sludges.

As the process is hereinafter described, the employed reagents are given as chlorine and calcium hydroxide solution (milk of lime), as reagents typical for decomposition of the cyanide and the mineral acid. Even in the treatment of those particular wastes calcium hydroxide is given as exemplary of a reagent which releases free hydroxyl ions in water solution and which suitably may be used. In treating wastes of other types other reagents may be more desirable.

As commonly resulting from the cyanide treatment of metals, such as iron and steel, there are two forms of cyanide waste. One such form consists of the cyanide liquor which is discharged from time to time from a cyaniding tank. Such waste is highly concentrated. The other form of cyanide waste consists of the rinse water in which metal from the cyaniding tank has been rinsed, this waste being of course relatively dilute. The same is true with respect to the acid waste, the acid rinse water being presented for disposal in relatively great volume and the concentrated acid waste being presented in relatively small volume. In order that the process may proceed accurately it is necessary in both instances that the dilute rinse Water and concentrated waste be mixed to give uniformity in the concentration of the wastes which are treated. To mix the total drainage of the vat in which metal is treated with either acid waste or cyanide waste with the rinse water at any one time would require an unduly large pit or collection tank for the mixing.

Collection pit, or tank, l: for the cyanide waste contains primarily cyanide rinse water which is brought to the tank by line 6. A tank 'l for concent-rated cyanide waste receives that waste by way of line 8 and delivers it through line 9 to the collection pit, or tank. This line 9 is controlled by valve l0 which opens under the influence of float box ll. Similarly, a line I2 brings acid rinse water to acid collection tank 5, and that tank also receives concentrated acid waste from a tank i3 which receives that Waste by way of a line la and passes it to collection tank 5 by way of a line l5. Line I5 is under the control of a valve i6 operated by a oat box l1. The concent-rated cyanide waste and the concentrated acid waste are bled evenly over the operating period into the cyanide collection tank 4 and acid collection tank 5 under the influence of the respective float boxes Il and l1, each of which is provided with a nlter and a xed measuring orice. A circulating agitator I8 operable under the inuence of a timer I9 is provided to insure uniformity in the composition of the waste liquor in collection tank Ll. It is to be understood that either or both tank 1 for concentrated cyanide waste and tank i3 for concentrated acid waste may be of the portable sort. The manner of proportioning the introduction of concentrated wastes into the dilute wastes with blending avoids the necessity of large capacity tanks in order to insure a waste liquor for treatment which is of uniform concentration and reasonably dilute.

Any of the known reagents suitable for rendering cyanide waste and acid waste innocuous may be used in conducting a treatment in accordance with the method of my invention. Assuming, for example, that the typical reagents chlorine and calcium hydroxide are used, I have found it desirable automatically to prepare a lime solution and to maintain it under such conditions as to render it instantly available.

'I'he organization for supplying lime solution for reaction comprises la storage bin 20 for dryA lime, a lime solution tank 2l and an electrical operating circuit 22 having a push button contro-ller 23. When circuit 22 is energized it operates the motors 24 of twoI cooperative pumps 25 which draw solution from tank 2 l by way of line 26 and also energizes motor 2 la. which actuates an agitator in lime solution tank 2l. Both pumps communicate with a line 21 one branch 2B of which leads to a supply line 29 and the accesos other branch of whichis a recirculating linev 30 returning lime solution` to. tankv 2lI by/way of pressure relief valve 3 1. These DuJnpsl operate continuously during the functioning of the systemto maintainA a constant pressure of the lime solution in lime supply' line 29. A second Yelectrical circuit 32 is energized by a :doet-controlled switch 33 toopen solenoid valve 34' and admit waater to the tank byvway of Water line 3'5. Simultaneously it introduces finely divided' solid lime to the tank from bin 2'@ by the action of an electrica-lly operated measuring feeder 35. This organizationA automatically insures an adequate supply of limel solution at all times. during the functioning of the. system, and by keeping that solutionl continuously under pressureV renders it instantlyuseful.

Assuming that the system is prepared for operation, with a. pressure of' limes solution built up4 in lime' supply line'E-S and exerting pressure on solenoid-controlled

valves

31 and 38 positioned respectivelyy in supply line 29 on opposite sides of its connection with line 28 leading from lime solution tank 2l, andY with cyanide waste and .acid waste in tankv 4 and 5 respectively, the system is4 placed automatically in operation when the liquid level in either or both oi those tanks rises above a prescribed point.

