DE19644714A1 - Biological treatment of fat - Google Patents

Abstract

Process for decomposing fat- and/or oil-containing emulsions and solutions, particularly cooling lubricants used during the machining and processing of metals, comprising the stages of (a) inhibiting or deactivating preservatives, bactericides or biocides present in the emulsion; (b) adjusting and maintaining the pH of the emulsion in the range 4.5 - 10.5 (6.6-7.8) by addition of acids and/or bases and/or buffer solutions; (c) adjusting and maintaining the temperature of the emulsion at 15-75 (20-40) deg C; (d) adjusting and maintaining the oxygen content in the emulsion at above the minimum threshold level for aerobic metabolism, preferably at above 2 mg/l, by leading in air and/or oxygen; (e) incorporating a bacterial mixture capable of metabolising, decomposing and breaking down the organic components of the emulsion or solution, principally hydrocarbons, emulsifiers, surfactants, antioxidants and soaps, especially a bacterial mixture dominated by Bacillus subtilis types and particularly the preparation available as "DBC-Plus Type R5 or Type L" (RTM Environmental Protection Agency, U.S.A.); (f) decomposing the organic molecules in the emulsion by fermentation until the concentration of organic material is below the minimum allowable threshold value, e.g. 100 ppm hydrocarbons; and (g) separating the water from the biomass and solid material in the fermentation product e.g. by filtration or centrifuging.

Description

The invention relates to a method for breaking down fat and / or oil emulsions and solutions, especially in metalworking cooling lubricants used.

Cooling lubricants are used to derive the shape during machining process particularly in the case of separating or Forming heat and the reduction of friction between the cutting edges the and the workpiece or the chips. They essentially consist of Water, mostly 30-50% oil (mineral oil and / or natural oil) and emulsifiers such as B. surfactants. Other organic components of the cooling lubricants can partial phosphoric acid esters, antioxidants, soaps and / or high temperature resistant glycols. The exact compositions of the cooling lubricants vary depending on the application and manufacturer.

Cooling lubricants are used over long periods, usually several Months, circulated in the machines of a manufacturing plant. To the Decomposition of the cooling lubricants by microorganisms during this time Avoid using different preservatives, or bactericides Biocide added. Several studies are devoted to avoidance the biological decomposition of cooling lubricants. In the German Patent DE 40 00 126 C2 is a method for reducing the decomposition described by air supply.

After a certain period of time, cooling lubricants become unusable, especially because of the ongoing thermal and mechanical Stresses the hydrocarbon molecules of the cooling lubricants be destroyed. They are then usually considered together with waste oil "Secondary fuels" burned as hazardous waste. This disposal  Driving are very expensive and complex because of the emission of toxic exhaust gas components must be avoided.

The object of the invention is to provide a degradation process for cooling lubricants create which is as environmentally friendly as possible at low cost Disposal of the cooling lubricants enables.

This object is achieved by the method according to Patentan spell 1 solved.

A bacteria is an essential process step in the emulsion Mixture introduced, which the organic molecules through metabolism the emulsion or solution, essentially the hydrocarbons that Emulsifiers such as B. surfactants, the antioxidants and the soaps decomposed and breaks down. For other organic components (glycols, phosphoric acid reteilester) of the emulsion, the bacterial mixture must also break it down be suitable.

Certain mixtures of bacteria defined in their structure that are manufactured industrially, in particular as lyophilized products known from different applications to oils, fats, paraffinic, naphthenic and aromatic hydrocarbons as well as other organic ones Clear connections. Suitable bacterial mixtures for quick Degradation of the organic components of the cooling lubricants are an example example under the designation DBC-Plus Type R5 or Type L at the ENVIRIONMENTAL PROTECTION AGENCY of the U.S.A. she consist mainly of Bacillus subtilis species.

Before the introduction of the bacterial mixture, there are edges in the emulsion create conditions for efficient biodegradation. First are those in the emulsion during manufacture or during operation to deactivate the preservatives or bactericides. Then  must adjust the pH, temperature and oxygen content of the emulsion to values be adjusted and maintained, which the aerobic metabolism of the Enable and promote bacterial mixing as far as possible.

