CA1062447A - Elimination of odors from organic wastes - Google Patents

Abstract

Abstract of Disclosure A method and solution are provided for reduc-ing air-polluting odors emanating from organic waste products produced by metabolic processes and from organic industrial waste including effluents. The method comprises contacting said wastes with an aqueous acid solution con-taining a water-soluble oxidizing agent selected from the group consisting of nitrates, chlorates and permanganates of ammonia and alkali metals, and also a precipitating agent selected from the group consisting of water soluble ferric and ferrous compounds.

Description

` ` 447' ` This invention relates to a novel solution and ,~
~- method for reducing air-polluting odors which emanate from organic waste products, including organic waste products in storage subject to chemical or microbial degradation.
State of the Art , . .
Methods have been proposed for eliminating odors from organic waste products. However, such methods have - not been wholly successful~ For example, in the treatment of human wastes, sanitary products, solids or sanitary 0 fluids have been used. Their main objective is to provide a bacteriostat~c effect. In general, they act as deodor-izer~. Actually, they provide an odor--masking effect ~y employing such aromatics as phenolic compounds, camphor, iso-bornyl acetate, and so foxth, the effect being generally . ., ~15 temporary.
Different methods have been proposed for reducing ~1, the odor o animal waste products in the field where, for example, manure is spread. It has been suggested to aerate animal wastes~on a ~arge scale; however, aeration has not been satisfactory due to the low threshold values of cer-tain of the more odorous compounds. The ~hxeshold values , ox minimum identifiable odor (M.IØ) for mercaptans in `
mg/l in air range between 10 to 3xlO ; for dialkylsul- `
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` ~o6;~47' fides from about 10 to 2.5xlO ; for hydrogen sulfide about 10 and for skatole about 1.2xlO mg/l in aix.
Another method which has been proposed utilises î the deep-level injection of liquia or liquified manure into the soil. This method diminishes odors in the sur-. . ~
rounding ~ields but not in the breeding areas. In Sweden, ~' the foregoing was applied to the abatement of odors due to animal was~es on pig breeding farms. ;~
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The best results, though still not wholly satis-factory, have been obtained with the use of ammonium persulfate. While unrealistically high amounts of this chemical have been used, they still did not eliminate or , reduce the odor entirely. Moreover, the chemical does not .. ~ . ... . .
~ attack sulfur-bearing chemicals. The effect of ammonium ;;
,., ~ ., persulfate has been studied by others, the observations ~ being that while the odor intensity was reduced, it was still .. ~ , ., :
~ not satisfactory.
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~ So ~ar, there has been no satisfactory proposals `'~
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for abating bad odors from organic industrial wastes, no~ `
~; 20 even from sludge derived from sewage works. For example, ~i '; il ~ ~ .
~j an attempt to~mask the odor of sevage sludge similarly met with failure.
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i~ Many organic was~s are produced daily in large ,~ quantities, for example, in large scale animal breeding ~; ;

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` arms, as effluents from the food industry, waste products , rom slaughterhouses, sewage and sewage sludge, among .. others~ In ~hese situations, the bad odor is regarded as a public nuisance and as a health hazard, particularly in the situation where waote products are stored for a ~- relatively long period of time, for example, manure and certain soil improving products. ~ .
~ Obiects of the Inventio~
.~ It is thus the object of the invention to pro~
vide an odor removing or odor abating solution using - chemicals which are not generally harmful to the environ-. "~
.1' ment and which do not substantially adversely affect chemical or biological processes usually applied in the ~'1. . further treatment of organic waste products. ~.
15 ~ Another object of the invention is to provide a method for the ecological recycling of organic waste products without the attendant disadvantages of bad odors.
.In accordance with these objects, the present invention is directed to the txeatment of human and animal waste products arising out of metabolic processes, as welI as to the treatment of organic industrial wastes and 7:?~l, ef~luents.

