Some of the methods of controlling marine pollution are as follows:
Maintaining dredging, that is, dredging required to maintain a particular depth, adds sediment to the water column and would not be needed if there were no sediment supply to shoal up major channel areas.
This type of dredging has been not a one shot affair, but it has been almost always necessary to periodically redredge the accumulated sediment from these channels and harbor areas. This continual sedimentation has been a normal process which occurs whether man is present or not.
In some instances the activities of man tend to accelerate the sedimentation process but this has been not necessarily always true. For example, coastal plain estuaries, often the result of river basin flooding, tend to be a rather ephemeral event in geological time.
They get formed when water level rises, and they disappear with the continual process of deposition of material eroded from the higher reaches of the watershed. Another example of natural erosion has been found on the west coast of the United States in the western most portion of California (that portion where more than 90% of the population lives).
This area was formed by erosion of the Rocky Mountains and deposition of the eroded material at the base of the mountains.
The most obvious solution to the problem of maintenance dredging has been to cut off the sediment supply to the areas where sedimentation has been a major problem. This can be carried out in a number of different ways.
The most effective of all has been to prevent upstream erosion, but at the same time this is perhaps the most difficult. The entire watershed must be policed very carefully to make sure that the natural landscape gets changed to such an extent that erosion no longer takes place.
This implies extensive terracing and replanting of areas that have been denuded for one reason or another. Of course, this also implies that extreme measures must be taken in areas that do not have natural cover, such as agricultural areas or areas where construction is underway. A certain amount of this is being done.
Another method of preventing sediment form reaching the undesired are to provide settling ponds. The water is released after it has dropped the major portion of its load and is allowed to proceed downstream.
The major disadvantage of this system has been that it is essentially a temporary solution since the ponds will fill up rather rapidly, needing either building of new ponds or dredging of some sort.
Sometimes the sedimentation that takes place in a channel area is a result of sediment loads that are introduced into the marine environment from nearby rather than those carried from far up-stream.
This takes place, for example, when a channel gets dredged with unstable sides so that the material just tends to slough into the deeper regions. This needs continual dredging as the removed sediment has been almost immediately replaced by bottom material from the sides.
One method of correcting this situation is by stabilization of the bottom. Adding larger, denser material such as gravel to the bottom has been a technique utilized occasionally, although this has been usually more expensive than dredging so that it has been not done too often.
Bottom stabilization, however, is a technique that is being used more and more to prevent the movement of bottom materials within relatively small contiguous areas.
Another possibility for preventing the accumulation of sediments in undesirable areas has been to change the natural circulation patterns so that sediments get deposited in an area where they do no damage.
This may be carried out in various ways: by changing the physical dimensions of estuarine areas, by putting dams in selected areas, and even by changing the circulation pattern by planting grasses to increase bottom friction.
Another method to be considered in decreasing the amount of suspended sediments has been that involved in controlling the numbers and types or water craft allowed in particular areas.
In regions that have been relatively shallow and narrow, high speed vessels tend in churn up the bottom, putting sediments back into the water column that had previously settled out.
In addition, large wakes are generally produced that tend to erode the sides of the waterway by the mechanical action of these relatively high energy waves breaking on the shoreline. Both these effects can get decreased by the simple expedient of limiting the speed of boats in certain areas.
It has been a fairly effective method; however, if the traffic is extremely heavy it may be necessary to limit the total number of vessels, in addition to their speed.
In addition to the general clarity aspect of pollution caused by dredging, there has also been a toxic one. Sediment retrieved from harbour bottoms has been especially likely to contain a relatively high concentration of industrial pollutants such as oil and heavy metals.
During the dredging operation there has been a likelihood of some of this material’s finding its way back into the water column, but of more concern has been the longtime leaching from dredge spoil dumping areas.
Various methods, such as diking and the construction of artificial islands are utilized to minimize this leaching but their performance under all conditions has been not too well known. Further research in the handling of dredge spoil gets needed at this time.
2. Oil Pollution:
Another problem that, to a certain extent, appears amenable to prevention at the source is that involving oil. Unfortunately, the sources of oil in the marine environment have been extremely difficult to delineate.
All the experts agree that the greatest terrestrial source of petroleum products in the ocean is used crankcase oil. Some go so far as to indicate that this source supplies more petroleum to the sea than any other source.
This may be true because within the last decade or so the habits of American motorists are changed markedly to the extent that a large portion of them now change their own oil, discarding the used oil in a manner that probably makes it to end up in storm sewers.
The major reason for this probably is, the almost complete disappearance of the used lubricating oil re-refining industry in recent years since it was not economically feasible to re-refine oil. However, with the modern continual increase in the price of new oil, the re-refining industry has been having a rebirth so that a large portion of the oil previously thrown away will now be reused.
Another entirely different source of oil in the marine environment has been that resulting from accidents that take place during shipping and transferring processes.
