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5.5 Wastewater disposal (Topic e)

The unmet needs of wastewater and excreta disposal in Latin America and the Caribbean were estimated in 1988 at 162 million people lacking adequate means of disposal, 73 million in the urban areas and 89 million in rural areas. By the end of 1995 and based on figures provided by those countries, the total unmet needs were 145 million, 67 million in urban areas and 78 million in rural areas. Data for the end of the 1990's ("the lost Decade" is still being collected but given the economic crisis that has swept the Region it is likely that the demand figures have increased once again.

For the most part, the lack of infrastructure for water supply and sanitation services was blamed for the resurgence of cholera in Latin America. One of the most critical sanitary problems in Latin America remains the lack of sewage treatment and/or adequate disposal sites. Untreated (raw) and inadequately treated sewage have contaminated surface and groundwater. The contamination of groundwater by nitrate from raw sewage has caused a large number of water producing wells to be abandoned. The situation is no better even for cities that possess final disposal outlets because lack of maintenance has put most of the systems in environmental jeopardy.

The effectiveness of existing disposal facilities in the Region is usually constrained by limited capacity, poor maintenance, process malfunction, poor maintenance practices, and lack of experienced or properly trained staff. Most collection and treatment facilities dispose of their effluent and wastes directly into the closest receiving water body, which soon exhibits high coliform concentrations and low dissolved oxygen levels.

In rural areas of the Region, collection systems are rarely used, and pit privies and latrines are the most common waste disposal systems. These processes can be most effective, provided they are designed, installed, maintained, and used properly. The biggest problem with them, nevertheless, is lack of maintenance. Pit latrines, and pit privies need to be desludged periodically. Failure to desludge has resulted in contamination of the environment.
In areas of higher population density, it is feasible to develop a local collection system and use a single facility to treat the community’s wastes. Lagoons, stabilisation ponds, and aerobic package plants are common and useful treatment options for medium-sized communities in the Region, except that effluent control practices are weak and therefore a lot of these units have been reported to be operated poorly.

In centralised, urban centres, lagoons, package plants, and conventional activated sludge systems are used. Many of these treatment facilities do not provide adequate treatment because of improper maintenance, and lack of skilled operators. Similar problems happen with the operation of marine outfalls.

General problems that affect sewage disposal in the Region may be summarized as follows:

• Lack of knowledge by the people, especially the poor, of the existence of a clear link between foul waste disposal and public health diseases. Environmental and sanitary education are topics still to be conveyed to people, yet are required for further practical actions to be taken by a large portion of the Regional population. People from low-income areas quite often do not rank as a priority of Governments for the implementation of adequate waste disposal facilities in their communities and usually do not demand their Governments to change their ranking.
• Culturally speaking there is “common understanding’Ein the Region that as wastewater facilities are not part of the ordinary infrastructure package, when they exist they may be offered free of tariffs.
• Weak political backing by governments, relevant sectoral agencies and even NGO‘s towards the enforcement of environmental policies to guide sewage disposal and the implementation of adequate sewage disposal services.
• Financing of wastewater facilities has been neglected by sectoral agencies and even by multilateral agencies which have used money allocated to wastewater works to cover inefficiencies of the water sector.
• The lack of dissemination of alternative, lower cost measures/facilities that might contribute to improve the economic/financial feasibility of waste disposal systems.

A lot of projects handling wastewater disposal from medium and large sized areas have been poorly designed mainly because there is a poor understanding of what measures need to be taken to protect the environmental values of receiving waters. Generally speaking, very little in the Region, to say the least, has been discussed regarding the adequate sewage treatment and disposal option that may restore environmental conditions now damaged by foul waste disposal. Activated sludge (and other BOD reduction alternatives) has been considered to be the default option even for coastal areas where, for instance, the post-treatment/disposal bathing conditions must be the environmental indicators.

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