Waste Water Treatment Plant Process in Chennai
Waste Water Treatment Plant process in Chennai includes a classic pre-treatment unit with a preliminary coarse screening followed by fine sieving for the whole of the throughput. The separation process continues with the effluent being directed to the dry weather biological channel up to a flow of 8.2 cubic meters/sec. The excess flow is directed to the wet weather channel to a maximum of 16.4 cubic meters/sec.
b) Biological treatment
The dry weather flow is sent to grit and oil removal before being processed in 12 biological treatment channels. Each of these channels has first a biological degrading zone for phosphorus, followed by one for carbon and nitrogen (AZENIT-P® process( cfr section 6)). The effluent is then sent to basins where the treated water is clarified through decantation of the biological mud. Part of the decanted sludge is sent back to the start of the treatment process to be fed into the biomass. The clarified water is sent out to be returned to the Senne. Waste Water Treatment Plant process in India is very quick now a days.
c) Wet weather treatment
Wet weather is characterized by a re-suspension of the solid material that had sedimented in the network through dry weather. The treatment of this sewage requires specific techniques.
The wet weather flow is first sent through a rough grit removal to eliminate particles bigger than 300 micrometers (MECTAN® process). Then it is settled using the ACTIFLO® process (cfr section 6). This rapid settling technique involves lumping the effluent together using a coagulant and then mixing it with sand. With its high density, the sand speeds up the separation out of the agglomerate in the decantation stage.
d) Sludge Treatment
The principle is to break down the organic material in the sludge so as to obtain an entirely mineral final residue. This break-down process uses two complementary procedures: digestion in the anaerobic phase and wet oxidation.
- Preliminary conditioning
After exiting the water treatment stage, the sludge is first thickened in cylindrical structures in each of the process lines, both biological and wet weather.
The sludge is conditioned with a polymer to facilitate decanting before it is guided into the structures.
The sludge is then extracted and pumped into a common storage area in preparation for dehydration. This is done using centrifuges. Four treatment lines with one as back up are planned for this stage. After dewatering, the resulting residue is stored in a silo for the next stage.
- Digestion in the anaerobic phase
Digesting the sludge eliminates the fermentable organic material that in particular generates odours.
Degradation is achieved in an anaerobic atmosphere (i.e., without oxygen) by two fermentation pathways, acidic and mechanic, each of which using distinct bacteria groups.
Acid fermentation transforms the organic material into soluble compounds, essential fatty acids, and alcohol. This also produces carbon dioxide.
Mechanic fermentation products mostly methane and a lesser quantity of Carbone dioxide by further degradation of the soluble compounds.
Methane produced by the digestion process is recovered then stored in gasometers. It will be burned to produce vapour that to be used in the process and hot water that can be used for heating the space.
It is planned to put a thermic hydrolysis unit upstream of the digestion stage, first to liquefy the sludge and secondly to break down the longest molecular chains. The resulting mixture becomes much more easily assimilable by the digesting bacteria – “turbo-digestion”.
This thermolysis process (CAMBI®) runs at 165 °C at 8 bars pressure after the centrifuged sludge is mixed with the greases from the oil removal treatment in the biological line. Five reactors are used to do the hydrolysis.
The residue obtained, after cooling, is introduced at the digestion stages. Two structures are planned for Brussels-North, each of them equipped with a mechanical agitation system for the liquefied sludge.
On exiting the digestion stage, the sludge is directed to the oxidation unit.
Waste Water Treatment Plant process in Chennai is the very first growing industry right now. Produced biogas is evacuated for storage in gasometers. It can be used for the production of both vapour (hydrolysis thermal and wet oxidation) and hot water (heating of the buildings).
- Wet oxidation
The anaerobic phase digestion process does not completely remove all organic components in the sludge. This mineralization is achieved using a complementary oxidation process.
This is done by bringing the liquid sludge into contact with oxygen at 50 bars pressure and 250 °C, which allows higher kinetic interaction.
Two treatment lines each with an oxidizing reactor are planned for the Brussels-North plant.
This process has been used for treating industrial sludge for more than 20 years, and its more generalized application for urban sludge has created the ATHOS® system ( CFR section 6).
The nature of the resultant gas products from this process sets this system apart from incineration. Furthermore, this process does not produce dioxins.
- Final conditioning
After cooling, the reactional mixture is sent to a lamellar decanter to separate the solid and liquid parts. The liquid obtained after separation contains acetic acids, aldehydes, and ketones.
All these biodegradable components will be recycled within the plant. The solid residue is dried on a filter press.
b) Devolution of the final residue
The preferred destination of the residual mineral product is sanitary landfill as communal waste.
In effect, the non-lixiviable nature of the compound obtained will allow permanent storage of the same sort as for incineration residues such as clinker and ash.
Since the daily discharge will be considerably less than that of a classic plant, the pollution associated with the cartage of the residue is minimized.
This residue material could also be used in infrastructure projects.
The mineral and sandy nature of the compound could allow its use as follows:
- for road under-bedding;
- for brick-making;
- as extra material in cement fabrication.
e. Air treatment
All the plant is enclosed within the building, and all the air is treated.
a) Chemical treatment of effluent
The principle of the AQUILAIR® process ( CFR section 6) that is used, is to “wash” the gas with the aid of aqueous solutions to which the odorant gaseous molecules are transferred. For this to happen, the effluent runs in contra-flow through a set of towers connected in series, each containing a washing solution.
Three treatment lines, each with two towers, will be installed at Brussels-North:
the first of the two towers will have an acid wash;
the second will have a basic wash.
b) Biological treatment
The ALIZAIR® process ( CFR section 6) used is a biological deodorizing process that uses biofiltration techniques.
The principle is to pass the gaseous effluent across a bed of bacteria where the malodorous molecules are degraded through oxidation. The bed is continually sprayed with a mixture of water and nutritional elements to maintain bacterial activity.
The water being sprayed absorbs the products of oxidation as it passes through the bacteria bed. It is then sent to the biological facility for treatment. The choice of filtration material depends on the composition of the effluent.
Major process benefits
- High treatment efficiency; removal rate of turbidity > 90%
- Very small footprint compared to conventional clarifiers; suited for restricted spaces and easy retrofit of existing plants
- Reduced civil engineering
- Flexible: reacts quickly to changing raw water quality; provides consistently high-quality effluent
- Very short start-up time < 10 minutes
- The sludge produced can be thickened and dewatered easily
- Can be entirely automated and remotely controlled
- Minimum equipment to maintain, all easily accessible 15 years of operating experience with more than 300 Actiflo™ references worldwide
- Prefabricated package plants (1 000 to 10 000 m3/d per unit) which can be combined for larger flow rates