DE2130922A1 - Process for the biological treatment of liquids - Google Patents

Description

Process for the "biological treatment of liquids

The invention "relates to the treatment of organic waste materials and in particular the biological treatment of thermally conditioned sludge water.

The fluids obtained from thermally conditioning dewatered organic sludges, particularly sewage sludge, albeit in relatively small volumes present dissolved organic solids, which have a large biological Oxygen needs (BOD) possess and their cleaning and their destruction brings in the construction of waste treatment plants or from sewage treatment plants problems. In general, these liquids are used in the wastewater treatment plant recycled and they are used to dilute the raw sludge and then they are with. known procedures biologically treated.

It is known that Schlanmiwasser undergoes a separate bio-treatment is only accessible when diluted with water or raw waste water. It has now been found that by using

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of the process according to the invention, the liquids that one when sludge is thermally conditioned, it is obtained directly, essentially in undiluted form, from a separate biotreatment can be subjected, and that one still has a satisfactory decrease in the biological oxygen demand in the resulting drain. At the same time, a high treatment speed is achieved because the higher Assimilation and oxygen transfer rates, which are obtained from the separate biotreatment, take advantage of.

• The method of the invention is through the following stages marked:

(a) The liquids are placed in an aeration tank,

contains biological sludge that has been previously acclimatized.

(b) The mixture is kept in the tank with a gas containing oxygen for more than 2 hours and until a sufficient level dissolved oxygen is present, which is sufficient to support aerobic biological growth, stirred.

(c) The mixture is transferred to a settling tank to separate the accumulated biological sludge.

(d) Biological sludge that has settled is recycled in the aeration tank and

(e) biological sludge is removed from the aeration tank at a rate approximately equivalent to the rate of accumulation of biological sludge.

The invention will be described with reference to the accompanying drawing explained in more detail.

The liquids that are processed are obtained by heat treatment or by moist air oxidation of organic ones Sludges according to known methods (see, for example, "the U.S. Patents 2,277,718, 2,84-7,379, 3,155,611, 3,272,739, 3 272 7 ^ 0 and 3 359 200). The liquids are obtained by decanting, draining or dewatering the thermally conditional

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ned sludge by vacuum filtration, centrifugation, settling, Filter presses or other dewatering devices.

In the known sewage treatment plants or waste water treatment plants, loading rates in the range of 0.2 to 0.75 kg biological oxygen demand per day per kilogram of mixture of volatile liquid and suspended solids are used in the biotreatment systems. In the method of the present invention, sludge water is treated at a loading rate that is substantially higher than the usual loading rate without any loss in BOD removal efficiency. For example, BOD removals in excess of 90 % can be obtained at loading rates up to 5.0 kg of BOD per day per kilogram of mixture of volatile liquid and suspended particles. The loading rate when carrying out the method according to the invention is between approximately 1.0 and 5 »C kg BOD per day per kilogram of mixture of volatile liquid and solids (mixed liquor volatile solids).

The liquids are continuously in the aeration tank introduced and continuously passed therefrom into the settling tank with such a flow rate that the residence time in the ventilation tank is at least 2 hours. The oxygen-containing gas, preferably ordinary air, is in a Added speed sufficient to keep the dissolved oxygen content so that the aerobic biological Growth is supported accordingly. This can conveniently be achieved by using a mechanical turbine aerator used.

The temperature is kept in the range between 25 and 40 ^° C. in the aeration tank. The temperature can be obtained by an electric heater or by other means, such as steam coils, are regulated, which are listed in the accompanying drawings as an example, or can be used by the thermally conditioned sludge heat by the liquid

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that are to be bio-treated in indirect heat exchange with the thermally conditioned sludge.