The optimal range for pH is between 6.6 and 7.8. While The degradation of the hydrocarbons in the emulsion must be continuous Acids are added because by breaking down the soap molecules through the microorganisms oils, fats and alkali / potassium hydroxide (potassium hydroxide solution) arise and the emission without regulatory intervention with time for the microorganisms become too alkaline. In any case, the pH value be kept between 4.5 and 10.5.

The optimal temperature range is between 30 and 37 ° C. To the Necessity to heat the emulsion during the mostly over 50 To avoid days of decomposition can be a temperature of around 20 ° C can be selected. At this temperature, when using the bacterial mixture called a breakdown of the organic molecules of about 50,000 ppm to below 100 ppm possible in about 70 days. The temperature the emulsion should not drop below 15 ° C during fermentation and do not exceed 75 ° C.

The oxygen content is to be kept at more than 2 mg O ₂ / l by air / oxygen supply in order to maintain the aerobic metabolism of the submerged microorganisms introduced into the emulsion.

After fermentation of the emulsion until it falls below the permissible Limit value for organic molecules in water (in the federal states Hesse and North Rhine-Westphalia, for example 100 ppm) can ver permanent water can be discharged into the sewage system without any problems other purposes, for example for cleaning or as cooling water in the Manufacturing plant can be used. The biomass is non-toxic and can to be deposited safely. It is also possible to use the remaining biomass  to use as fertilizer or for wastewater treatment in sewage plants to use.

Cooling lubricants often have too high a hydrocarbon concentration or are used as pure cutting oils without water components. In In these cases, water and possibly emulsifiers must be used before fermentation be added. The addition of emulsifiers can then also be necessary when large hydrocarbon molecules by temperature influences during use of the cooling lubricant in smaller, water insoluble hydrocarbon molecules are broken. Alternatively, you can these oils can be finely distributed in the emulsion by blowing in air.

Further features of the invention emerge from the subclaims and from the following description of preferred embodiments of the inventive method.

The application of the procedure described begins when there is a change the emulsions or cooling lubricants used in a company medium is necessary for technical reasons because the emulsions, Dispersions and / or solutions are no longer usable - e.g. B. due to impurities, active substance emaciation, decomposition product ten etc.

The technical-microbiological process is based on 3 stages:

• 1. Pretreatment of coolant emulsions and not water miscible cooling lubricants;
• 2. aerobic fermentation of the prepared emulsions;
• 3. Separation level of water, biomass, insoluble residues (Graphite, metal abrasion, splinters and sanding sand etc.).

Pretreatment of the emulsions

For biodegradation, all become non-cutting and cutting Processing of metals used lubricants and cooling lubricants prepared. Unless mixed with water for microbiological treatment bare cooling lubricants must be present in the pretreatment stage Oil products initially in emulsions by adding solvents as Solubilizer, of special surfactants or emulsifiers with simultaneous Intensive mixing with water (oil / water emulsions) can be transformed.

Microbiological degradation of oils and other hydrocarbons is only possible in the presence of sufficient water. The measured Concentrations of oils in the technically used emulsions on average 48,000 mg / l to 12,000 mg / l.

The emulsions thus obtained and / or the water-mixed emulsions cool lubricants are added by adding acids or bases pH to values between 4.5 and 10.5, preferably in pH ranges set between 6.6 and 7.5. For this purpose, preferably organic Acids such as gluconic acid, succinic acid, lactic acid and in particular Fruit acids: citric, malic or tartaric acid, acetic acid and their Ester or base / alkalis such as potassium hydroxide or ammonia, ammo niacal solution, as well as buffer substances phosphate buffer, carbonate and especially sesquicarbonates (sodium bicarbonate) are used. During the the entire degradation process, the pH is readjusted, insofar as this should be necessary.

The pH settings can be changed during treatment and later Fermentation in control sections can be carried out manually or by a device for automatic pH control and adjustment.  

