Environmental Engineering Reference
In-Depth Information
• Illegal discharges from the industrial enterprises;
• Polluted runoff from the industrial areas;
• The excess use of fertilizers by informal small-scale farmers in the open ground area.
It has been mentioned that the water flow in the channel is perennial, thus the most likely
source of pollution could be associated with illegal discharges from the industrial areas.
The suggestion that phosphorous pollution could be associated with the practice of
informal agriculture is not likely, because these are small-scale activities practiced by
low-income residents as a form to complement their income.
6 CONCLUSIONS
Concerning the specific case study, diffuse pollution from urban drainage in the Lake
Chivero basin has been identified as a considerable source of pollution since the 1970's.
It is enhanced by the accelerated population growth, and overpopulated high-density
residential areas. However, it should be emphasized that the city's urban planning scheme
incorporates a considerable amount of developed and natural open ground spaces, which
act as a buffer and most probably, retain a considerable amount of the runoff pollution.
Also, it has a relatively well-developed infrastructure, which needs to be maintained and
operated in good condition. In general, the city has the potential for the implementation
of a proper diffuse pollution abatement program.
The existing regulatory arrangements provide the basis for an effective water quality
management but need additional improvements in order to control diffuse pollution
sources in a more effective way. However, the level of the monitoring programs, which
would back-up the enforcement of the regulations, is below standard, and do not provide
an efficient evaluation and detection of water quality. The control of diffuse pollution
sources would require a significant alteration of the existing practice, together with the
corresponding upgrading of the technical and human resources background.
Considering the specific catchment characteristics and the city's location, the major
causes for pollution of the Lake Chivero could be associated with polluted runoff from
the city's drainage systems, as well as with informal discharges from point sources of
pollution. This fact has been substantiated by the analysis of the monitoring data for the
period 1995-2000, which, despite the relatively inconsistent data set, shows a sustained
trend of increased nutrients concentrations, especially regarding phosphorous and
ammonia. DR1 has been identified as the contributor of the higher pollution
concentrations, compared to DR2, which could be associated with illegal discharges from
the industrial area drained. This finding points out the need of controlling not only
industrial discharges to the sewer system, but also to the drainage system, which should
be executed by local authorities.
Diffuse pollution in an urban environment, specific for the countries of the region, is
mainly associated with rapid population growth, which enhances the generation of diffuse
pollution in different ways - through the overloading of existing treatment facilities,
leading to unauthorized discharges of partially treated sewage, formation of informal
settlements and a general overcrowding of low-income residential areas. Diffuse
pollution pose a threat not only to the surface water quality, but also to ground water
quality. However, ground water quality has not been monitored at all, and in the vast