In those cases where the phosphorus content of the supernatant liquids to be bio-treated is insufficient to result in biological growth (for example, when the presence of metal ions in the sludge causes precipitation of phosphates or in strong oxidation systems in which phosphorus eliminated from the sludge stream), it is necessary to additionally add phosphorus to the Nutrition _t, and in such quantity that the carbon to Phosphorvex- ratio from about 100: is maintained. 1 The additional phosphate phor W may be added _t by phosphorus-containing compounds, for example, £ _r aliumdihydrogenphosphat adding "or by raw waste water or biological Dep added allschlamm from the main waste treatment process. The following examples illustrate the invention without, however, restricting it.

Example 1 Biotreatment of low pressure oxidation fluids

{A mixture of primary and biologically activated sludge was subjected to moist air oxidation at a pressure τ of 22.1 kg / fc cm ² and at 177 ° C for 55 minutes, so that 16.1 % of the organic material was oxidized. The mixture was then allowed to cool and sit for 4 hours and then the supernatant liquid was removed, which showed the following analysis:

BOD ^ 5.580 mg / liter

COD (chemical oxygen demand) 11,430 mg / liter.

The decanted liquid was continuously pumped at a constant rate of 605 liters / day in a temperature controlled 190 liter reactor, which was maintained at 56.1 ⁰ C. The residence time in the reactor was 7.5 hours, the leaktor was equipped with an immersed stirrer and a line, the evenly compressed air

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dispersed immediately under the stirrer.

The reactor had previously been filled with activated sludge and the lamb fluids were acclimatized, whereby one received a viable biological mass.

Air was introduced continuously at 31 liters per minute and 26 % of the oxygen in the air was absorbed by the biological solids. The resulting oxygen transfer coefficient EjSl was 139 mg oxygen transferred per hour per liter per mg / 1 dissolved oxygen deficit.

The biological sludge and fluids became continuous transferred from the reactor to a settled tank, where the solids of the sludge settle and from where they are transferred to the aerated Reactor were transferred. By removing some of the biological solids daily, the concentration became of solids in the reactor (mixture of volatile Liquid and suspended solids) kept at 4400 mg / l. The loading speed or loading amount was 4.28 kg BODc per day per kg mixture of volatile liquid and suspended solids, (mixed liquor volatile suspended solids).

The liquids that had settled and treated were continuously removed from the settling tank; where they streamed over a weir. The analysis of the liquids was:

BOD ₅ 276 mg / l

COD 3.870 mg / 1.

The reduction in the liquid was 95.1 % for BODc and 66.2% for COD. The new biological sludge that was produced was equivalent to 0.743 kg per kg of BODc removed from the fluids.

Example 2

Biotreatment of Heat Treated Liquids A mixture of primary and biologically activated sludge

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.... . ORiQlNAL {MSPHCTED

underwent heat treatment (no oxidation) at a pressure of 22.1 kg / cm and at a temperature of 177 ° C during a Subjected to time of 50 minutes.

After the mixture has cooled down and served for 4 hours, the supernatant liquid was decanted, which showed the following analysis:

BOD ₅ 3,200 mg / 1 COD 7,070 mg / 1.

The decanted liquids were pumped continuously at a constant rate of 269 liters / day in the reactor of Example 1 W / who had been previously filled with muddy water and acclimatized and this was maintained at 31.8 ⁰ C. The residence time in the reactor was 16.9 hours.

Air was introduced continuously at 6.8 liters / minute. Of the biological solids, 31% of the oxygen was in absorbs air. The resulting oxygen transfer coefficient K-j ^ a was 37.3 mg transferred oxygen per hour per Liters of dissolved oxygen deficit.

The biological sludge and fluids became continuous transferred from the reactor to a sedimentation tank, where the fc f solids of the sludge settle and from where they enter the reactor ; were recycled. Part of the biological solids was made removed daily, taking into account the concentration of suspended solids in the volatile liquid in the reactor 25OO mg / l held. The loading speed was 1.95 kg BODc per day per kg mixture of volatile liquid and. suspended solids.

The fluids that had been drained and treated were continuously removed from the settling tank and they showed the following analysis:

BOD ₅ 73 mg / 1

COD 1.010 mg / 1.

