CA1057866A - Microbiological method for removing pathogenic microbes and dissolved organic materials from liquids - Google Patents

Abstract

A B S T R A C T

The specification describes a method for removing pathogenic germs and dissolved organic substances from liquids.
Kefir milk acid bacteria in the form of a centrifugate, obtained from washing-out Kefir mould cultures are added to the liquid after suitable electrochemical precleaning. The liquid mixed with the bacteria is passed over a cylindrical column, whose filling bodies consist of cylindrically shaped fabric of antimagnetic stainless steel with a large surface.
On this the microorganisms of the Kefir group are deposited and form a biological lawn. When atmospheric oxygen is supplied and the liquid is repeatedly circulated through the column, the organic liquid contaminating materials take up the pathogenic germs as nutrient material so that as a result of the microbiological processes of the Kefir bacteria the liquids are freed from these materials.

Description

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In the removal of organic materials from liquids use iq made most frequently of biochemical methods whose efficacy depends upon the presence of organisms, present in the water in nature, such as Rotifera, Vorticella sp., Parameceae, Flagellum sp., Forticalle camparum, Protozoon sp. and the presence of oxygen.
Generally contaminating material~ from the macro to the .
micro range, that is to say from 200 to 10 micronæ are re~
moved by sedimentation from the liquid before it is brought into contact with an equiva-ent quantity o~ the above~
mentioned microorganisms and minute forms of life either in .-a droppin~ method or in an activated sludge method with the simultaneous supply of atmospheric oxygan.
Colloidal contaminating materials, colloidal su~pensions ; 15 and materials in the sAme order of size as ions are firstly enzymatically converted in such biochemical stages and then partly oxidized by metabolism of the organisms and are partly : adsorbed by becoming attached to the organiqms.
A ~ecessary condition for obtaining a high efficiency is the presence of co~ditions which are favourable for the organisms, that is to say the right temperature, a pH-value ~ near neutral, the absence of poisons, such as bactericides, : in3ecticides, heavy metals starting at a certain concentration and the presence of phosphates and nitrogen compounds.

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Activated aludge installation~ with optimum degrees o~
efficiency are generally operated with e proportion of activated sludge of 4 gram per liter.
~ he time the material remains in the raaction ~p~ces de-5 pends upon the composition of the contaminating materials in ; ~ -the liquid and amounts to between 1 hour to, in some cases, 48 hours in the case of particularly resistant sewagel , In the case of purely domestic sewage the dissolved organic substances consist of carbohydrates, proteins and sugars. ~hey make a rapid chemical degradation possibleO How-ever, in the case o~ such cleaning processes after half an hour~on average 250 ml of sludge ~g~ can be deposited, as measured in an Imhoff funnel, per liter of sewage sludge mixture and such sludge can only be dewatered with difficulty ; ;
even if owing to dangers to hygiene the sludge is placed in so~called decomposing towers before dewatering.
Xighly concentrated sewage, as for example from slaughter~
houses, dairies, jam factories and premises for disposi~g of animal bodies, can in accordance with experience to date only be sufficlently purified in so~called prolonged activation installations, in the case of which the charging rate per I unit volume must partly be reduced to 0.3 kg BSB5 per square meter of activated space per day.
~ In the case of sewage from paper and pulp industries ~;
3 25 similar difficulties occur9 in this respect more especially glucosides, lignins, tannins and xylose resulting from the break-down of wood make biochemical degradation more difficult.
Very often in the case of such sewage BSB5 discharge values are obtained after the biochemical cleaning which are ver~
satisfactory but however the values for potassium permanganate consumption and chemical oxygen requirement in accordance with the dichromate method are often unacceptably higher than , ~ 3 ;.

is the case with the measured biochemical oxygen require-ment measured. The differences 8how in many cases that with ~he biochemical processes only partial degradation occurs and in the case of the BSB5 measurement the actual residual load is not covered.
l~he cause for the differences in the last-mentioned example are to be found substantially in the insufficient enzymatic break-down of the contaminating materials in the liquid before the actual biochemical oxidativn ~d adsorption.
Agricultrual sewage involves difficulties similar to those occuring with known biochemical degradation processes.
In the case of sewage from mass pig farming it i5 known that approximately 30% of the protein materials fed leave the animals without digestion and it is only after complicated splitting processes that they are in a condition fit for oxidation by organisms in biological installations.
In normal domestic sewage numerou~ pathogenic microbes are present which cannot be biochemically degraded and if at all can only be removed by adsorption on biological sludge from the sewage. It is possible to assume with certainty that in every sample of normal domestic sewage at least 1,000,000 microbe~ are comprised per ml; in this respect it is for the most part a question of Escherichia coli, though however the proportion of facultatively pathogenic microbes is very high so that sewage is to be considered highly infectious.
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Efficient biochemical cleaning installations remove 98~ of the microbes by adsorption. On the basis of the abovementioned example as a result in the discharge from a 30 well operated biological cleaning installation still 10,000 microbes in all remain per ml~ In the case of public waters whi~h are permitted for human bathing and for drinking by animals, not n~re than 10 microbes per ml should be present.

