Environmental Biotechnology - Theory and Application

Aerobes and Effluents 139

forms of solid waste, a proportion have been consigned to either landfill or
incineration. For some treated sludges, especially those derived from domestic
sewage or food residuals, agricultural use has been an option, often requiring
additional treatments to ensure its freedom from human pathogens, before land
spreading or injection beneath the surface. The effectiveness of microbes in metal
sequestration means, inevitably, that most treated sludges have a degree of heavy
metal contamination, which itself makes possible the accumulation of these con-
taminants in soils exposed to these products. In addition, there are increasingly
stringent controls on the release of nitrogen to the environment, particularly
within escalating European Union legislation regarding nitrogen vulnerable zones.
It would seem, then, that the future land use of ‘spent’ sludges is likely to be
somewhat more heavily regulated than previously.

Closing Remarks

In many respects, the treatment of effluents by biological means is of particular
importance to any consideration of environmental biotechnology, since it repre-
sents the central point of the previously mentioned intervention triangle, having
simultaneous relevance to manufacturing, waste management and pollution con-
trol. The majority of manufacturing companies produce wastewaters that contain
organic contaminants of one form or another and the traditional route previ-
ously in common use: discharge to sewer, watercourse or the sea, is becoming
less attractive due to environmental legislation and rising disposal costs. As a
result, for an increasing number of companies there is a growing requirement to
treat their own effluents and biotechnological processes can often prove the most
cost-effective means to achieve this goal.

References

European Commission’s Directorate General for Environment, (2001)Survey of
Wastes Spread on Land – Final Report, Office for Official Publications of the
European Communities, Luxembourg: (a) p. 2; (b) p. 55.
Hardman, D., McEldowney, S. and Waite, S. (1994) Pollution: Ecology and
Bioreatment, Longman, Essex: pp. 81–2.

Case Study 6.1 Mollusc Biofilters (Rhode Island, USA)

Maintaining or improving the quality of coastal water, particularly around areas of

high tourist or amenity value is an increasing concern in many parts of the world.

While restricting polluting discharges at their source remains the ideal solution to

the problem, various biological interventions have been suggested to deal with the

problem directly and the potential of some of these may be developed in future years.

Continued on page 140