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In the liquid, the reduction in BODc was 97 »7 % in COD 85.7%. The formation of biological solids corresponded to 0.479 kg per kg of BOD removed from the liquids, -.

Example 3 Biotreatment of strong oxygenation fluids

(High Oxidation Liquors)

A mixture of primary and biologically activated sludge was subjected at a pressure of 127 kg / cm and at 260 ⁰ C for a period of 56 minutes, the wet air oxidation, so that 70% of the organic material was oxidized.

The mixture was allowed to cool and sit for 12 hours. The supernatant liquid was then decanted off, which showed the following analysis:

BODc 4,800 mg / l COD 8.430 mg / 1 phosphorus 21 mg / 1.

The decanted liquids were pumped continuously at a constant rate of 446 liters / day in the temperature controlled 190 liter reactor of Example 1 which was kept at 34- 3 ⁰ C. The residence time in the reactor was 10.2 hours. The reactor had previously been charged and the biological solids were acclimatized with the sludge oxidizing fluids.

To get the maximum metabolic rate of biological To maintain solids, the liquid did not contain enough phosphorus. Hence a solution of monobasic potassium phosphate (EHgPO ^) also continuously into the liquid, introduced into the reactor, the phosphorus content of the liquid was increased to 41 mg / l.

Air was introduced continuously at a rate of 19 liters / minute. 27 % of the oxygen in the air was absorbed by the biological solids. The emerging

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Oxygen transition coefficient iC ^ a was 103 mg oxygen, transferred per hour per liter per mg / 1 deficit of dissolved Oxygen.

The biological sludge and fluids were continuously transferred from the reactor to a settled tank where the sludge solids settled and from where they were recycled to the vented reactor. By removing some of the biological solids daily, the concentration of solids in the reactor (mixture of suspended solids and volatile liquid) was maintained at 4800 mg / l. The loading rate was 2.55 kg BOD _n per day per kg mixture of volatile liquid and suspended solid particles.

After the liquid was treated and drained, it was continuously removed from the settling tank and over a Weir headed. The analysis of the liquids amounts to:

BOD ₅ 34-5 mg / 1

COD 2.080 mg / 1.

In the liquid the reduction in BOD was 92.8% and in COD 75.5%. 0.333 kg of biological solids were obtained per kg BODc removed from the fluids.

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Claims (6)

Claims Λ ») Process for the biological treatment of liquids which is obtained" when dewatering thermally conditioned organic sludge solids, in which the liquids are introduced into an aeration tank which contains a previously acclimatized biological sludge, the mixture in the tank for a longer time is than 2 hours, with a gas containing oxygen, stirred until there is a level of dissolved oxygen sufficient to support aerobic biological growth, the mixture passes into a settling tank to separate accumulated biological sludge, the decanted biological sludge is recycled in the aeration tank and biological sludge is removed from the aeration tank at a rate approximately equivalent to the rate of accumulation of the biological sludge, characterized in that the liquids in the aeration tank are added without substantial dilution of the liquids with a Gesc rate between approximately 1.0 and 5.0 kg of biological oxygen demand per day per kg of mixture of volatile liquid and suspended solids. 2. The method according to claim 1, characterized in that phosphorus is additionally added to maximum biological To achieve growth rates such that the carbon to phosphorus ratio is approximately 100: 1. 3. The method according to claim 1 or 2, characterized in that that the temperature in the aeration tank is maintained in the range of 25 to 40 ° C. 4-. Method according to one of the preceding claims, characterized in that the temperature is controlled is by putting the waste heat in the thermally conditioned Exploiting the sludge by removing the fluids 109853/1302 are to be acted, brings in indirect heat exchange with the thermally conditioned sludge. 5. The method according to any one of claims 1 to 4-, characterized in that the liquid being processed is obtained by heat treatment of organic sludge. 6. The method according to any one of claims 1 to 4, characterized in that the liquid being processed is produced by moist air oxidation of organic sludge ψ will hold. 109 ^ 53/1302