Generally speaking, the more handling steps involved, the more accidents and associated losses can get expected. The figures as to how much has been actually lost in handling accidents compared to that lost in normal ship procedures, such that as pumping bilges, has been not well known, but there has been no doubt that a very large portion of the oil reaching the marine environment has been the result of poor handling procedures in both the operation of vessels and the transfer of oil from one carrier to another.
Better procedures are required, but perhaps even more than better procedures, stricter enforcement of accepted safe procedures would go a long way to decreasing the amount of oil that enters the ocean each year.
When a tanker empties its load of oil, the dynamic characteristics of this vessel get markedly changed. Its weight gets decreased about a thousand times and therefore it becomes extremely difficult to drive the ship, because it was designed to be driven with a full load.
Therefore, when most tankers do not have a load of oil, they will fill their tanks with water for ballast. When they return for a fresh cargo of oil, they must pump this water from the tanks, releasing large amounts of oil as the residue left in the tanks gets washed out.
There are many schemes which are suggested for decreasing the amount of oil that is wasted in the ballasting-unballasting process; however, it is not clear at this time how effective these processes have been or how effectively any requirements can be enforced.
Modern supertankers have been extremely large vessels and therefore have major structural weaknesses, so that occasionally they will break up in unusually heavy seas. They have been simply not designed to be utilized under unusual storm conditions, so that there will continue to be losses of this type in rough weather.
In passing, it should be mentioned that once oil gets spilled at sea under large wave conditions (usually) the case when accidents occur, there has been no way for this oil to be retrieved.
On the other hand, oil may be retrieved in harbor areas where the sea surface is relatively calm, but only when there are waves no higher than approximately 1 meter.
The obvious way the only way—to prevent oil from getting to the marine environment when a ship founders has been to prevent the accident from occurring in the first place.
Alternatively, once the accident has taken place the oil must be prevented from escaping from the ship. It has been somewhat doubtful whether these solutions will ever be possible.
3. Industrial Pollutants:
Most industries are using large amounts of water for cooling purposes or as an integral part of the manufacturing process.
Consequently, industrial effluents may be having waste products, heat, leached material from heat exchangers, or even incidental house-cleaning wastes. If the industry, for example, has been using water as a coolant, the heat exchangers must constantly be cleaned to keep the heat exchange efficiency high.
These cleaners may be more toxic than process wastes. Consequently, it has been extremely desirable to treat all industrial effluents.
Some industries have tried to modify the entire process rather than just clean up the effluent. This often causes an increase in efficiency with a lower overall production cost. If this expenditure cab be recouped in a relatively short period of time.
This obviously might be expected to be a very cost-effective method of handling unwanted effluents. However, in many cases, there has been no increase in operating efficiency, with the net result being an increase in manufacturing costs passed on to the consumer.
Society must then make a decision as to how much it has been willing to pay for a particular product visa vis the amount of pollution introduced in the manufacture of this product.
4. Antifouling Paint:
Sometimes pollution comes from the use of antifouling paint on boats. During the summer time in temperate waters the growth rate of marine organisms get increased markedly, especially those organisms setting on fixed surfaces.
An untreated boat hull left in the water for a period of just a few weeks will need enough growth to cut the available speed for a given power input by fifty per cent. Consequently, all owners of boats left in the water have been very careful to apply some coating to the underside to prevent the accumulation of marine organisms.
For large cargo ships or tankers, this could make savings of thousands of dollars in fuel costs. Common practice has been to paint the bottom of the boat with antifouling paint.
Antifouling paint has been so used to leach a toxic material into the water in just the proper amounts so that all organisms setting on the hull will get killed.
However, the older types of antifouling paints, those that use copper as a toxin, released enough material to the environment not only to kill possible fouling organisms but also to be harmful to other marine creatures at some distance from the boat. Thus, there has been a movement of to improve the quality of antifouling paints by drastically reducing this leaching to toxic material into the water.
The solution that has been to use new paint vehicles in conjunction with new toxic materials so that the toxic material has been almost completely retained within the vehicle, requiring organisms to come within the very short distance of the boat to be affected.
One result of recent research is to develop a family of paints using acrylic resins as vehicles and tribunal tin fluoride (TBTF) as the primary antifouling ingredient. In the first few years of use this paint holds great promise because it is less toxic in the water, lasts longer, and does not allow bottom growth more effectively.
In their very effectiveness these new paints pose a problem, because the toxin gets retained within the paint for a longer period of time. Paint scrapings have been now more toxic than they were with the old copper bottom paint.
This means that it has been somewhat more dangerous to strip the paint from the bottom of the boat when applying a new coat and precautions must be used to prevent the old paint from getting back into the water environment.
When sandblasting large ships, for example, precautions have to be taken to retain the sandblasted material rather than allowing it to be simply washed away. Thus, the solution of one problem presents another, but these problems have been solvable if some care has been taken to see that additional health hazards do not get created.