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~:,~,,. : ' ,i~ ~ .~ . ., .' ' . ~A , `` 1062~47 Stating it broadly, one aspect of the invention i8 directed to a method o reducing air polluting odors emanating from a solids-.~ ., containing organic waste product selected from the group consistlng of , organic waste products produced by metabolic processes including animal~'; and human wastes, organic industrial wastes and sewage sludges which com-prises: contacting said organic waste product with an effective odor-abating amount of an aqueous acid solution con~aining an oxidizing agent .i, selected from the group consisting of water-soluble persulfates, nitrates, chlorates and permanganates of ammonium ion and alkali metals in an .
~' 10 amount sufficient to provide between about 8 and 68 mg 02/g of solution, . a precipitating agent selected from the group consisting of water-soluble ferrous and ferric compounds in an amount sufficient to provide between about 28 and 70 mg Fe/g of solution, and about 3 to 25~ by weight of sulfuric acid; and maintaining said contact until said odor has been substantially removed.
The use of the foregoing solution results in simultaneous ~I reactions involving the acidification and oxidation of the waste and ~;i/ also in the precipitation of odorless and lnsoluble sulfides. The ~Y~
chemicals selected are those which have sufficient solubility in cold water and which are substantially harmless to the surrounding environment.
The reactants employed include substantially all acids, the inorganic acids being the most efficient, e.g. sulfuric acid, Acid salts may be employed, such as peroxidisulfates ~persulfates~, hydrogen sulfates, ferric chlor-lde, and the like. The amount of acid material employed ; should be such ~' - 106Z44t7 ~ . .
,; as to assure a pH of less than 5, and preferably less ~; than 4, in the waste product treated. If the pH rises during treatment, more acid may be added. Examples of efficient odor-removing oxidizing agents include soluble persulfates, soluble chlorates, soluble nitrates, soluble . :
pexmanganates and ferric chloride.
In order to transform such odor-producing chemicals as hydrogen sulfide and organic sul~ur compounds into preci-pitates, water soluble ixon salts are used, with ferrous .;, ~ 10 sulfate and ferric chloride being the most efficient.
, Each rPactant must be present to achieve the ~ xesults of the invention. For example, neither acidifica-;,l tion alone, nor oxidation alone, nor sulfide precipitation '~ alone will adequately remove odors. Successul results are ii 15 obtained when all three reactants are employed together.

!;,.',i,l Complete analysis of odorous compounds derived from organic wastes are not available in the literature.
~!` The type, as well as the amount of odor-forming compounds, ~`, . i8 dependent on the origin of the organic wastes and the 20 ~ conditions and time~of storage. The foregoing consider-ably influence the formation of odorous degradation pro-ducts.
Empirically, I have observed some chemical pro-perties to be typical of certain types of organic wastes.
For example, proteinic wastes, containing relatively more .~ ~ . .

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:.," ,' ~' ~-`` 1062447 sulfur and nitrogen, develop more odorous compounds and more amm~nia. This is particularly true of organic ~astes produced by metabolic processes. These wastes contain urea which soon becomes degraded by enzymes to form am-monia, among other by-products~
The chemical demand for certain wastes for the removal of odors is summarized, by way of example, as follows.
... ' Human wastesare treated with about 50 to 100 mg -~
- ;~' . '-oxygen~kg of waste (850-950 ml); and animal wastes with ~ -about 190 to 205 mg oxygen/liter of waste. As regards organic industrial wastes, average figures are not avail-able as such wastes tend to vary in composition~ The chemlcal demand for sewage normally ranges from about 8 to 10 mg oxygen/l, while sewage sludge (e.g. excess sludge) I requires about 17 to 21 mg of oxygen/l (liter). ;
!~ With regard to the use of iron salts as preci- ~
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pitation agents, for human wastes, about 112 to 180 mg Fe/Xg (850-950 ml) of waste is normally required; for animal wastes, about 150 to 200 mg Fe/l; for sewage, about 30 to~ 35 mg Fe~l; and ~or æewage sludges, about 12 to 30 .
I m~ Fe!1.
~1 ~¦ The acid ùemand expressed in terms of sulfuric acid comprises the following: human wastes, about 3.35 to 3.37 grams/Kg (850-950 ml) of waste; for animal wastes, I~ about 7.9 to 13 grams/l; for sewage, about 0.23 to 0.30 ., ~ ' '.,.~:
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gram/l; and for sewage sludges, about 0.13 to 0O17 gram/l............ ',.
, The foregoing requirements are met by odor~
removing aqueous compositions containing the following am~unts of reactants based on mg/gram of solution as '-~ . , applied to certain wastes~
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~: . - SOLUTION COMPOSIOIO~
Acid ~umber ,~ .
: Type of Waste mgO2/g mg KOH/g* mg Fe/g . _ ~,.,~
Human Wastes 8.6-14 097 2-194.5 28-56 ,' : ~- . ., I i~ .
~nlmal Wastes 56.0-68.0 57.0-69.0 50-60 Sewaqe 40 0-41.0: ~-45 0-46 0 60 :'';
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~:~ Sewaqe Sludqes 28.0-35.0 45.0-237.0 50-70 ¦'~
~:~ * -- The acid is determined by the amount of '15 KOH required to neutralize the acid in . ~' ' soIution, .
..
In certain cases, further acid may be added to ,' :the~waste~product following treatment with ,the odor-removinglcompositions. ~ ':
20~ ' Organic waste products containing phosphates, such as in excess sludge from post-pxècipltation sewage treat- ,~ ' i .
ment systems, may be treated with solutions containing ~",, ' . sufficièntly~hi~h ferrous'or ferric compounds to effect ',~
removal of the phosphorous by precipitation as well as ~' ',.
~:25 removal of the odor.