Referring first to collection tank il' forcyanide waste, a Hoet-controlledswitch 3u actsto en ergize electrical circuit 40 and thus to.y initiate a series4 of operations, when' the liouidlevel reaches the point' for which the float is set. Thus, energization oi" circuit' 4l) starts motor 4| which actuates pump H2- drawing cyanide. Waste from tank 4 into cyanide line d3 and. energizes motor 4'4 which actua-tes cooperative draw-oil pump 45. Simultaneously, solenoid valve 3T in lime supply line 29 is opened to permit' lime solution to enter cyanide Une 43'. Also simultaneously, chlorine is pumped' into cyanide line 4'3 pasty pressure :relief valves 46 in lines 4l from chlorine storage tanks 48 by cooperative pumps 49 and` 50 actuated respectively' by motors" 5l" and 52, and a. motor 53 is energized to operatey an agitator` 5f#v (Fig. III) in dovvncomer 55 oicyanide-conditioning tank A. Atthe upper emil of downcomer 55 there is a vertically adiustable funnel 55a the adjustmentf which influences the extent of the -aeration to which the Waste is subjectedv in. ts

treatment.

Itmay be noted that a second' neat-controlled switch.. 56 operated by a float placed at a. higher level than. the iioat of. switch 39V acts to energize the motors of the draw-off pumps and chlorine pumps and to operate solenoid valve 3l in the lime supply line. and the agitato-r of cyanide cond'itioning tank AL. This second switch 5S acts if. for any reason switch 3.9'. should fail' tol `opera-te.

Also operable when the electrical circuit 4U is` energized by either oatfcontrolled switch, there is a pli"` controller 5l communicating electrically withan electrodea and filter-ing. sampler 59, which latter communicates with the. interior of conditioning tank A by. way of. a. duct 60... A switch Si provides for disconnection between the pI-I controller and electrode to provide for changing electrodes. Abyepass connection 52 inlime supplyv line. 29 oy-passing solenoid valve 31,. contains a. solenoid valve 53. to which circuit Ml is completed under the influence of pHk controller 5l.. Valveal remains open. to supply a predetermined quantity oi" the. lime solution for treating the cyanide waste. Valve 6.3 opens. intermittently to admit.y additional. lime-solution to the cyanide 5 line at such timesvastheplivalue of Waste treated. int conditioning tank A'. falls' below aspre-- scribed minimum,

The organization. with respect' to the withdrawal and treatment of acid waste is identical exceptthat no provision ismade for supplying' chlorine to the line conducting acid waste for treatment from acid storage tank 5 to acid conditioning tank B. I-Iere also We have a oatcontrolledswitch 64 and a second switch 65 operated by a flo-at set ai; a higher level, either of which Switches acts to energize electrical circuit 66. Energization of circuit 66'. starts the same general series of operations as previously' described with respect to the cyanide waste, en-

ergizing motors 61 and which operate` pumps 65 and 'Hland drawing on acid waste into acid line H- leading to acid conditioning tank B'. At the same time solenoid valve 35 in lime` supply line 29 isopened to admit lime solution toacid line- 1l. Also motor 'l2 which operates an' agitator 13 (Fig. III) in downcorner lli of acid conditioning tank B iss-energized. At the upper end of downcomer lli there is a vertically adjustable funnel 74a. the adjustment of which inuence's the extent of the aeration to which the waste is subjected to treatment.

Also operable vWhen-'the electric circuitis exierg-ized by either flo-at controlled switch, there isa pH controller l5`communicating electrically with an electrode 'I5 and filtering sampler l1, which latter communicates with the interior or* conditioning tank B by way of a duct 18. A switch le provides'for disconnection between the pIl controller and electrode to provide for changing electrodes. Valve 38 remains open to supply a predetermined quantity of the lime solution for treating the acid waste. A ley-pass connection all in limesupplyfline- 29' ley-passing solenoid valve 33 contains a. solenoid valve 8l to which circuit 66 is completed by' pl-I controller 15. Valve 8| thus.-opensintermittently to admit additional-lime solution to acid line ll at such times as the pI-I value of Waste loeingy treated in conditioning tank B falls below a prescribed minimum.

Cyanide waste entering cyanide conditioning tank A -by wayA of cyanide liney d3' enters downcomerV 55 of' the tank and passes downwardly therethrough, being agitated' in. passage by agitator 54. It is to be understood thatV with this cyanide Waste there is included linie solution entering line L13' by way of lime supply line 2.9 and'. chlorine entering cyanide line All by way of chlorine supply line lll'. In Figs. Il andlII- the position andv arrangement of the linie supply line andthe lchlorine supply line is'simplied to bring those .lines intoA the illustration of' those gures oi the drawings. In passage of the cyanide Waste downwardly in downcomer 5.5 o"v the. cyanideconditioning tank, the` waste is aerated' by air induced ovcr'thelip of tunnel' liliaby the action ofagitator 5ft. In the downcoiner the' reactions which have begun in cyanide line 43 are' continued. and upon issuance of the waste undergoing treatment lfrom. the lower end oi' downcomer 55 intotlie outer chamber 8.2 .of conditioning tankv A, it meets. and is vigorously mixed' witha volume ofv sludge which is allowed to build up at the base of the tank. As the level of liquidI rises. in cyanide conditioningtank A because of aeration and' incoming waste it passes over a' sau/toothed overflow 83 into an annular trough dlfrom which it passes as eiiuent to settling tank C..v This cfiiuentV waste, which is highly aerated',

'carries with it into tank C some of the alkaline sludge with which it is mixed in conditioning tank A.

