POTENTIAL POLLUTANTS, THEIR SOURCES AND THEIR IMPACTS
1.1 Contamination or pollution
It is amazing how many people seem to live alongside serious pollution and not notice it. Fishery harbours and landing places around the world have traditionally been regarded as 'appropriate for insanitary conditions'. Only in the recent past has it been recognized that it is feasible to maintain clean fishery harbours provided special care is taken proactively
Fishery harbours must accommodate the special needs for (a) water supply and (b) management of solid/liquid wastes. Insanitary conditions not only result in degradation of the environment, but also in contamination of fish and rapid spoilage. They also pose serious health hazards such as typhoid, cholera, hepatitis-B, and gastro-enteritis
What is contamination? What is pollution? These are terms that need a clear definition
GESAMP (Joint Group of Experts on the Scientific Aspects of Marine Pollution) defines pollution as the introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to marine activities including fishing, impairment of quality for use of sea water and reduction of amenities
Contamination on the other hand is the presence of elevated concentrations of substances in the environment above the natural background level for the area and for the organism
Contamination of water by physical and bacteriological agents, be it drinking water, ice water or harbour water, may be evaluated by laboratory tests. Test results are usually expressed in parts per million (milligrams per litre or simply ppm) or parts per billion (micrograms per litre or ppb) for physical parameters; and bacterial counts per 100 millilitres for organisms. For both types of contaminant, maximum levels are usually stipulated and these levels may differ from country to country
1.2 Contamination of water in fishery harbours
Contaminants in modest quantities are present even in clean aquatic environments. A few metals such as copper, selenium, iron and zinc are essential nutrients for fish and shellfish. Contamination occurs when there is a significant increase in their levels. Problems related to chemical contamination of the aquatic environment are nearly all man-made. Industrial effluents, sludge from sewage treatment plants, agriculture run-offs and raw untreated sewage from urban populations and industry-all these contribute to chemical contamination of the environment
The main concern of harbour managers however, is that clean water chemically equivalent to drinking water is needed for fish washing, ice making and fish processing. Many chemicals present above a certain level in water can be a public health hazard. Some interfere with water treatment processes, some stain fixtures and plumbing, a few may cause undesirable scaling and may be aesthetically objectionable
Due to the acute shortage of potable water in many countries, raw sea water is often utilized during fish handling at sea or in port. This means that in addition to tap water, harbour basin or estuarine waters could be a potential source of contamination
Pollution of harbour waters due to dumping of untreated sewage in contiguous waters and the harbour basin, is often the most common cause for seafood-related diseases and epidemics
But it is a matter for concern that harbour water quality is heavily influenced by human activity not only within the harbour complex but in the surrounding environment as well. Effluents from aquaculture ponds, agriculture runoff, sewage discharge, toxic effluents from industry into the contiguous water body, all affect the marine environment through biological, chemical and physical interactions over different temporal and spatial scales. In addition there may be impacts that arise as a consequence of accidents or failure of normal operations such as oil spills in coastal waters
The fishing harbour is the focal point of the fishing effort (and sometimes village life revolves around the activities of the harbour). It is here that fish is likely to be contaminated. By charting the flow of fish through the fishing harbour (from the time it is discharged on the quay to the time it leaves the port boundary), points can be identified where contamination or growth of micro-organisms occurs. Control features can then be implemented, based on the identified health hazard. This technique is known as a Hazard Analysis Critical Control Point programme or HACCP in short. To the fishing port manager, the three major areas of concern are
1. Water quality standards of all the water used in the port (potable and sea water)
2. Personal hygiene of the shore-based workers
3. Standard of cleanliness of the port in general
Under HACCP, these three areas of concern translate into drastic changes in the long-term. In particular, these involve
· Minimising and eventually eliminating harbour and coastal pollution from point and non-point sources
· Improving sanitation and hygiene throughout the fishing harbour
· Maintaining port and harbour infrastructure in good working order
In order to comply with these directives, a fishing port manager needs to have a good understanding of both the natural environment existing around the fishing harbour as well as the environment generated within the harbour's infrastructure. Since water is the underlying link which connects the various fishing activities together, (such as netting, storing and icing onboard, handling inside a harbour and eventual sale to consumers) and since most water supplies originate outside the harbour area, the fishery harbour manager must ensure that water entering the harbour is chemically and biologically fit for human consumption. Unfortunately, this task is rendered more difficult in countries with a strong indigenous cottage industry, which, through the indiscriminate use of highly toxic chemicals (chemical dyes, pesticides, paints and solvents), generally leads to problems associated with groundwater pollution
The major contaminants of concern, in potable water supplies are
a) Suspended solids)
b) Biodegradable organics (proteins, carbohydrates and fats)
c) Pathogens)
d) Nutrients (Nitrogen, phosphorus and carbon)
e) Priority pollutants (highly toxic chemicals)
f) Refractory organics (pesticides, phenols, surfactants)
g) Heavy metals)
h) Dissolved inorganics (nuisance chemicals)
1.3 Suspended solids