Another important step is the inhibition or elimination of preservatives bactericides or biocides in the cooling lubricant emulsions. In the cooling lubricants according to the classification and definition according to DIN 51 385/1 in particular, substances and / or groups of substances are used as biocides, which are intended to prevent the growth and / or multiplication of microorganisms, alone and in a mixture and by admixing during the period of use of the products / preparations and the emulsions used:

• - formaldehyde and
• - S, N-heterocycle-1,2-benzothiazolone; Hexahydrotriazine, isothiazo londerivate - formaldehyde releaser, so-called formaldehyde de pot connections -,
• - Phenols and derivatives: e.g. B. o-phenylphenol,
• 5-chloro-2-methyl-, 2-methyl- or 2-octyl-4-isothiazolin-3-one,
• - Quaternary ammonium compounds.

Heavy metals in organic or ionic bonds - for Example the Zn and Na salt of 1-hydroxypyridine-2-thione derivative - as well Organotin compounds encountered.

The inhibition, destruction or conversion of the biocide can be done in the form like
Formaldehyde and formaldehyde derivatives / depot compounds:

2 CH ₂ O + H ₂ O ₂ → HIGH ₂ -OO-CH ₂ OH + 2 NaOH → 2 HCOONa + H ₂ + 2 H ₂ O

Hydrogen peroxide and subsequently sodium can be used for this reaction be used hydroxide and simplifying sodium percarbonate or other per connections.  

The consequence of this treatment is that only after the implementation of the form aldehyde the pH is adjusted. Implementation in the emulsions takes place in the temperature range between 15 and 75 ° C, the reaction time is temperature dependent. Preferably at temperatures between 20 and 37 ° C worked. The reaction of the formaldehyde conversion is completed within 12 hours, and the treated emulsion is already in a temperature range that is suitable for the following Fermentation is beneficial.

Phenols / phenolates and their derivatives are subject to biodegradation the 2nd stage. Identification in emulsions can e.g. B. with the help of Iron III chloride happen, after which a red-violet color develops.

To avoid possible disturbances at higher concentrations above the MIC value (MIC = minimum inhibitory concentration) Phenol and its derivatives by adding 0.5 to 3% poly ethoxysorbitan oleate / polyoxyethylene sorbitan monooleate (e.g. from the company ICI sold under the brand name TWEEN-80) can be inhibited.

This inhibition and / or inactivation with additions of polyethoxysor bitanoleate and lecithin - u. a. also soy lecithin - can be used for many conserves agents / biocides are used; this also applies to quaternary ammonium compounds and organotin compounds and amphoteric surfactants.

The chemicals used in the emulsions are based on the known reaction courses in terms of quantity to the existing ones Biocid amounts matched.

fermentation

After completing the preparation for biodegradation upcoming coolant emulsions becomes the 2nd stage, the "aerobic  Fermentation ", initiated. The fermentation can be introduced into the container in which chemical pretreatment is also carried out has been. Alternatively, the approach can be in a separately provided Fer pumped around.

The approach envisaged for microbiological degradation will be based on a few basic parameters checked.

The use of carbonates and sesquicarbonates or fruit Acids as pH regulating and / or buffering substances prove to be very good expedient. It has been shown that during the running fermenta It is possible to add these substances via an automatic pH control Zen.

The temperature to be maintained during fermentation is normal usually in the range between 20 and 40 ° C. Preferably, the Set the temperature between 30 and 37 ° C. Again, for one automated temperature control.

As the fermentation is mainly carried out under aerobic conditions, it is necessary to use artificial aeration when using fermentation tanks and tanks. The volume of air blown in is between 0.1 and 0.5 m ³ air per minute and an average of 0.25 m ³ air per minute for a tank volume of approximately 1 m ³ . Of course, small amounts of air are also possible.