Acid waste entering acid conditioning tank B by way of acid line 1l enters downcomer lll of the tank and passes downwardly therethrough, being agitated and aerated in passage by agitator 13. It is to be understood that with this acid waste there is included lime solution entering acid line 1i by way of lime supply line 2S. In Figs. II and III the position and arrangement of the lime supply line is simplified to bring that line into the illustration of those figures of the drawings. In passage of the acid waste downwardly in downcomer M of the acid conditioning tank, the reactions which have begun in acid line 'Il are continued. In the downcomer and upon issuance of the waste undergoing treatment from the lower endof downcorner 'l into the outer chamber 85 of acid conditioning tank B it meets and is vigorously mixed with a volume of sludge which is allowed to build up at the base of the tank. As with the cyanide waste, the acid waste is aerated by air which is induced as liquid flows into the downconier over the lip of funnel 'Ma for recirculation. As the level of liquid rises in acid conditioning tank B because of aeration and incoming waste, it passes over a saw-toothed overflow 85 into an annular trough 8l from which this effluent water passes to settling tank C, carrying vwith it some of the alkaline sludge from tank B.

In both conditioning tanks the mixture of waste undergoing treatment and the reagent together with accumulated precipitates is subjected to an aeration which accelerates the treatment. The aeration is effected by induction of air as liquid from the outer chamber of the tank is lifted over the lips of the funnels at the upper ends of the downcomers for recirculation. Thus the level to which a funnel is adjusted controls the volume I" recirculated liquid mixture and the air induced by the recirculating inflow` This intimate blending of the wastes and chemical precipitates accompanied by foaming and recirculation assures an eiectively complete destruction of the original properties of the wastes. When operating in tanks of a size which may be considered normal for full scale operation, the sludge accumulation in the tanks when quiescent should have a depth of several feet.

Line 88 leading from annular trough 84 of cyanide conditioning tank A enters an annular downcomer provided between the wall of inner downcomer 89 and an outer shell 96 in settling tank C. Passing downwardly through this annular space to its opening in the lower region of tank C, cyanide waste enters a body of sludge carried over from both the cyanide and acid conditioning tanks, or formed by completion of the reactions in the settling tank. Eiiiuent from annular trough 81 of acid conditioning tank B passes by way of line 9| to a space ywithin the inner downcomer 89 of settling tank C and passing downwardly through this downcomer also enters the body of sludge collected in the bottom of the tank. A motor 92 rotates a shaft 93 which carries blades 93a positioned below the lower ends of the downcoiners. Such blades are rotated very slowly merely to produce some movement in the sludge toward the center of the tank and thus to facilitate its intermittent Withdrawal from the tank. As the level of liquid in cuter chamber 94 of settling tank C rises with continued operation oi the system, it passes over the saw-toothed overiiow 95 into an annular sump 96 from which it ilows as harmless effluent by way of a draw-off line 91.'

At the base of conditioning tanks A and B and settling tank C there are respectively valved draw-off

lines

98, 99 and |09 which may be used to maintain a suitable level of sludge in the several tanks. If the character of the sludge in cyanide conditioning tank A should be questioned, such sludge can be corrected with sludge from acid conditioning tank B before its transfer to settling tank C to become part of the mixed sludge at the base of that tank. Also, if desired, sludge may be transferred from settling tank C to supplement the sludge precipitated in either of the conditioning tanks A and B or sludge from one of those tanks can be transferred to the other of said tanks to supplement the sludge formed therein. In practice the discharged sludge is collected in tank trucks and delivered to a dump.

The reactions involved in rendering the specifically indicated wastes harmless will now be described. As cyanide waste is taken from the cyanide collection tank and fiows through the cyanide pump-line to cyanide conditioning tank A, it receives in passage a charge of calcium hydroxide and of chlorine, carrying these reagents with it into the downcomer of the cyanide tank and being thoroughly mixed with the reagents by agitation in the tank. The reactions begin in the cyanide line and continue into the cyanide conditioning tank. As the reactions take place, reaction products are precipitated to form the sludge in the cyanide conditioning tank. These reactions may be illustrated as follows:

This reaction takes place very rapidly and by it the intensely poisonous cyanide is converted to the relatively harmless cyanate.

Although these cyanates such as sodium cyanate and potassium cyanate have only about IAOOO the toxicity of the corresponding cyanides, the cyanate is itself destroyed by continued reaction with an alkali and chlorine as in accordance with the illustrative formula:

The iirst reaction given above, which is the reaction vprimarily effective in `destroying the toxic properties of the cyanide Waste, is substantially complete within about one or two minutes under conditions of alkalinity exceeding a pH of 8.5. The second reaction takes place within an hour. These are accepted reactions in accord- -ance `with literature references. The actual operation of the method as herein disclosed was checked under pilot plant conditions. Under those conditions the results indicated that the rst reaction was complete Within one minute on waste having an initial 100 p. p. m. cyanide concentration. The second reaction was about 80% complete within two hours and the toxicity of the cyanate being relatively so low the reactions were considered in practical effect completely to have destroyed the toxicity of the cyan1de lwaste. During the test of alkalinity in the cyanide conditioning tank it was maintained at a pH of about 8.7. During the operation of the process as conducted the pHin the cyanide conditioning chamber is therefore to be understood as maintained in excess of a pH of 8.5.