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: ~ ' 06Z~47 The ollowing are examples of waste-treating solution compositions pxovided by the invention:
Example A
Water 568 1 H2SO4 120 kg . . :~- .
Crystallized 250 kg (corresponds to 50.35 g Ferrous Sulfate Fe/Kg or 68.9 g Fe/l (Heptahydrate) solution) Sodium Chlorate 62 kg L0 The sulfuric acid~is added to water followed by the other ~
ingredients.~ The final solution has a density at 20C ~d20) ~ ;
- oi 1.370. The total weight of the solution i9 about 1000 kg, the solution containing 12.0% H2SO4, 25.0% ferrous sulfate, 6~2~/o sodium chlorate and the balance about 56.8% water.
5~ Example B
; Water 345 1 400 Kg solu. 400 kg (corresponds to containing 280 Kg 58.26 g Fe/Kg or Ferric Chloride 77.68 g Fe/l 0~ Hexahydrate ~ solution) i ; ;
Ammonium ~itrate 85 kg H2S04 170 kg The sul~uric acid is added last to the solution, the solu~ ~;
'~ tion having a density (d20) of 1.333. The total weight . o the solution is about 1000 Kg and contains 28% ferric ~ -chloride hexahydrate, 8.5% ammonium nitrate, 17% sulfuric acid and the balançe essentially 46.5% water.