The fermentation batch must be kept in motion in the fermentation tank / bioreactor. An agitator can be used for this, turbulent air injection can be carried out or mass can be circulated by pumping. Several of these measures can be combined. It must be ensured that the amount of air present in the treated emulsion is evenly distributed, so that the oxygen concentration is preferably not less than 2 mg O ₂ / l.

Biomass or the lyophilized powder of the bacterial mixture tested for the microbiological degradation of cooling lubricant emulsions are used as inoculum. A cell number in the fermentation batches is presented, which is between 10 ³ CFU per ml (CFU = germ-forming unit) to 10 ¹⁰ CFU per ml of emulsion to be prepared. Preferably, an inoculum is used which, in the fermentation batch, presents a cell count of 10 ⁶ bacteria per ml of emulsion to be fermented. In contrast to the test instructions described for determining degradation rates - in particular for examining total degradation - for example DIN 51 828, OECD Confirmatory Test, Simulation test or Coupled Units Test, which use microorganisms from activated sludge plants as inoculum - are defined in the present method Culture mixtures, preferably saprophytic bacteria, are used, taking into account the compositions of the emulsions to be treated, which are found according to given chemical analyzes. One of these mixed cultures is deposited under the name DBC-Plus Type R5 at ENVIROMENTAL PROTECTION AGENCY (EPA) - USA. This mixture of cultures is originally intended for the biological degradation of oil accidents in the maritime sector and has proven itself in the described method according to the invention.

In contrast to those in standard procedures for determining the fast biodegradability of lubricants and related products sen - see for example DIN 518 28-2 / draft from March 1995 - as an inoculum used wastewater from biological stages of a municipal sewage treatment plant plant with more or less random bacterial composition, are defined bacterial mixtures in the method according to the invention used. These defined mixtures consist of optional anaero beers and aerobes and perform the bioconversion of  Hydrocarbons through both catabolic and metabolic enzy Matic implementations - this runs both under aerobic and anae robes conditions. Dominant and for the quick mining of the coals however, the aerobic conversion is decisive for hydrogen.

If necessary, the addition of nitrogen and phosphate significantly promotes biodegradation. At the start of the degradation process, about 20-50 ppm nitrogen and about 5-20 ppm phosphate (P ₂ O ₅ ) can be introduced, and it may be necessary - depending on the composition of the treated emulsions or solutions - at certain intervals NPK solutions containing approx. 5 ppm N, 1 ppm P ₂ O ₅ and a trace of potassium (K ₂ O). In numerous studies, an ideal relationship to the biodegradation rate has been found if a ratio of COD / COD: N: P ₂ O ₅ = 100: 15: 5 was present (COD / COD = chemical oxygen demand / chemical oxygen demand). Bacterial mixtures of the species used are listed in the National Contingency Plan of the ENVIRONMENTAL PROTECTION AGENCY (EPA) / USA

The bacterial mixtures - like all bacteria - develop best under certain external conditions, which at the same time influence the ability to biodegrade organic compounds. For this reason, each degradation process is checked at short intervals with measurements of the pH value, the prevailing temperature, the conductivity, the COD / COD value and the prevailing O ₂ quantity. Cell number determinations are also carried out. The measurement of the microbiological degradation of hydrocarbons was carried out with an IR photometer. The measuring principle is based on the NDIR absorption according to DIN 38 409 H18. (NDIR = non-dispersive infrared spectrophotometry).

Depending on the composition of the metalworking solutions and the cooling lubricant emulsions the time to be spent is less Compliance with the influencing parameters described above between 20  and 80 days until both the oil degradation was significantly below 100 ppm as well also the surfactant degradation (total degradation) has happened and thus the initiation in a local sewer network. It is also possible to post Implementation of the separation process - 3rd stage - the remaining water to be used for further purposes as process / process water.