.Assurance of adequate treatment of the cyanide waste in its conditioning tank is assured by mixing the reacting waste with a considerable body of the sludge precipitated in the tank. l'

aardse? The treatment fof the acid'lwaste is 1close1y similar. Acid waste vtrom -tlre -acid collection -tank :or pump-pit in its passa-ge top-'acid conditioning tank l5; receives a charge of lime solution with which it enters the downeomer of the tank and is thoroughly mixed for 4reaction 'with the lime solution during passage through the-down vcomer-to the lower region'o'f the tank. The vpri- 'mary'reaction isone ofthe wellknown neutralizing reactions, such as:

Mixed lwith the precipitated CaSOi there are precipitatesof metal hydroxides such as 'the-hydroxides of iron, nickel andchromelgo'ing to fforrn the `sludge `in `the'lower regionvof'fthe acid conditioning tank. 4In this 'tank vthe alkalinity is maintained at a -pH inlexcess lof fr, such as "a pH of 7.5 andhigher.

During 4the `operation of 'the method, flow of llime solution to both the cyanide conditioning tank and -the acid conditioning -tank yis jquantita- 'tively under the control of p-I controllers v5l fand "V5 'the passage or Achlorine to the cyanide conditioning tank being regulated "by 'the setting of `Valve '56. Whereas the introduction of the llime solution is proportioned'according 'to the pH, 'the introduction of chlorine is kcontinuous under the 'action of motors 51 and l'52 on pumps il@ 'and forcing chlorine :from tanks 48 past valves d'6. The great advantage of placing the ilow lofi-lime 'under the'influence of 'the pH controllers is twotold. From one .aspect `it'assures that there vbe sufficient 'alkalinity 'in the conditioning 'tanks 'to carry out the necessary reactions therein. From another viewpoint -it assures 'that the necessary results be obtained with a minimum ofthe reagents whichrender'the wastes harmless; it 'being `imderstoodfthat the vmaintenance ofproper alkavlinity in the cyanide conditioning tank assures vcomplete utilization of the chlorine Whichis pro- 'Vided and lthus additionally limits .the excess of .are rendered wholly innocuous. The lpresence' V of the substantial `bodies lof .slu'dges rin the two Aconditioning tanks and in the .common settling .tank 4fullyprotects the system against 4slugs #of wastes having a higher than normal concentration of toxic components. ance of slugs is guarded against 'initially by the dolending or concentrated Wastes from 'actual Ypickling and cleansing 'operations with the wash waters "from those operations, it is possible that there fmay 'be vsome temporary or localized increase in the concentration of the ytoxic ingredients and -against such conditions the vpassage of wastes undergoing treatment through thesludges "gives Aprotection without ymaintaining .an exorbitantly great excess o'f .reagents in the system. Because of the .fact that the system is under automatic control the possibility `of --difculties rising vfrom human errors and omissions iis Treduced mto a minmum.

Although the 'avoid- A valved return line lili of trough 9S #of` the settling tank leads 4to pumps and 50 ywhich Vforce chlorine from tanks and. past Valves lf3 rication resides in the arrangement of fthe two vconditioning tanks andthe settling tank and the alteration of the sequence of steps-so caused. The

'modified course followed by thewastes in 4accordance with this Variant ci' the process is illustrated `by the arrangement oicyanide conditioning tank D, acid-conditioning tank E and 'settling tank'F which correspond in structure though not -in'arrangement to the analogous tanks A, vE, and@` as previously described.

"Thus 'as shown in Figs. 1V and V cyanide line 'd3 leads todowncom'er E62 in cyanide conditioning tank-D, the connection of lime supply line 29 and chlorine supply line il to this tank being similar to like connections to cyanideconditioning tank A. Similarly an agitator |633 is mounted in downcomer lili hai/ing a vertically-adjustable funnel Etta at its upper end and thedowncomer empties adjacent the lower region of the tank into the bottom and outer chamber IEM of 'the tank. A valveddraw-ci line H5 for "sludge is provided at the base of the tank. Similarly to cyanide'conditioning tank yiik, tank D isequinp'e'd with a saw-toothed overflow H35 over 'which treated water passes into annular trough "I- 'when 'the level of liquid rises'sulciently'in ithe tank. Similarly to cyanideconditioning tank A, cyanide conditioning tank D is equipped witha 4pHvcontroller 'ii inelectrical control circuit-40. The pH controllercommunicatesfelectricallywith `an electrode LIB 'and *filtering sampler liiwhich latter communicates with 'the interior of lconditioning tank D by way of a'duct Nil. A switch iH l provides for a-disconnection between th'epH controller andfthe'elec'trode-to provide for chang- Ving electrodes. Instead of passing directly to Aa. settling tank, however, draw-0H line |12 f1-oni .annular trough -iili of the vcyanide `conditioning tank empties-into dcwncomer ||3 of acidconditioning tank E.

