污水排放海洋和垃圾处理——发展中国家遇到的问题

OCEAN OUTFALL AND SOLID WASTE DISPOSAL——APPRAISAL OF ENCOUNTERED PROBLEMS IN DEVELOPING COUNTRIES

随着社会迅速发展,人口密度不断增长,不可避免地产生了家庭废物的处理问题。某些发展中国家采用将垃圾倾入海中,填海筑路的办法,槟榔屿的情况就是这样。 拥有约50万人口的槟榔屿,从污水管排放出去的污水中约有60％是生活污水。这种污水多半未经处理就排放到西水道,再经过海洋下面0.8公里长的排水道。

Developing countries, while focussing to augment economical growth, have to face the problem of handling and processing the waste, viz., household garbage and sewage, of their ever increasing population at various intensified areas. In the Malaysian context, the municipality of Penang is an excellent example where household garbage is dumped at certain seaside areas with the objective of land reclamation despite primary sewage via oxidation pond processing system or an old ocean outfall was built some thirty years ago.Land reclamation via extensive garbage dumping at sites void of retention walls near shoreline areas of Penang evidently culminates in a diversity of environmental problems. The leaching effects during rainstorms and perpectual seep-leaching by adjacent fluctuating tidal ocean waters of heavy metals is of prime concern. Investigations have positively indicated such levels to be extremely higher than normal conditions, i.e. Cd by 3 X; 0.21 ppm, Co by 14.76 X. 0.93 ppm, Cu by 1.69 X. 0.11 ppm, Fe by 10.45 X; 1.16 ppm, Mn by 3.9 X, 0.25 ppm; Ni by 13.1 X; 2.33 ppm, Pb by 2.17 X, 0.65 ppm and Zn by 1.54 X; 0.04 ppm. Similarly, studies on the impact of the daily high input of organic matter, trace elements and nutrients by the Penang ocean outfall into the tidal fluxed area of the Western Channel of selected bioindicator aquatic organisms in its vicinity were quite unfavourable. Comparison of bioaccumulated trace elements in the sedentary green-lipped mussel, Perna viridis L., with those of other areas indicated levels of Co to be higher by 2.94 X; 25.98 ppm, Cr by 11.9 X; 11.91 ppm, Cu by 12.38 ppm, Fe by 7.99 X, 2166.33 ppm, Mn by 6.24 X; 75.15 ppm, Ni by 4.32 X; 81.21 ppm and Pb by 2,96 X; 21.04 ppm. In the same context, juveniles of the finfish, Liza subviridis L., reflected Cd to be higher by 2.6 X; 2.6 ppm, Co by 56 X; 56.0 ppm, Cr by 18.9 X; 18.9 ppm, Cu by 34.3 X; 34.4 ppm, Fe by 1233.59 X; 2713.9 ppm, Mn by 33.8 X; 38.8 ppm, Ni by 118.5 X; 118.5 ppm, Pb by 1063 X; 106.3 ppm and Zn by 65.66 X; 269.2 ppm.Obviously, this indicates that on a long-term basis it will have a great impact on the marine food web culminating in devastating effects on human health.Due to periodic outbreaks of gastrointestinal infections around this region, the concentrations of coliforms and Escherichia coli of the raw untreated sewage at the final point of discharge at the ocean outfall system was also monitored. To ascertain the degree of bacterial contamination the total number of bacteria as well as spore formers was also performed. High levels of coliform; 4.9×107, E.coli; 1.6×107, total aerobic counts, 1.3×108 and total spore formers; 3.8×108 were observed.The other aspect of the sewage outfall is the problem associated with parasitic diseases. These include both protozoan and helminthic infection which has undoubtedly a great bearing on the health and soeioeeonomic level of rural people. Hence, investigations in this area on the role in the transmission of related soil transmitted helminths and other protozoans revealed the presence of Ascaris lumbricoides, Trichurus trichura hook worm, Toxocara canis viable eggs and amoeba. Based on these data the possible role on the source of infection is also discussed.Evidently, the present ocean outfall for sewage treatment and garbage land reclamation method are in no way beneficial to our community as a whole from the viewpoint of public health. It is recommended that a proper tertiary sewage treatment plant and garbage incineration or compost treatment plant be planned for the municipality of Penang.