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:............ ,, . ,; :: .. ,-. , ,. -Owing to the increasing quantities even of puri`fied qewage in comparison with the quantit~ of water on the sur-face of the ~arth which always re~ains the same, the danger of infection by sewage is therefore increasing steadily.
~he method in accordance with the invention avoids the above-mentioned disadvantages b~ the use as a preliminar~
stage of an electrochemical proces~9 the electro-M-method, by means of which all colloidal materials and substantially ;
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all colloidal suspensions are removed from liquids. ~he electro-M-method is assumed to be known.
The liquids comprise after the process substa~tially only parts of colloidal suspensions and the dissolved organic substances in addition to inorganic contaminating substances.
Since the electrochemlcal process brings about a sub-stantial removal of all microbes from the liquids, the dis-charged liquid is inocculated with lactic acid bacteria of the Caucasian Kefir group.
In this respect it is a question of microbic organisms, whick even in acidic condltion and up to pH-values of 10 re-produce themselves by cell division very rapidly in the pre-sence of atmospheric oxygen and after suitable conditioning ~ -to conditions oxidize, more especiall~ sugar, glucose, pro-teins and fats~ -It has been found in tests that owing to the capabilit~
~` 25 of Kefir organisms to degrade proteins a certain cannibalism -`~
results which has a favourable ef~ect on the pathogenic microbes also existing as is known on a protein basis in the liquids.
~he consequence of the procedure in which firstl~ by means of electrochemical processes or chemical processes, which are al50 possible but owing to the large amounts of sludge involved and of other consequences which are disadvan-' :~
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tageous for protectin~ water, such as salting out, increasing the sulfate load etc., the sewage or other liquids is sub-stantially freed of all contaminating material~ with the exception of colloidal suspensions and dissolved materials and is then exposed to the action of Kefir microorganisms, i~
that as compared with prior art biochemical processes a de-cidedly lower quantity of sludge is obtained as excess sludge.
It has been found in several cases that it is only after the additional floculation with organic precipitating ma-terials that small quantities of sludge can be removed fromthe purified water.
The Kefir microorganisms used in the method of the in-vention are cultured from Kefir mould with the addition of substantially defatted milk at room temperature, the milk serving as a nutrient material for the organisms. As a result the nutrient solution is decomposed and a spherical coherent culture remains. ~he culture is sieved out and washed with drinking water.
After the first washing operation preferably a part of 20 the culture remaining is added to ten times as much water~ -then dispersed and the suspension is then centrifuged. ~he centrifugate is used as a material for inocculating the liquid to ba cleaned, to which it i9 added.
It i9 also possible to add the culture after the first 25 washing operation directly to the liquid to be cleaned It has been found in accordance with experience that in the case of the use of the centrifugate as inocculating material the inocculated water should be ~upplied to a drip body-like column in which however departing ~-rom d~}p bo~d~
fillin~ material filling bodies with a cylindrical form are used con~istin~ of stainles~ antimagnetic steel fabric with ~ mesh width of less than 300 microns. This leads to a ~ubstan-; 6 , .

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tial increase in the surface in the column as compared with normal drip body material and per gram of the filling body material for the lawn of microorganisms a 3urface of 2 square meters is made available.
p ' 5 ~he liquid inocculated with the microorganisms i~ ~x~
several times through the column. As is the case wit~ a drip body the entering water is pas~ed by a rotary sprinkle onto the column.
Examples for the reduction of the chemical oxygen :require-ment in accordance with the dichromate method~
(1) Precleaned sewa~e from a toilet paper factor~
after electrochemical treatment with the electro-M-method CSB 40 mg/l, 1.1 after addition of 2 ml of microor~anism oentrifugate per liter and 2 hour~ of treatment time in the drip ' column CSB 10 mg/l.

(2) Precleaned domestic sewa~e ;
after electrochemical treatment with the electro-M-method CSB 184 mg/l, 2.1 after addition of 5 ml of microorganism centrifugate per liter and 4 hours of treatment time in the drip column CSB 28 mg/l. , ' (3) Precleaned textile sewa~e~water_from disper~ion d~in~

3 vats after electrochemical treatment with the electro-M-method CSB 296 mg/l, 3.1 after addition of 10 ml of microorgani~m centrifu-., .
~, gate per liter and 2 hour~ of treatment time in the drip column CSB 194 mg/l, 3.2 after a further 2 hours :i CSB 82 mg/l, 3.3 after a further 2 hour3 CSB 41 mg/l.
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: (4) ~he water in accordance with 3.2 within 2 hours 50 % of precleaned communal water was added, entry C~B 225 mg/1,

4.1 after 2 hours of treatment time in the drip column CSB 62 mg/l, . 4.2 after a further 2 hours ; CSB 34 mg/l.

(5) ~he water in accordance with 4.2 within 1 hour 50 %
precleaned textile sewage was added.
~0 entry CSB 3~0 m~/l, 5.1 after 2 hours of treatment time in the drip column CSB 194 mg/l, after 4 hours CSB 152 mg/l, after 8 hours CSB 48 mg/l. ~ :
~he BSB5 of this sample was 20 mg/l.