Thistank similarly is equipped with agitator |`|4"indownccmer N3, vertically adjustable funrnel i3d at lthe upper lend of the downc'omer,

-valved draw-offline for sludge I5, `a'saw-toothed overflow i-'l at the upperend of outer chamber lf'll' of the tank from 'which the upper'levelof liquid passes into annular vtrough Hl). `Italso similarly equipped with pH controller Iii-9, :electrode |129, altering sampleriti and-'disconnecting switch |22. The plelicontrolleris incommunica- -ti'on with `the general electrical control 'circuit 66 'of the system. Line *H conducts acid'wastes Aand lime solution to downconier `H3 to meet treated lcyanide5wastefdelivered 'by `draw-'onf line "I f2 *from fcyanideconditioning ltank D.

nro-m .the annular trough iis of acid condi- .fti'oning tank E a draw-off line |23 .leads 'to 'the downcomer 121i! of settling "tankE -tSettlin'g tank tE iissimilarmoonstructioirtofsettling'tarik Cprej- Wiouslydescribed. iikes'ettlingtankC it 'has 'a `wah/'eti tiraweoif connection :|125 y'for 'excess 'sludge and an agitator 26 which is slowly motor driven to move sludge by means oi blades iEEa toward the center of the tank at its base. Settling tank E also has in its upper region a saw-toothed overilow |21 over which the upper level of liquid in the outer chamber |28 of the tank flows into annular trough |29. A draw-oli line |3 withdraws eiiluent from trough |23. It is to be understood that a second valved line similar to the valved return line shown in I can be provided either as independently connected with trough |23 or as a branch of draw-off connection |30 to recirculate eluent through chlorine pumps 49 and 5i) and storage tanks 43. into cyanide line 43 leading to cyanide conditioning tank D,

The modincation of the method as illustrated by the apparatus arrangement suitable for its practice shown in Figs. IV and V of the drawings is preferred procedure. In conducting this variant of the method the pH controller associated with the cyanide conditioning tank is set to maintain a high excess alkalinity in that tank to the extent of maintaining a pH of ll or even higher. This places the emphasis of the process on the destruction of the highly toxic cyanide waste which receives initially a very great overtreatment. The excess alkalinity from this overtreatment serves to treat the acid waste in the acid conditioning tank. Because the reactions by 4which the initial cyanide content of the cyanide waste is destroyed are irreversible this can be done with complete safety insofar as the cyanide waste is concerned. As additional assurance, however, that the wastes oi both types will be rendered innocuous the pH controller of acid conditioning tank E maintains in the acid conditioning tank `an alkalinity, such as is indicated .by a pH in excess of 7.5, adequate to insure complete treatment of the acid waste as well as the cyanide waste. As in the practice previously described this is done by introducing an alkaline reagent such as lime solution into the acid line leading to tank E at such times as the pI-I in the tank tends to drop.

It will be noted that in this modication of the process, also, wastes of both kinds pass to a common settling tank before being discharged as eiu- `ent. Thus in this modication, also, both wastes undergoing treatment are mixed at least twice with bodies of alkaline sludge in the several tanks andthe cyanide waste is mixed three times with sludge before being discharged as eliluent. As explained above, this repeated mixture with sludge insures against the inclusion of imperfectly treated waste in the ultimate effluent under abnormal conditions in which slugs of increased vconcentration pass through the system. With respect to the dangerous cyanide wastes this modiication also provides a sludge admixture addition to that provided by practice of the method as illustrated in Figs. I to III of the drawings. As in the procedure applicable to Figs. I to III, the use of a settling tank common to the wastes of both kinds insures an adequate volume of sludge in the final tank of the system and gives to the dangerous cyanide `waste the advantage of nal treatment in a body of sludge to the formation of which the precipitation of products from treatment of the acid waste has contributed.

The method as conducted in accordance with the procedure illustrated in Figs. VI and VII is identical with the method as described in connection with Figs. IV and V of the drawings. The only diierence involved in the showing of Figs. VI and V11 is in the telescoping of apparatus to simplify the installation in which the 12 plant space required for installation. Here again it is to be understood that all the elements and controls associated with the conditioning and settling tanks as shown in Fig. I of the drawings are present in an installation having the arrangement of conditioning and settling tanks shown in Figs. VI and VII.

Referring to the apparatus as shown in Figs. VI and VII of the drawings, this apparatus comprises a cyanide conditioning tank G, an acid conditioning tank H and a settling tank I, the acid conditioning tank H being arranged within settling tank I. Thus cyanide conditioning tank G comprises a dcwncomer |3| equipped with a vertically adjustable funnel |3|a at its upper end and with a motor driven agitator |32 and a valved draw-off line for sludge |33. Cyanide line 43 in communication with lime supply line 29 and chlorine line 41 opens into the upper end of downcomer |3I. Similarly to the analogous tanks which previously have been `described cyanide conditioning tank G is shown as provided with a saw-toothed overflow |34 over which liquid rising in the outer chamber |35 of the tank passes into annular trough |36.

