OPPORTUNITIES AND CONSTRAINTS FOR BIOREMEDIATION OF SOILS: THE MEXICAN CASE

José Luis Solleiro, Rosario Castañón and Rodolfo Quintero

Universidad Nacional Autónoma de México (UNAM), Apartado postal 20-103, 01000 México, D.F.

For several years, the participation of the present productive system in the generation of polluting products and their negative impact on the environment have been in the process of evaluation. There is an international consensus as to the need to modify industrial processes in order to decrease the generation of toxic effluents and/or effluents of a polluting character, to increase the recycling of waste, to improve efficiency in transformation and, in all cases, to seek sustainable development for the middle and long term which will respect and preserve the environment while helping to reclaim places that have already been polluted.

There is, at present, in Mexico great interest in decreasing the pollution generated by the productive sector and society in general, while, in turn attempting to preserve and restore the environment. This obeys three main factors:

1) In the 1960's a law was passed concerning the environment and its conservation, but it was only six years ago (Table 1) that the government decided to implement it by establishing the respective norms and regulations and economic penalties for those who breached them.

2) Mexican society as a whole has shown great concern over the pollution indices in the industrial and some urban zones, as well as in agricultural regions where chemical pesticides have been

used for many years, and have recognized that it is necessary to generate policies and measures to decrease and, if possible, eliminate pollution.

3) International trade has stipulated the need to produce by means of less polluting processes. In this sense, there is a threat that several Mexican products may not be accepted abroad or that some sanction might be imposed if they are not produced with the available clean technologies.

As a result, there has been a large demand for innovative technologies involving cleanliness and environmental rehabilitation. In one of these technologies, a growing number of microorganisms and their extracellular products are being used in processes known as bio-remediation that are employed in the treatment of sewage and in soils contaminated by chemical products - hydrocarbons and/or chemical pesticides. At the same time, preventive measures are being taken to minimize the production or generation of pollutants in industrial processes. Bio-remediation presents optimistic perspectives and is an important strategy in the elimination of organic waste (hydrocarbons, herbicides, pesticides and agrochemicals among others).

There are three main sources of environmental pollution that can be treated by biological procedures in order to eliminate them and/or at least decrease their incidence:

Urban sewage (organic material and toxic compounds) Sewage (of municipal and industrial origin)

Toxic waste (from industrial processing and agricultural use)

Sources of pollution can be found all over the country in urban areas, agricultural zones and in places bordering on industrial centers. Some industrial sectors that generate pollutants have become extremely relevant since they have established specific norms and regulations restricting the discharge of pollutants and establishing the maximum levels permitted. As there is political and social pressure they have become a very important potential market. It is estimated that US$50,000 million will be required over the next five years to restore the environment in Mexico.

Bio-remediation, technologically, presents an excellent option, at a world level for the treatment of waste with a high content of organic material. This, together with the environmental problems of Mexico, has been a factor motivating the study of business opportunities in the area.

Organic pollutants found in soils are a major focus, because, according to several experts, there are, at present, serious problems with pollution in this field (Table 2); large companies are interested in treating the affected areas; and very few firms have adequate technologies. In other words, there is large potential demand for services and little supply.

The area of sewage treatment is, without doubt, a sector that has experienced growing development over the past few years and also offers many opportunities; however, for the same reason, it is an area in which there is a great deal of competition. The following facts can be mentioned, for example, in 1993, 70 new enterprises were established, many of which are partnerships with foreign companies; it is calculated that only 12% of sewage is treated (almost 200 m³ a second); another fact that indicates the size of the market is that only on the northern border of Mexico with the United States are sewerage plants being established with a value of 3,000 million dollars, while it is estimated that the national market is in the order of 1,000 million dollars a year in plant investment alone. Other potential market indicators for sewage treatment are presented in Annex 3.

The generation of both non-toxic (garbage) and dangerous (industrial waste) solid waste is calculated to be 422,000 tons a day, 14,500 tons of which are dangerous waste. It should be pointed out that even when there is a great deal of interest in eliminating toxic waste, there is very little information available, no quantification of volume and, in many cases, the identification of particular pollutants is incomplete or non-existent. However, if we make an analogy with what has happened with the treatment of sewage, we can suppose that bio-remediation applied to soils is a developing area and there is great market potential.

Possibilities that exist for applying biological techniques to the reclaiming of soils polluted by organic compounds can be divided into three main groups:

Soil polluted by oil and by-products

Agricultural land polluted by agrochemicals

Soils polluted by industrial waste (paper and cellulose industry, generation of electrical energy, etc.)

In Mexico, the petroleum industry as a whole has had a far reaching, negative impact on the environment. Due to the broad spectrum of oil by-products it has not been possible to quantitatively evaluate total discharges, from the exploitation phase to the production of basic petrochemicals. However, since oil and its principal components are biodegradable, there is a great deal of industrial and research interest in generating technologies that can recover spills of crude oil and of other petrochemicals considered to be pollutants.

There are several sources of pollution from oil. At a world level, it is calculated that between 5 and 10 million tons of hydrocarbons go into the oceans each year; of this amount, almost 45% is due to the handling of oil at sea (including accidents) and 37% comes from industrial outlets and urban waste. Only 2% is due to exploitation and production.

There are also chronic leakage's in refineries, in internal transport and process water. In primary production, pollution problems are generated by activities in separation batteries, dehydration plants, wells and accidental leaks through breaks in the lines. The waste, on the whole, goes into bodies of water and rivers as well as into agricultural land.

Various strategies have been applied to contain and recover hydrocarbon spills including physical procedures (adsorption, reservoirs, evaporation, etc.), chemical procedures (dispersion, coagulation) and biological ones. There has recently been a great deal of interest in using bio-remediation to quickly decrease and attenuate the ecological impact produced by high concentrations of petroleum near coastal areas, and also in reclaiming soils that have been polluted during the extraction and processing of oil on land, since the hydrocarbons are swept along in the water and reach water deposits destined for urban use with the well-known risks to human health.

Legislation and regulations for the oil industry and for soil in general are in their early stages, but in the particular case of petroleum, the parastatal company responsible for exploitation, Petróleos Mexicanos (PEMEX), is interested in reclaiming polluted soil. The market is therefore presented as viable, and to be developed, although it must be pointed out that the problem has not been quantified and it is not known in detail what the principal pollutants are.

In other industrial sectors, although bio-remediation can also be used potentially, it is not possible to indicate when activities will begin in the fight against pollution. Although the problem of pollution exists in the agricultural sector and there is a wish to remedy it, it is recognized that its distribution throughout the country and the land tenure problem makes this difficult.

Finally, it is important to point out that in order to carry out this study, various sources of information were consulted, both official information and information from independent institutions. Similarly, data and recommendations given during interviews by various experts on the subject were included.

This talk is based on a study carried out by Grupo Assestec, S.C. with the participation of Rosario Castañón, Rodolfo Quintero, José Luis Solleiro, and Hilda Hernández.