5. Pesticide and Herbicide Pollution:
Some of the juicer pollution scandals that have taken place in recent years have involved various pesticides and the problem has been that many of the chemical compounds get introduced for public sale before the total effects of these materials have been known.
It seems to be almost an insurmountable problem to determine what the total effects of a new compound will be before it has been put on the market because so many new products are introduced every year.
However, a large portion of the problem has been undoubtedly due to basic carelessness. In both the manufacturing and use of these materials proper precautions are not being into consideration. Many users, for example, undoubtedly believe that if a certain amount per unit area will suffice, twice as much will produce twice as much control of either weeds or bugs.
This excess toxin is washed into the streams and ends up killing marine organisms rather than protecting plants. It would be evident that more effective control of both the manufacture and use of pesticides and herbicides would go a long way toward eliminating undesirable side effects.
6. Solid Waste Pollution:
The disposal of solid waste has been very necessary and there even seems to be a fear that if the solid water problem is not solved, eventually there will be no room left for people. Because of this fear, large amounts of solid waste get dumped in the ocean.
Some of these solid wastes take the form of sludge from sewage treatment plants whereas other consists of large pieces of discarded consumer products. In the latter case the problem might very well solve itself as the cost of scrap metal continues to increase.
One possible use for sewage treatment sludge has been in refurnishing land disfigured by strip mining. Often the overburden removed to get at the coal seam has been not capable of supporting life nor has it been even particularly stable.
The addition of sludge from sewage treatment plants is considered as a method of soil treatment to make it possible to support a viable plant population. It is a concept that has not been tired yet but one which will be tried when it becomes economically feasible to transport the sludge to the strip mine.
Another possibility for using the sewage sludge, if it contains only nutrient materials, has been suggested and has been considered by some of the Middle Eastern oil producing countries. The idea has been that empty tankers be filled with sewage sludge for the return voyage rather than with ballast water.
This sludge will then be utilized to bring the desert regions back to a point where they have been capable of supporting a large agricultural industry.
Other forms of solid waste being dumped in near shore areas have been dumped there primarily because there has been no other acceptable depository. One method of decreasing the severity of this problem has been simply to decrease the amount of solid waste produced by society.
Packaging of consumer items, for example, seems to be a good place to start. Form a disposal point of view the catsup bottle is probably the worst possible package. The package weighs more and takes up more space than the contents.
The Navy has done excellent work in definite limitations aboard ship, but not too much has been done with the private sector of society simply because there hasn’t been enough action on the part of consumers to insist upon small volume and weight packages.
One possible exception to this has been the introduction of light weight plastic bottles for large size drinks to replace the heavyweight glass variety. They are somewhat thinner than glass, weigh less, and may be incinerated, so the disposal problem has been somewhat alleviated. However, with the continuous increase in petroleum costs, plastics might not remain economically feasible in the future.
7. Recycling and Reclamation:
It has been found that biological communities living in the sea need a certain amount of physical shelter. Some species just like to be alone, whereas in other cases the young of the species require places to hide to protect against predation.
A marsh or wetlands area has been a good breeding place because both of these conditions prevail. It is found that in many cases these conditions can be created artificially by introducing large junk articles such as old automobiles or worn out ships to form effective artificial fishing reefs.
There has been a disadvantage to using waste products for this sort of activity. One has been that in many cases these junk, objects get transported to undesirable areas by dynamic oceanic forces. Pollution has been not controlled when automobile fenders and doors wash up on swimming beaches.
When creating a finishing reef, steps must be taken to retain the integrity of these reefs for a long period of time. If proper attention has been paid to the magnitude and nature of oceanic forces, artificial reefs might be made relatively permanent.
With the present state of the economy where things are somewhat more expensive, it appears that more items will find themselves in the near future on the list, of materials to be recycled or reclaimed.
Industrial processes will alter as it becomes more feasible to extract materials from the waste stream from a cost standpoint and, at the same time industrial. Waste streams will become less and less polluted.
Even in the area of multiple waste product use, like the combination of waste heat from either manufacturing or electrical power generation and waste nutrients from sewage treatment plants for the purposes of aquaculture, cost will always be the controlling factor.
It is known that elevated temperatures arid the artificial addition of nutrients will increase growth rates of many organisms markedly.
The choice of which organism to grow has been involved not only with which would be best to grow, but also which there has been a market for setting up an aquaculture system involves picking organisms which respond favourably to the environment, developing a system by which the optimum growth rate can get produced, developing a marketing system so that the end product will be sold at the maximum possible price and assuring the continuing existence of a market for everything produced.
Not only has been science included but also sociology and economics must be considered, and it is probably in these latter two areas that the major difficulties reside. Hence, no sophisticated aquaculture systems employing both waste heat and nutrients have been developed at this point, but it has been probably only a matter of time before we will have extensive aquaculture using man’s waste products.