The combination of acid conditioning tank H and settling tank I comprises a downcomer |31 having a vertically adjustable funnel at its upper end into which discharges draw-off line |38 for eiiluent from the cyanide conditioning tank. Acid line 1|, to which connection with lime supply line 29 is shown, also discharges into downcomer |31. In downcomer |31 there is a motordriven agitator |33 and at its lower end the downcomer opens into a downwardly closed receptacle which serves as the acid conditioning tank H. Surrounding downcomer |31 there is a bailie sleeve |40 which extends to the upper end of the tank and surrounding acid conditioning tank H there is a second baiiie sleeve |4| which also extends to the upper end of the tank. It will be noted that the upper and receiving end of downcomer |31 lies above the upper end of the acid conditioning tank H and is equipped with vertically adjustable funnel |31a. In the upper region of the settling tank I in the outer chamber |42 thereof and surrounding outer baffle sleeve |4| there is a saw-toothed overiiow |43 over which the upper level of liquid in the settling tank can flow into annular trough |44. A draworf line |45 receives eiluent from trough |44 and it will be understood that a return line for conveying eiiluent to the chlorine pumps desirably also is provided as shown in Fig. I of the drawings and as above discussed. Similarly to the conditiomng tanks as previously disclosed a pH controller is associated with cyanide conditioning tank G and with acid conditioning tank H standing within settling tank I. Thus, as shown, cyanide conditioning tank G has associated therewith a pH controller |46 in communication with electrical control circuit 40 and with an electrode |41 and a filtering sampler |48 communicating with the interior of the tank. A switch |49 provides for disconnection between the pl-I controller and electrode to provide for changing electrodes. Similarly acid conditioning tank H has associated therewith a like organization of pI-I controller |50 in communication with electrical control circuit 66, an electrode |5|, a ltering sampler |52 and switch |53 for changing electrodes.

Cyanide waste entering cyanide conditioning tank G is treated identically as in cyanide conditioning tank D shown in the apparatus organization of Figs. IV and V, excess alkalinity to the extent represented by a pH-off 11 or over beagecogcor ing Vmaintained in the tank. -Eiuent from 'the Ycyanide conditioning tank passing into downcomer -l 31 in the acid "conditioning tank and settling tankassembly meets -With acid "Waste and isthoroughly mixed v.Within the acidconditioning tank, the-excess alkalinity of Ethe'cyanide waste undergoing treatment providing :neutralizing reagent for the acid Waste. As in acid conditioning tank `E of Figs. lV-and V, the pHcontroll'er of acid -conditioning t'ank-il-Iv 'serves' tomain'tainralkalinityfata Vsuitable 'Value in excess fof 7*.5 lin the acid conditioning tank.

As the level of-liquidinthefdowhwardlylclosed acid conditioning tank 'rises, that liquid hows over the lip of vthe tankinto "the annular vspace between the 'wall of .the ltank and outer baliies fili and downwardlyinthat space tothe bottom and'outer chamber'ofsettling tankl. Underth'e inuenc'e 'of `agitator 139 4sludge 'also is carried over the lip of acid'conditioning tank Hand'into the 'settling tank I. When settling 'tank 'I :has lined, `the liquid whichfas in other' variants 'of my process consists of Aclear .and harmless water, flows oversaw-toothed overow M3 into annular trough M4 and -is discharged .as Yeilluent .through line |45 or is recirculated back Ato the chlorine pumps. It should be noted that sludge as Well aslq'uid is'carried over the lipfof acid conditioning tankl-I and passes to the bottom 'of settling tank I. A suitable .level of sludge yin thefsettling .o

tank is maintained by drawing-off sludge from .time to time by Way of valved discharge line 154. It is thus clear that lthe conduct of the method in the organization of Figs. VI and lVII is identical with the method as conducted vin the apparatus of Figs. IV and V.

:Considering the process purely :as a Achemical process apart from the disclosed automatic controls, it consists in separately treating two di- -verse wastes, one'of which is .more toxic than the other and both of which originate in the lform both 7Vof concentrated Waste 'and dilute waste. In preparation for-reaction these Wasteseachai'e blended by a continuous operation, `toobtain-uniformity of vdilution under condition'scso Ycontrolled that the likelihood of deliver-y of la -waste in .its more concentrated form lfor :reaction is minimized. As each of the Wastes in its blended form hows to treatment it 'is charged with a reagent, or reagents, appropriate for reactions which render the waste innocuous. These nblended and charged 'wastes are then treated separately with repeated agitation and aeration in admixture with sludge, which sludge typically is composed of the products Vof the reaction 'by which the wastes aredecomposed and contains an'exc'ess of the decomposing reagent. After reaction 4With agitation and aeration for a period suiicient under normal circumstances to lrender the Wastes harmless, they both pass as eliiuerit to a'commo'n settling receptacle in which the effluents mix with a body of sludge'in'thesettling receptacle and remain .for a further retention period under `conditions 4in which there is an `eacessvof the Adecomposing reagent, until they iinally Dass as a common and harmless eluent from the settling tank.