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_ mple C ,~s, Water 570 1 ., H2S04 40 kg '~;' Crystalliæed 300 kg (60.A2 g Fe/kg or .
. Ferrous Sulfate 77.4 g Fe/l , (heptahydrate~ solution) ~, ;.. .
' Sodium Chlorate 90 kg '- , , .
The-sulfuric acid is added ~io the water followed succes- ' ?.
sively by ferrous sulfate and sodium chlorate to produce ~, a ~olution having a d~nsity (d20) of 1.282. ~The weight i ~ of the solution is about 1000 Xg and contains 4% H2SO4, ' .
i;,; -30~/O ferrous sulfate, 9~/O sodium chlorate and the balance '.~,, ~ about 57% water. ; `, ¦~ ' ' Example D
1~ 15 Water 498 1 .', 3' ~ . . ' ,;~:.
3; , H2So4 ~ 40 Xg Crystallized 357 kg '.. , ~ ':
Ferrous~Sulfate . ',:;',' ~ . (hepta,hydrate) 3~ 2~ Ammonium~c'hlorate 105 kg . '~
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~ . The sulfuric acid is added to the water followed succes~
j sivel~ by ferr~5 sulfate and ammonium chlorate to produce ,~ ' a solution having a density (d20) of 1.351. The weight of ,,;'.,',' ; , the solutiQn is ,about 1000 kg and contains ~% sulfuric ~',;~'; ' ';
~ 25 aci*, 35.7% crystallized ferrous sulfate, 10.5% ammonium ,, '`' ':
'I chlorate and the balance about 49.~/O water. ' .
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~ 1~6Z~4~7' Exam Water 335 1 ~
H2 S4 170 kg .;
400 kg solution .
containing 280 kg .. :of ferric chloride .hexahydrate400 Xg ;~ .
;
~ Sodium nitrate95 kg .;
- ! , 10: The suluric:acid is added last to the solution which .~:
has a density (d20) of 1.335. The total weight of solu-~- tion is about 1000 kg and contains 28% ferric chloride ~.
hexahydrate, 9.5% sodium nitrate, 17.0% H2S04 and the ~ ~ ;
balance about 45.5% water~ ` :
It is understood that re~erence to crystallized ,,?~ ' ~ ferrous sulfate means the heptahydrate, while referencè ;~.
:~ . to ferric chloride means the hexahydrate.
As illustrative of the use of solutions of the ~ foregoing~type in removing odors from organic wastes, the ;.
.~20~ ~ ~ following examples are given: . .
. ~ Example 1 ~,.
1, . . . .
In the txeatment of pig wastes, 3 kg of an odor~
l~ remo~ing solution are added per cubic meter o~ waste, said I ~ ~ solution having dissolved therein 25% by weight of crystal- :.~ -~ lized ferrous su~fate, 15% sodium chlor~ate, 6% sulfuric .
acid and the balance essentially 54% water. To assure a 3~ ~;
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1~;24g~'7 satisfactory pH in the final mix, a urther addition of 3 kg o~ sulfuric acid is made to the pig wastes The odor from the pig wastes was immediately abated and, after one day, was substantially eliminated~
The soluble reaction products comprised 246 mg of sodium chloride and 4.5 kg of ammonium sulfate per cubic meter.
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Example 2 Pig wastes are treated with 3.5 kg of an odor-10 removing solution per cubic meter of waste, the solution containing by weight 30~/O crystallized ferrous sulfate, 12.3% sodium chlorate, 5.5% sulfuric acid, and the balance . . ~, .....
essentially 52.2% water. The pH of the wastes is urther ,. j .
adjusted by the addition o~ 2.8 kg of sulfuric acid. The results obtained are the same as for Example 1.
~he soluble reaction products included about x 239 mg/l o~ sodium chloride and about 3.9 kg of ammonium - '. :'.. ::
sulfate per cubic meter.
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Example 3 To 1000 kg of human wastes is added 2 kg of an ,~!
odor-removin~ solution according to Example B containing 28% ferric chloride hexahydrate, 8.5% ammonium nitrate, 17% sulfuric acid and the balance essential`ly 46.5% water.
The odor was immediately abated and was long lasting. A ;
faint odor of garden compost remained.
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Th~ soluble products ormed included about 138 mg N02/Kg (850-9S0 ml), about 458 mg/kg ammonium sulfate, and about 856 mg/kg of ammonium chloride.
ExamPle 4 In the treatment of human wastes in a non-l~ ~ flushed caravan toilet, about 10 grams of solution is i ~ .
, proportioned per individual per day, the solution con-taining by weight 14% ferric chloride, 4 3% ammonium nitrate, 8.5% sulfuric acid andi the balance essentialIy ~' 73.2% water.
The soluble reaction products comprised about 244 mg N02/Kg, about 800 mg ammonium sulfate/Kg j~ ~ and about 1.5 gram ammonium chloride/Kg.
Example 5 ' lS Excess sludge from a pre-precipitation sewage ;
treatment is treated by adding 0.75~kg of solution per cubic meter thereof according to the compcsition of Example A containing about Z6.7/ of crystallized ferrous ~.
~ sulfate, abouit 6.6% sodium chlorate, about 12.7% H2S04 ..
. .
~i 20 and the balance essentially 54/0 water. The repulsive odor wàs immediately abated to a faint odor of mould. This `~
odor lasted to at least the dewatering and concentration .. ~
steps. The Iatter steps were facilitated due to a marked ~ 12-3'~

1~62~7 decrease ln sedimentation time and increase in the final solids content. The foregoing operation was carried out continuously for 6 weeks at a flow rate of 35 to 45 liters of excess sludge per second. ~;
S The soluble reaction products included about 25 mg/l of sodium chloride and about 120 mg/l of ammonium sulfate (87 mg/l 504). ~ ;
Example 6 ~
About 0.5 Kg of an odor-removing solution corres- L
ponding to Example C is added per cubic meter of excess ~-;
sludge from a pre-precipitation sewage treatment system, ;`
t~e iolution containing 30~fO dissolved crystallized ferrous ;
sulfate, 9% sodium chloriate, 4% sulfuric acid and essen-~ tially 57% water. The results obtained are similar to ~ i Example 5. In addition to the solution, the pH was adjus- ;```
ted to below S by adding 80 grams of sulfuric acid per ~5 . ::
cubic~meter of waste~.
The soluble reaction products include about

