Favela of the North-eastern District of São Paulo

Tietê is a Brazilian river which crosses São Paulo and is thrown in the Atlantic Ocean.
- Upstream of São Paulo, one takes there water for the daily consumption of the population and industries.
- Into São Paulo, the sewages are immediately rejected into the river, without preliminary treatments. Industrial worn water undergoes the same fate.
- In São Paulo and downstream, there are no more fish, more plants watery, more life, the river died.
In 1992, in front of the recrudescence of children born with malformations, an infant mortality rate and diseases abnormally high related to the quality of water, a petition largely relayed by the media succeeds in gathering a million signatures to make move the authorities.
The municipality is obliged to act quickly and gives rise to the Tietê project. Like made London with the Thames or Paris with the Seine, São Paulo wants to save its river and to enter a durable step of development.

The project was divided into three parts whose first is carried out right now. In this part the role of the SABESP, trust company of the water of São Paulo, is of primary importance since it puts a term at the pollution generated by the sewers of the city.
The rate of collection of worn water passed from 63 to 80% of 1992 to 1998 and in same time, the rate of water treatment passed from 20 to 60%.
The second part of the Tietê project envisages to increase the rate of water treatment of sewer with 90% and to extend the control of emission of effluents of industries.
This project is accompanied by a large public awareness campaign of the population to the saving in water as well as the organization of sessions of training of young people (for example of the water classes as on our premises...).
Here some figures concerning the SABESP and the city São Paulo:

SABESP in 2003

Investment :
The second phase represents 400 million dollars of investment, of which the half is dealt with by the SABESP and its financial partner which is the BNDES (banks of investment) and other half by the IBD (Inter American Bank of Development).
According to estimates' of the SABESP, within 20 years the river will be completely clean. Of aucuns say that it will take 30 years of them, it is long but the caused injury is very serious. One does not throw with impunity the sewers of 18 million people in a river!

Visit of a treatment plant of worn water

We visited the factory of Parks Novo Mundo inaugurated in June 1998 and which treats worn water of 1,200,000 people is 2500L/s
Because of the scarcity of space available to São Paulo, certain installations were modified compared to a traditional factory.

First stage: Oter large waste (having more 25mm)
This stage is led using a large grid periodically cleaned by a mechanical rake.

Second stage: Oter average waste (having more 0,76mm and less 25mm)
This stage is carried out in general in a first settling basin. Lack of space to conduit the SABESP to build 8 filters blocking this waste. The filters resemble large washing machines. Dirty water arrives directly inside the drum and leaves the drum through a filter. The waste retained by the grid of the drum is forwarded to outside by rotation of the drum. To avoid the bad smells the drums are closed, the air is aspired and treated in a special filter before being rejected.

Third stage: filtration of sand
The filter is composed of two large tanks (21m length, on 7m broad and 7m of depth) at the bottom of which sand contained in the water of the sewers settles. Periodically a system of crane empties collected sand. This stage makes it possible to avoid the wear of the equipment which would be caused by sand.

Fourth stage: basin of ventilation
Three tanks of ventilation of 25m broad are in place with an anaerobic part of 7,5m length provided with two mixers and an aerobic part (from where tank of ventilation) of 112,5m provided with a diffuser of air over all its length. The whole thus measures 120m and has a depth of 6m. The only goal of this ventilation is to increase the capacity of sedimentation of waste by limiting the growth of the filamentous bacteria (which prevents sedimentation).

Fifth stage: the secondary mud tank
They are six circular mud tanks of a diameter of 46m each one and 4m of depth (either a useful volume of 6650m3). Water arrives uninterrupted in the content of these basins and in fate by overflow. Gradually the suspended particles settle in the content of the basin and they are collected and evacuated towards the sixth stage. The water which overflows is disencumbered of a great part of its waste and is sent in the Tietê river or is recovered to be re-used.

Stages of treatment of muds.

First stage: concentration of muds
All the mud which remains in the content of the secondary mud tank, is pumped towards a well of 28m of diameter and 2m of depth (either a useful volume of 2450m3). Muds are concentrated there and must have solid contents of 4%.

Second chemical stage:Stabilisation and dehydration
An addition of iron lime and chlorate makes it possible to eliminate the pathogenic micro-organisms (bacteria, etc...) and to remove the odor of muds.
Traditionally this stage is made by anaerobic digestion, it is made here in a chemical way to limit space necessary.
Muds are then dehydrated in large presses which make it possible to obtain a product having solid contents of 30%.
After this mechanical dehydration mud is transported by truck in a factory which allows a thermal dehydration of these muds and transform them into granulated of 3 or 4mm having solid contents of 90%.

Other systems in place: Control and treatment of the odors
It acts mainly of hydrogen sulphite (H2S). The collected air is directed in a container where it is oxidized and neutralized by a solution of hypochlorite of sodium (NaOCl) and caustic Soda (NacOh). A detector of H2S makes it possible to check the complete abolition this gas in the exit air.

Where are muds sent?
Dehydrated muds are used as fertilizing phosphorus and nitrogen rich person. For the SABESP a good water treatment does not produce only waste, it produces also a useful and good product (note: or alleged like such) for the environment.
The dehydrated mud granules are analyzed in all the directions to check their effectiveness like fertilizer but also their hygienic quality.

Can water be re-used?
The water which leaves the station cannot be re-used like drinking water on the other hand, other uses are possible.
The slogan of the SABESP is as follows: "the re-use of water, an alternative of the present to guarantee our future".
After being treated, a part of the water of the factory is put in trucks and is re-used by the municipality and some industries for cleaning of the roadway system, of the vehicles, the cooling of industrial processes or the irrigation of the public grounds.
A part is even used to emerge the sewers (and yes that was done front, with drinking water…).

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First stage, one removes waste of more than 25mm.

Second stage, one removes waste smaller than 25mm...

...and larger than 0,76 thanks to this species of washing machine.

Third stage,

sand is removed

Fourth stage, one mixes water,

then it is aired.

Fifth stage, decantation. Mud settles in the content of the basin and is sent towards the pump which is in the center thanks to this enormous scraper.

"clean" water leaves by overflow the mud tank leaving the particles muds at the bottom. It is then recovered or will be thrown directly in Tietê.

Treatment of muds, in these basins of floating where are added caustic soda etl' hypochlorite of sodium.