As a preferred modication of this process, there beine; a reagent appropriate to the treatment of both the said Wastes, the more ltoxic of the two wastes is treated with a great excess of the common reagent. The effluent from this Waste then carries an excess of that common reagent to a receptacle in which such excess is employed in treating the second Waste. In this reaction additional reagent is supplied if necessary in order to assure complete decomposition of Cil lili both wastes `line 'combined Ysituent thenfpasses from the second receptacle-'to la'sttling receptacle for fur-ther retention .and ultimate discharge.

Considered llfrom the 'viewpoint of automatic control'as 'Well as of purely chemical process, a supply of -the reagent which :is common toit-he Wastes of -bo'th ity-'pes is mai-ntainedunder con- -stan't ipressure for instantaneous addition to the 'Wastes in their passage vto treatment. Addition of this common reagent is made `lauto'matically and instantaneously under 'the 'influence lof the electrical controls 'which initiate -owio the wastes to their individual treatments. lIn .conjunction -lW'ith the initial blending of eachof the 'Wastes v'with vrespect Ito its `concentrated ian-'d `dilute occurrence, thislinstant supply of reagent prevents `lthe passage 'oi vslugs of Vraw lwaste Jto vtreating receptaclesfapart-from'the reagent 'with Vwhich that Wasteis to be reacted. Further controls 'automatically Y supply such quantity "of the additional reagent vaslmay be required vtomaintain conditions appropriate to the cornplete decompositionv of the 'two wastes in their .initial treatment. 'These .controls are 'suchastom'aintainnexces's of reagent in eilluent lfr'omthe .initial 'treatments passingto the common `settling container.

It will be understood that it may be desirable even though there befonly 'one 'particular Waste to be subjected-to treatmentthatth'esupply .of suchwa'ste `loe dividedffor initialftreatment, ibut that the yetfluen't's from the 'initial 'treatments lloe brought together for a lcomm-'on settling `,xreriod before an ultimateeiuentis discharged. .Also that any number of diverse Wastes initially treated may be brought "to a vc'orr'irnon settling tank and maintained under such chemical conditions as give additional assurance as to 'the harmless nature of the comldined effluent. In either case,orfi`f an individual wasteis lsimpl-y to be treated by itself-as in one-halfentheltreating system, the automatic blending is of importance when the Wasteoccurs'both in concentratediand dilute form. Also -suchblendingmay userully be practiced on unlike wastes both-of Which-canbe 4completely treated yby 'a "common reagent and one "of which is *of 'such nature Ytha'jt `blending with the other bef-oretreatmentis"advantageous, 'n'any 'event 'automatic Icontrol byiv'vhich reagent "in sudcient quantity is supplied inac'cordance with 'the condition of the waste undergoing 'treatment isan importanteature.

Icla'iin as"my invention:

v1; The method of treating'two 'Waste Waters l`from industrial operations v4which 'waters respectively contain .in 'solution diverse toxic sub- Xsta'nces, the said dissolved'substance in one'sa'id water exceedi*ng thatoftne'uth'erwaterfin'toxiaity, "the reactions "for rendering which 4toxic substances 'harmless involving at least one `common reagent, by v Hot/ing .the Said `S`1lt0h`svlfb`m volumes of .supply thereof "to reaction chambers `therefor, 'throughout the iiow of said "solutions Asupplying to each thereof reactive material containing the common reagent capable of rendering the toxic substance of the said solution harmless by reaction therewith, the amount of reaction material added being suicient to supply a substantial excess of said common reagent to the solution containing the toxic substance of 4greater toxicity, owing eiiluent containing excess of the said common reagent from the reaction chamber for the solution having a toxic conjtent of greater toxicity into the reaction chamber for the solution having the toxic content of lesser toxicity, and following reaction in said last named reaction chamber settling the mixed reacted solutions and the solid products of reaction therein and drawing off eiuent therefrom.

2. The method of treating two waste waters from industrial operations which waters respectively contain in solution a mineral acid and a cyanide, the reactions for rendering which toxic substances harmless involving as a common reagent a substance capable of supplying free hydroxyl ions in Water solution by owing the said solutions from volumes 0f supply thereof to reaction chambers therefor, throughout the flow of .said solutions supplying to each thereof reactive material capable yof rendering the toxic substance of the said solution harmless by reaction therewith, the said hydroxyl ion supplying substance being added to both said solutions and chlorine being additionally supplied to the said cyanide solution, the said hydroxyl ion supplying substance as a common reagent lbeing added in substantial excess to the solution containing cyanide, iiowing eliiuent containing excess of the said common reagent from the reaction chamber for the cyanide solution into the reaction chamber for the mineral acid solution, and following reaction in said last named reaction chamber settling the mixed reacted solutions and the solid products of reaction therein and drawing off eiiiuent therefrom.