The diagram shown in Fig. 1 shows the course of the hydrocarbon degradation in a cooling lubricant emulsion in the treatment according to the inventive method. Starting from a concentration of 20,000 ppm, the hydrocarbons are broken down by fermentation to less than 100 ppm within 64 days. The increase in the hydrocarbon concentration which can be observed after about 14, 22 and 34 days is due to the splitting up of molecular groups which release there through oils, fats, benzene rings, hydrocarbons etc. The diagram shown in Fig. 2 shows the percentage degradation rate of the hydrocarbons.

separation

The suspension prepared in the fermentation containers is in a last stage of separation of water, biomass and insoluble residues, made of graphite, metal abrasion, chips and / or sanding sands etc. may exist, if necessary. The out armament of such a separation stage depends on the intended goal. In most cases, simple filtration is all it takes to get solid components cut off. Further treatments to separate the biomass Centrifugation is possible. Filtration is often sufficient in the final stage with subsequent introduction of the liquid amount into an oil separator.

Documentation of the initial values and the course as well as the values of the biodegradation achieved must be in the operational and public Chen interest. The other hand are from these values  to derive lungs. In particular, one connected in the sewer network biological sewage plant the supply of the biomass with the fermented Solution for solving your own tasks. Do support the supplied cultures due to their adaptation to the mined Mixtures of substances the sometimes problematic work of the sewage treatment plants. The one The pipe can only be operated with the approval of the municipal wastewater associations happen (indirect discharge approval).

Claims (9)

1. Process for the degradation of greasy and / or oil-containing emulsions and solutions, in particular cooling lubricants used in metalworking, characterized by the following steps:

• a) inhibition or deactivation of the preservatives, bactericides or biocides present in the emulsion;
• b) adjusting and maintaining the pH of the emulsion in a range between 4.5 and 10.5, preferably between 6.6 and 7.8, by adding acids and / or bases and / or buffer solutions;
• c) adjusting and maintaining the temperature of the emulsion in a range between 15 and 75 ° C and preferably between 20 and 40 ° C;
• d) Setting and maintaining an oxygen content in the emulsion above the minimum limit for aerobic metabolism, preferably above 2 mg / l, by supplying air and / or oxygen;
• e) Introducing a bacterial mixture which metabolizes the organic molecules of the emulsion or solution, essentially the hydrocarbons, emulsifiers such as. B. tensides, antioxidants and soaps decomposes and degrades, in particular introducing a bacterial mixture dominated by Bacillus subtilis species, as deposited, for example, under the name DBC-Plus Type R5 or Type L with the ENVIRIONMENTAL PROTECTION AGENCY of the USA;
• f) degradation of the organic molecules in the emulsion by fermentation until the value falls below a permissible limit for organic molecules, e.g. B. 100 ppm hydrocarbons;
• g) separation of the water from the biomass and possibly the solids of the fermentation product, in particular by filtration and / or centrifugation.

2. The method according to claim 1, characterized in that the emulsion before fermentation to a hydrocarbon concentration of less is diluted as 50,000 ppm. 3. The method according to claim 1 or 2, characterized in that in the Emulsion present, not water-miscible hydrocarbons Addition of solvents and / or emulsifiers with simultaneous intensi ver mixing in the emulsion. 4. The method according to any one of the preceding claims, characterized shows that there are no water-miscible coals in the emulsion Hydrogen can be distributed in the emulsion by blowing in air. 5. The method according to any one of the preceding claims, characterized records that to adjust the pH organic acids, in particular lactic acid, succinic acid, gluconic acid and / or fruit acids, be used. 6. The method according to any one of the preceding claims, characterized records that in an emulsion component of formaldehyde or a Formaldehyde derivative as a biocide whose inhibition by adding Hydrogen peroxide and then sodium hydroxide. 7. The method according to any one of the preceding claims, characterized records that in an emulsion component of formaldehyde or a Formaldehyde derivative as a biocide whose inhibition by adding Sodium percarbonate or other percarbonates. 8. The method according to any one of the preceding claims, characterized records that in an emulsion component of phenols or phenol-De rivat as a biocide, its inhibition by adding polyethoxysorbita noleate or polyoxyethylene sorbitan monooleate takes place.   9. The method according to any one of the preceding claims, characterized records that the biodegradation of the hydrocarbons by addition is promoted by nitrogen and / or phosphate.