2~5 mg/1 of sodium chloride and about 126 mg/l o ammonium sulfate (92 mg/l S04).
~ Example 7 Excess sludge from a post-precipitation sewage treatment system is treated by~adding 0.5 Kg of odor-I, removing solution per cubic meter of waste, the solution - -13 ;"~
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comprising 35% of dissolved crystallized ferrous sul~ate, 7~6% sodium chlorate, 4% sulfuric acid and the balance essentially 53.4% water. Following the addition of the solution, the pH was further aajusted by the addition of 90 grams of sulfuric acid per cubic meter of waste~ The results obtained corresponded to those obtained in `
Examples 5 and 6. ;
The soluble reaction products included about 21 mg/l of sodium chloride, and about 138 mg/l of ammonium sulfate (101 mg/l SO4).
Example 8 Sewage previously treated mechanically to remove coarse solids is subjected to the method of the invention by adding 0.4 Kg of odor-removing solution per cubic meter of said sewage. The solution contained by weight 30% dis-.
solved crystallized ferrous sulfate, 9% sodium chlorate, ( . .. .
I~ 4% sulfuric acid and essentially 57% water. Following addi~
,;~, . .~ tion of the solution, the pH of the mixture was adjusted by i a further addition of 195 grams per cubic meter of sulfuric acid. The odor was immediately eliminated and spontaneous flocculation and sedimentation occurred. About 90~/O of the original phosphorus was removed.
The soluble reaction products included about 19.6 mg/l of sodium chloride and about 267 mg/l of ammonium sulfate (194 mg/l SO4).
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As will be evident from the foregoing examples, the composition of the odor-removing solution may vary ,,, . :.:
over a relatively broad range. Thus, the solution may .:. :- :
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comprise by weight about 3% to 25% sulfuric acid, about : . '

3~/O to 20~/o of an oxidizing agent from the group consisting ;.

of sodium chlorate and ammonium nitrate, about 10% to 40% ..
.-~
of an iron salt from the group including hydrates of fer- . :
rous sulfate and ferric chloride, and the balance at least , ~.
about 40% water. ~!, ~'' ': .
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~lthough the present invention has been des- ;
cribed in conjunction with pre~erred embodiments, it is to be understood that modifications and variations may be ;:
resorted to without departing from the spirit and scope /: : .
of the invention as those skilled in the art will readily understand~ Such modifications and variations are consi-dered to be wlthin the purview and scope of the invention ~: and the appended claims. ,~ .

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Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of reducing air-polluting odors emanating from a solids-containing organic waste product selected from the group consist-ing of organic waste products produced by metabolic processes including animal and human wastes, organic industrial wastes and sewage sludges which comprises contacting said organic waste product with an effective odor-abating amount of an aqueous acid solution containing an oxidizing agent selected from the group consisting of water-soluble persulfates, nitrates, chlorates and permanganates of ammonium ion and alkali metals in an amount sufficient to provide between about a and 68 mg 02/g of solution, a precipitating agent selected from the group consisting of water-soluble ferrous and ferric compounds in an amount sufficient to provide between about 28 and 70 mg Fe/g of solution, and about 3 to 25%
by weight of sulfuric acid; and maintaining said contact until said odor has been substantially removed.

2. The method of claim l, wherein said aqueous acid solution contains by weight about 3% to 20% of an oxidizing agent from the group sodium chlorate and ammonium nitrate, about 10% to 40% of an iron salt from the group including hydrates of ferrous sulfate and ferric chloride, and the balance at least about 40% water.

3. The method of claim 2, wherein the precipitating agent is ferrous sulfate heptahydrate.

4. The method of claim 2, wherein the precipitating agent is ferric chloride hexahydrate.

5. The method of claim 1, wherein the pH of the solution in contact with the organic waste is adjusted to below 5.

6. The method of claim 1, wherein the acidity is due to the addition of water-soluble acid-forming salts.

7. An odor-removing solution for use in reducing air-polluting odors emanating from organic waste products produced by metabolic processes and from organic industrial wastes including effluents, said solution comprising essentially: an aqueous acid solution containing an oxidizing agent selected from the group consisting of water-soluble per-sulfates, nitrates, chlorates and permanganates of ammonium ion and alkali metals in an amount sufficient to provide between about 8 and 68 mg 02/g of solution; a precipitating agent selected from the group consisting of water-soluble ferrous and ferric compounds in an amount sufficient to provide between about 28 and 70 mg Fe/g of solution;
and about 3% to 25% by weight of sulfuric acid.

8. The solution of claim 7, wherein said aqueous acid solution contains by weight about 3% to 20% of an oxidizing agent from the group sodium chlorate and ammonium nitrate and about 10% to 40% of an iron salt from the group including hydrates of ferrous sulfate and ferric chloride, and the balance at least about 40% water.

9. The solution of claim 8, wherein the precipitating agent is ferrous sulfate heptahydrate.

10. The solution of claim 8, wherein the precipitating agent is ferric chloride hexahydrate.

11. The solution of claim 7, wherein the acidity of the solution is due to the addition of water-soluble acid-forming salts.