FR2464996A1 - Improving efficiency of e.g. activated sludge treatment - comprises using terra cotta particles as support for micro organisms - Google Patents

Abstract

A method of enhancing the efficiency of biological processes, esp. a process in which activated sludge is employed for the purificn. of waste water. The process comprises fixing active micro-organisms on a porous support which is contacted with a fluid to be treated. Particles of terra-cotta are used as the support, the particles having an ave. dia. of 20-200 microns, pref. 40-80 microns. The proportion of particles introduced into the medium to be processed is between 2 and 50 kg per cubic metre, pref. between 5 and 20 kg. per cubic metre. The type of terra cotta material is pref. (a) kaolin porcelain with undoped surface. (b) terra cotta with its surface doped with strongly electro-positive chemicals. or (c) a mixt. of terra cotta and activated carbon particles. Used for biological treatment of liq. esp. purificn. of waste water with activated sludge. Also clarification of beer wine and pharmaceutical prods. Increases the treatment capacity of biological processes.

Description

 The present invention relates to the field of biological treatments in the process of which a medium is brought into contact with bacteria or microorganisms in order to ensure various transformations of this medium. It relates more particularly to a process making it possible to increase the yield of biological processes, by fixing on a support of non-immobilized microorganisms.

It is known that the use of various supports, for example oxides or a mixture of generally porous metal oxides, makes it possible to promote the attachment and the development of microorganisms in biological processes. This is the case in particular of biological transformations by enzymatic systems, preferably on immobilized supports, or also of all other processes involving bacteria, yeasts or other microorganisms in a mobile medium for the purpose of purification and / or clarification, such as for example in the beer, wine, pharmaceutical, etc. industries.

Among these applications, one of them is particularly important and relates to the treatment of water and especially the biological purification of water by the process known as activated sludge where one causes and maintains within a current waste water a homogeneous mass of flakes of mucilaginous matter or biomass in which live microorganisms, aerobic or anaerobic bacteria, protozoa ..., which degrade the organic matter contained in waste water and transform it by assimilating it to the biomass which is capable of decanting when it is in a current at low speed.

It has now been found that when a free biomass, such as an aerobic treatment activation basin or an anaerobic digester for wastewater, is introduced, certain supports in the form of very fine powder, one obtains, among other advantages , a dramatic improvement in the efficiency of microorganisms and therefore in treatment facilities.

 According to the process of the invention, a baked clay (commonly called "chamotte") is introduced into the non-fixed biomass in the form of impalpable particles with an average diameter of between 20 and 200 microns and, more advantageously still, in the range of 40 at 80 microns.

 The quantities of cooked clay to be introduced depend on the characteristic parameters of the environment, for example, in the case of used water, the type of pollution and the quantity of activated sludge.

Generally, these quantities are of the order of 2 to 50 kg / m 3 of apparatus and are most advantageously between 5 and 20 kg / 3 m.

 Chamotte or baked clay is a very old material (falling into the more general category of ceramics) obtained by calcination of various clays and traditionally used for its refractory properties. In recent years, however, new routes of use have been opened thanks to the development of cooked clay aggregates capable of serving as supports in chemical or biological medium. This is why we recommended the use of cooked clays, simple or doped with various metallic elements or mixed materials carbon-active-chamotte, as bacterial supports for the biological treatment of water (see for example the French patents or patent applications n076.03573, 78.22779, 79.15632 and 79.18554).

 When a doped clay is used in the context of the invention, the latter can be obtained according to any of the known methods. For example, one can add the metallic element (s) - such as those listed in the aforementioned patents - to a natural clay of the type: illitic, kaolinic, halloysitic, montmorillonitic or mixtures of these products. The addition can be carried out either in a humid environment or by the dry route, the chamotte recovered after cooking around 1200-13000C then being ground and sieved to the fine particle sizes mentioned above.

The use of a fine chamotte powder in a biomass provides many advantages, among which we must cite, for example the case of water treatment: a sharp increase in the concentration of microorganisms in the aerator or the digester, therefore a increased purification efficiency; easier decantation because the chamotte particles are surrounded by large flocs, which makes separation in the clarifiers easier; markedly improved drying, which favors the subsequent conditioning of sludge.

 In order to illustrate the interest and the effectiveness of the process of the invention, the results of comparative tests carried out in the field of biological water treatment will be briefly described below.

Example
The influence of the addition of fine chamotte particles on the purification yield as a function of the volume charge introduced has been studied in a system comprising two conventional sets for studying activated sludge and in particular comprising an aeration tank. and a secondary decanter with recycling of sludge in the tank.

Before testing, we seeded the two sets
or circuits by circulating for 2 days in a closed circuit
lange of drinking water and activated sludge. Then we introduced small
gradually synthetic substrate balanced in nitrogen and phosphorus while
gradually removing excess sludge.

After a week, the system being stabilized, we proceeded
the introduction into one of the two circuits of a BIO type chamotte
GROG L (registered trademark), size, average particle size: 50 to 80
microns, at a rate of 5 grams per liter of liquid to be treated.

After two days, the pollution measurements were made at the entrance and
at the exit of the two circuits.

The results obtained are reproduced on the curve of the fi
gure 1 appended where the abscissa indicates the volume load in kg per day 3
and by m while the ordinate corresponds to the purification efficiency in Z.

Curve (A) corresponds to the tests carried out in the presence of chamotte
according to the invention while the curve (B) refers to the control test.

As we can see, the purification yields are remarkable
improved in the presence of fine particles of baked clay and increased
try more and more according to the increase in the charge
mique.

The chamotte used was of the kaolihique type, undoped and with
high porosity (40 Z) of the following composition
Al203 .. 54.3
SiO2 4193 Fe203 000 1.9
Ti02 ........ 1.4
alkaline 0.7
alkaline earth 0.1
Tests carried out with other types of chamottes, doped or not, have given substantially equivalent results in increasing the purification efficiency by comparison with conventional systems for treating water by activated sludge.

 Furthermore, although described above for the purification of water, the same process can be used in other biological processes where microorganisms such as bacteria or yeasts are used without immobilization in a liquid medium, such as for example in the beverage industries: beers, wines .. and in the pharmaceutical industries.

Claims (5)

 1. Process for increasing the yield of biological processes by fixing on a support of microorganisms not immobilized in the said biological process, characterized in that a baked clay (or chamotte) is used as support in the form of particles of average diameter between 20 and 200 microns.  2. Method according to claim 1, characterized between the diameter of the particles is between 40 and 80 microns.  3. Method according to any one of claims 1 or 2, characterized in that the quantities of chamotte introduced into the medium are between 2 and 50 kg / m3 and preferably 5 and 20 kg / m3. 4. Method according to any one of claims 1 to 3, characterized in that the chamotte is chosen from the group of conventional non-doped kaolinic chamottes or from that of cooked clays with a highly electropositive surface such as chamottes doped with chemical elements very electropositive or in that of mixed materials: chamottes-activated carbon. 5. Application of the method according to any one of claims 1 to 4 to the biological purification of water by activated sludge and to the treatment of all liquids in contact with microorganisms not immobilized on supports.