(6) Precleaned sewage from_a skin ~lue factor~
. after electrochemical treatment with the electro-M-method . 20 CSB 883 mg/l,`
6.1 after addition of 20 ml of microorganism cen-trifu-: gate per liter and 2 hours of treatment time in the ; prepared dripping column CSB 182 mg/l, after 6 hours of treatment time in the drip column ` C~B 52 mg/l.
:~ ~urther~ore, the inocculation of classical biochemical :
~, activated sludge installations with the centrifugate of the :
:l Kefir microorganisms or the washed-out mould cultures show .: substantial improvements in the efficiency on the basis of the treatment time of the water in the biological stage.
~ However no substantial change in the excess sludge quan .~:i tities could be detected, something which could be clearly 8 ::
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found in the case of addition of the inocculating composition in a pure form.
Visible residual turbidity was decreased b~ the addition of Kefir microorganisms to the water and the odour in contrast 5 to the discharge from known biological stages is no longer ~ `
m~uldy or earth-like and instead i6 fresh or neutral. ~ -~he microorganisms can be considered to be extraordinarily stable, as a few test examples will show Example 1: The culture taken from the milk nutrient solution was stored in a Petri dish for 8 days in a ~terile cupboard and then washed out and centrifuged. In the centrifugate numarous Kefir microorganisms were comprised which after the addition of nutrient so-lutions reproduced very rapidly.
Example 2: ~he centrifugate obtained in example 1 was stored for 26 days in a bottle with a ground glass stopper with 50 % ullage at a temperature of +6C in a re-frigerator and then the centrifugate was used again for inocculating sewage. In the centrifugate the ~-microorganisms were present in great numbers. Dead cells could not be detected.
~xample 3: A drip column inocculated with the centrifugate in ; accordance with example 2 had after 8 weeks of test procedure such an extensive culture that further inocculation was no longer necessary even in the ~;
case of cleaning tests with the most various diffe-rent forms of sewage.
~ii The aerobic microorganisms passing with the sewage into the column, which are used in the case of normal biochemical cleaning, were not impaired by the Kefir microorganisms.
However, it could be found in this case as well that the :' -.`' .

3L~5'~3 excess sludge quantity was substantially reduced so tha t it can be suppo~ed that the main cleanin~; effect can be attributed to the Kefir microorganisms.
In the case of the use of the drip columrL it was pre 5 ferred to work with a body whose height i~3 20 time~ its dia- :
meter, The overall volume was reduced by 50 % by the metal filling bodibs.

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Claims (8)

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

1. A method for removing pathogenic germs and dis-solved organic substances from liquids characterised in that Kefir milk acid bacteria in the form of a centrifugate, obtained from washing-out Kefir mould cultures, are added to the liquid after suitable electro-chemical precleaning and the liquid mixed with the bacteria is passed over a cylindrical column, whose filling bodies consist of cylindrically shaped fabric of anti-magnetic stainless steel with a large surface, on which the micro-organisms of the Kefir group become deposited, form a biological lawn and in the case of the supply of atmospheric oxygen and multiple passage of the liquid through the column the organic liquid contaminating materials finally take up the pathogenic germs as nutrient material so that owing to the microbiological processes of the Kefir bacteria the liquids are freed from these materials; characterised in that the liquids to be cleaned for the purpose of precleaning by means of chemical precipitation are freed from substances present in the macro to colloidal ranges of size.

2. A method in accordance with Claim 1 in which said precleaning is carried out by sedimentation or a combination of sedimentation and normal biochemical aerobic treatment before the addition of the Kefir milk acid bacteria.

3. A method in accordance with Claim 1 in which the biological lawn formed by the addition of said Kefir bacteria is enriched with conventional aerobic microorganisms and in which said Kefir bacteria are continuously added to said liquid and thus become numerically superior with respect to other bacteria in said liquid.

4. A method in accordance with Claim 1 in which said Kefir milk acid bacteria are cultured with skimmed milk powder mixed with drinking water as a nutrient solution.

5. A method in accordance with Claim 1 in which after the treatment of said liquid with Kefir milk acid bacteria, said liquid is subjected to an electrochemical coagulation to remove any remaining bacteria and colloidal suspension.

6. In a method, as claimed in Claim 1, said Kefir bacteria being of the type obtained by washing a Kefir mold culture by dispersing said culture in a large amount of water; and subsequently centrifuging the dispersion to obtain said Kefir bacteria as a centrifugate.

7. In a method, as claimed in Claim 1, wherein said aqueous liquid is subjected to a pretreatment before introduc-tion of said Kefir bacteria, which pretreatment reduces certain impurities in said aqueous liquid.

8. In a method, as claimed in Claim 7, said pre-treatment comprising the steps of flocculating said certain impurities in said liquid by passing an electric current through said liquid; and subse-quently separating the flocculate so formed, from the liquid.