3. The method of treating two waste waters from industrial operations which waters respectively contain in solution diverse toxic substances the said dissolved substance in one Said water exceeding that of the other said water in toxicity, the reactions for rendering which toxic substances harmless involving at least one common reagent, at least one of said waste waters occurring in the form of a relatively dilute and a relatively concentrated solution of the toxic substance therein, in the receptacle containing a volume of supply of the said dilute solution automatically iiowing off suicient solution from the volume of supply to a reaction chamber on inflow of the more dilute solution to maintain a constant level of solution in the receptacle containing said volume of supply, continuously making a blend of the said more dilute and concentrated solutions by bleeding the more concentrated solution of the said toxic substance into the more dilute solution thereof during flow from the said volume of supply, flowing the said diverse solutions each to a reaction chambertherefor, throughout the flow of said solutions automatically supplying to each thereof reactive material, containing the common reagent, capable of rendering the toxic substance 0f the said solution harmless by reaction therewith, the amount of reaction material added being suicient to supply a substantial excess of said common reagent to the solution containing the toxic substance of greater toxicity, flowing eiiiuent containing excess of the said common reagent from the reaction chamber for the solution having a toxic content of greater toxicity into the reaction chamber for the solution having the toxic content of lesser toxicity, and following reaction in said last named reaction chamber settling the mixed reacted solutions and the solid products of reaction therein and drawing oii effluent therefrom.

4. The method of treating two waste waters from industrial operations which waters respectively contain in solution a mineral acid and a cyanide, the reactions for rendering which toxic substances harmless involving as a common reagent a substance capable of supplying free hydroxyl ions in water solution, at least one of said waste waters occurring in the form of a relatively dilute and a relatively concentrated solution of the toxic substance therein, in the receptacle containing a volume of supply of the said dilute solution automatically flowing off sufiicient solution from the volume of supply to a reaction chamber on inflow of the more dilute solution to maintain a constant level of solution in the receptacle containing said volume of supply, continuously making a, blend of the said more dilute and more concentrated solutions by blending the more concentrated solution of the said toxic substance into the more dilute solution thereof during flow from the said volume of supply, flowing the said diverse solutions each to a reaction chamber therefor, throughout the flow of said solutions supplying to each thereof reactive substance capable of rendering the toxic substance of the said solution harmless by reaction therewith, the said hydroxyl ion supplying substance being supplied to both said solutions and chlorine is additionally suppliedto the said cyanide solution, the said hydroxyl ion supplying substance as a common reagent being added in substantial excess to the solution containing cyanide, owing eiiluent containing excess of the said common reagent from the reaction chamber for the cyanide solution into the reaction chamber for the mineral acid solution and following reaction in said last named reaction chamber settling the mixed reacted solutions and the solid products of reaction therein and drawing oi eiuent therefrom.

CYRUS WM. RICE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,194,933 Barber Aug. 15, 1916 1,418,013 Newman May 30, 1922 1,824,935 Travers Sept. 29, 1931 1,928,163 Barnard Sept. 26, 1933 2,194,438 Wernlund et al Mar. 19, 1940 2,348,124 Green May 2, 1944 FOREIGN PATENTS Number Country Date 538,929 Great Britain Aug. 21, 1941

Claims

1. THE METHOD OF TREATING TWO WASTE WATERS FROM INDUSTRIAL OPERATIONS WHICH WATERS RESPECTIVELY CONTAIN IN SOLUTION DIVERSE TOXIC SUBSTANCES, THE SAID DISSOLVED SUBSTANCE IN ONE SAID WATER EXCEEDING THAT OF THE OTHER WATER IN TOXICITY, THE REACTIONS FOR RENDERING WHICH TOXIC SUBSTANCES HARMLESS INVOLVING AT LEAST ONE COMMON REAGENT, BY FLOWING THE SAID SOLUTIONS FROM VOLUMES OF SUPPLY THEREOF TO REACTION CHAMBERS THEREFOR, THROUGHOUT THE FLOW OF SAID SOLUTIONS SUPPLYING TO EACH THEREOF REACTIVE MATERIAL CONTAINING THE COMMON REAGENT CAPABLE OF RENDERING THE TOXIC SUBSTANCE OF THE SAID SOLUTION HARMLESS BY REACTION THEREWITH, THE AMOUNT OF REACTION MATERIAL ADDED BEING SUFFICIENT TO SUPPLY A SUBSTANTIAL EXCESS OF SAID COMMON REAGENT TO THE SOLUTION CONTAINING THE TOXIC SUBSTANCE OF GREATER TOXICITY, FLOWING EFFLUENT CONTAINING EXCESS OF THE SAID COMMON REAGENT FROM THE REACTION CHAMBER FOR THE SOLUTION HAVING A TOXIC CON-