Decentralized wastewater treatment: The example of the Brazilian city Piracicaba – Adaptation of processes to subtropical countries

The water quality of the Piracicaba will be improved by treating the wastewater in decentralised, modern treatment plants before discharge into the river.
Figure 1: The water quality of the Piracicaba is to be improved by treating the wastewater in decentralised, modern treatment plants before it is discharged into the river.

South American countries have an enormous need of well functioning wastewater purification systems, particularly in the densely populated regions, in view of the environmental problems. The statutory framework is in many cases already in place, but the implementation is missing, which in the majority of cases founders at financial hurdles. Consequently, at the present time, just 10 percent of wastewater in the major South-American cities goes for treatment. This results in massive enormous pollution of lakes and rivers, and limitations on water supply (Fig. 1). As an alternative to large, expensive, centralized treatment plants, decentralized solutions are being considered in many cases.

Cooperation project in Piracicaba

 View of a decentralised sewage treatment plant with a near-natural process.
Figure 2: View of a decentralised sewage treatment plant with a near-natural process. Disadvantages, especially for urban structures, are the large space requirement of the pond treatment plant and the occasional odour nuisance due to overloading.

Piracicaba, a city with a population of 320,000 in São Paulo State, Brazil, has at any rate 35 percent connection to wastewater treatment systems. The city is pursuing ambitious plans, and aims by 2007 to have all its inhabitants hooked up to treatment plants. The municipal concerns responsible for water supply and disposal decided in years gone by to erect a large number of relatively small treatment plants in the urban area. In the majority of cases they adopted conventional decentralized solutions, which were developed more for the rural region (Fig. 2). That decision has now resulted in a number of problems, the solutions to which are being sought in cooperation with the Fraunhofer IGB.

Evaluating the treatment plants, with corresponding measurement programs, represents the first step in a cooperative venture between the Brazilian and the German partners in a project assisted financially by the German Ministry for Education and Research (BMBF).

Decentralized wastewater treatment for densely populated urban structures

With future treatment plants, new concepts are to be followed, which effectively treat wastewater to remove organic substances in closed systems, coupled with energy recovery and /or recycling of nutrients like phosphorus and nitrogen.
The statutory provisions governing treatment plant discharges in Brazil are relatively stringent, particularly as regards emissions of disease pathogenic microorganisms. In order to avoid aerosols and odors, the plants are to be closed systems and must include further treatment of the outlet of the plant so that, in a sustainable water management concept, the treated wastewater can be used as service water. Great importance is attached to processes which operate with low sludge levels, in order to minimize or avoid disposal problems. The Fraunhofer IGB has already begun with investigations in Germany and has established the necessary contacts on site.

Modern pilot plants

In Piracicaba, gradually, small, self-contained neighborhoods are being set up, which require connection to a treatment plant. Decentralized solutions are particularly well suited to this kind of situation. A number of plants are to go into operation on the site occupied by a university to show how digestion of organic wastes works in the developed process and as well as effective treatment of the wastewaters, while also taking account of possibilities for appropriate rainwater management.

Also under discussion as a site for a model treatment plant is a district of the city that is earmarked for high tourist expansion. The utilization of water, heat and energy looks to be a good possibility, with minimal expense, and will convince both users and visitors to the plant as a whole of the benefits of innovative processes.