The presence of suspended solids in water gives rise to turbidity. Suspended solids may consist of clay, silt, airborne particulates, colloidal organic particles, plankton and other microscopic organisms. The presence of particulate matter in water, whether organic, inorganic or due to higher micro-organisms, can protect bacteria and viruses from the action of disinfectants. The adsorptive capacity of some suspended particulates can lead to entrapment of undesirable inorganic and organic compounds present in the water and in this way, turbidity can bear an indirect relationship to the health aspects of water quality
Airborne particulate matter is of particular concern to facilities located near mineral stockpiles (coal, iron ore, bauxite, etc.) or down wind from large power stations (fly ash), timber saw mills (saw dust) or cement factories (cement dust). Rain water collection systems are particularly sensitive to such airborne particulates because they usually augment local potable water systems and act as conduits for pollutants to enter potable water systems. Large quantities of aromatic hydrocarbons are also generated by the combustion of fossil fuel in oil-fired power stations and industrial kilns
1.4 Biodegradable organics
Composed principally of proteins, carbohydrates, and fats, biodegradable organics are measured most commonly in terms of BOD (Biological Oxygen Demand). BOD is the quantity of oxygen required for the oxidation of organic matter by bacterial action in the presence of oxygen. The higher the demand for oxygen (the more organic the pollution) the less is the oxygen left to support life. Urban sewage commonly has a BOD of 500 mg/litre. Harbour basin water should have a BOD in the range of 50 to 150 mg/litre
1.5 Pathogens
The major contaminants of concern, in potable water supplies are
a) Suspended solids)
b) Biodegradable organics (proteins, carbohydrates and fats)
c) Pathogens)
d) Nutrients (Nitrogen, phosphorus and carbon)
e) Priority pollutants (highly toxic chemicals)
f) Refractory organics (pesticides, phenols, surfactants)
g) Heavy metals)
h) Dissolved inorganics (nuisance chemicals)
1.3 Suspended solids
The presence of suspended solids in water gives rise to turbidity. Suspended solids may consist of clay, silt, airborne particulates, colloidal organic particles, plankton and other microscopic organisms. The presence of particulate matter in water, whether organic, inorganic or due to higher micro-organisms, can protect bacteria and viruses from the action of disinfectants. The adsorptive capacity of some suspended particulates can lead to entrapment of undesirable inorganic and organic compounds present in the water and in this way, turbidity can bear an indirect relationship to the health aspects of water quality
Airborne particulate matter is of particular concern to facilities located near mineral stockpiles (coal, iron ore, bauxite, etc.) or down wind from large power stations (fly ash), timber saw mills (saw dust) or cement factories (cement dust). Rain water collection systems are particularly sensitive to such airborne particulates because they usually augment local potable water systems and act as conduits for pollutants to enter potable water systems. Large quantities of aromatic hydrocarbons are also generated by the combustion of fossil fuel in oil-fired power stations and industrial kilns
1.4 Biodegradable organics
Composed principally of proteins, carbohydrates, and fats, biodegradable organics are measured most commonly in terms of BOD (Biological Oxygen Demand). BOD is the quantity of oxygen required for the oxidation of organic matter by bacterial action in the presence of oxygen. The higher the demand for oxygen (the more organic the pollution) the less is the oxygen left to support life. Urban sewage commonly has a BOD of 500 mg/litre. Harbour basin water should have a BOD in the range of 50 to 150 mg/litre
1.5 Pathogens
The most common and widespread danger associated with drinking water is contamination, either directly or indirectly, by sewage, by other wastes, or by human or animal excrement. If such contamination is recent, and if among the contributors there are carriers of communicable enteric diseases, some of the living causal agents may be present. The drinking of water so contaminated or its use in the preparation of certain foods may result in further cases of infection. Natural and treated waters vary in microbiological quality. Ideally, drinking water should not contain any microorganisms known to be pathogenic to man. In practice, this means that it should not be possible to demonstrate the presence of any coliform organism in any sample of 100 ml
Pathogenic organisms found in contaminated water may be discharged by human beings who are infected with disease or who are carriers of a particular disease. The principal categories of pathogenic organisms are, as shown in Table 1.1, bacteria, viruses, protozoa and helminths
1.5.1 Bacteria
Faecal pollution of drinking water may introduce a variety of intestinal pathogens - bacterial, viral, and parasitic - their presence being related to microbial diseases and carriers present at that moment in the community. Intestinal bacterial pathogens are widely distributed throughout the world. Those known to have occurred in contaminated drinking water include strains of Salmonella, Shigella, enterotoxigenic Escherichia coli, Vibrio cholerae, Yersinia enterocolitica, and Campylobacter fetus. These organisms may cause diseases that vary in severity from mild gastro-enteritis to severe and sometimes fatal dysentery, cholera, or typhoid
The modes of transmission of bacterial pathogens include ingestion of contaminated water and food. The significance of the water route in the spread of intestinal bacterial infections varies considerably, both with the disease and with local circumstances. Among the various waterborne pathogens, there exists a wide range of minimum infectious dose levels necessary to cause a human infection. With Salmonella typhi, ingestion of relatively few organisms can cause disease; with Shigella flexneri, several hundred cells may be needed, whereas many millions of cells of Salmonella serotypes are usually required to cause gastroenteritis. Similarly, with toxigenic organisms such as enteropathogenic E. coli and V. cholerae as many as 108 organisms may be necessary to cause illness. The size of the infective dose also varies in different persons with age, nutritional status, and general health at the time of exposure
Table 1-1: LIST OF INFECTIOUS AGENTS POTENTIALLY PRESENT IN DRINKING WATER CONTAMINATED BY SEWAGE
ORGANISM | DISEASE | REMARKS |
Bacteria |