About science; About ocean pollution

This is about science produced by the California Institute of Technology and originally broadcast by station KPCC in Pasadena California. The programs are made available to this station by national educational radio. This program is about ocean pollution meeting to discuss this subject. Dr. Robert McGregor Leean of Cal Tech's Jet Propulsion Laboratory and his guest Dr. Norman Brookes professor of civil engineering. Here now is Dr. McGrath am. We've been hearing more and more in recent years about the problems of the pollution of our atmosphere and of the natural waterways. This evening in our conversation we will discuss one aspect of this general problem namely the control of pollution of our ocean front. Our guest Professor Brooks has spent the last 10 years of his career with the concern for some of these problems and has contributed in an important way to the various county and city offices in Los Angeles with solutions to these problems. I'm curious to know

Norman how you as a civil engineer first became interested in this particular area. Well actually it was back in the days when I was a graduate student. There was a problem to improve the mechanisms of ocean disposal. And there was a study needed in a fluid mechanical sense to figure out how to better disperse these wastes into the ocean. We have come quite a way I think in the last 10 years so that now I think the problems of water pollution in Los Angeles are in much better shape than air pollution. In fact we might say tonight we're talking about the how we control the pollution because I think the water pollution problem around Southern California in Los Angeles or San Diego area are really not exist. Now in my remarks a moment ago I joined together the notion of atmospheric pollution and water pollution.

I wonder is there really a similarity in these problems in any way. Yes there is a similarity because the air and water are both fluids in fact. A man who lives in a vast fluid environment. We take the air and water from our surroundings and use them often adding contaminants and then they must develop ways to put them back into the environment without causing us harm. In fact a civil engineer is responsible for controlling many of these withdrawals and returns to the environment. You mentioned a moment ago that many of these wastes are dumped into the ocean. Why the ocean in particular. Well the city is near the coast like Los Angeles or San Diego. The ocean is the very easiest place to get a helmet dispersion of the liquid water

waste. After all the amount of water available in the ocean for dilution is ever so much greater than what's available at any of our natural streams. In fact the Los Angeles River has no water tolerated during most of the year. And as we know this. So then the essential point is that we use the ocean in order to dilute and spread the waste materials Terran facts up to about a level. In fact the control of the ocean pollution depends on people in many disciplines. My particular interest is in how to get this material widely dispersed back into the ocean so there will be no pollution. Better course to study the water quality ocean also involves chemists and biologists and the operation of sewage treatment plants of all Senator engineers structural engineers are involved in the building of facilities. So really we're a rather fluid dynamics this is just one phase of it. However I think it's in this particular phase

of fluid dynamics that we've done some interesting things in the last 10 to 15 years. I might just mention these things there one is the fact that we can now control the mixing of these sewage effluence into the ocean so it's no longer just a dumping operation we can design pipes with diffuser homes and so on so that we can control where this effluent goes where these. Plumes are generated and we can relate all of this to the oceanography along the coast to get a very good result. I'm curious to know when you talk about water pollution. What particular constituents or ingredients are you talking about. Well you can think of water pollution as at several different levels. First of all you might have such bad pollution that you would have very serious menace to public

health. This doesn't occur any really and United States anymore but it does occur and some of the underdeveloped countries where there are epidemics of cholera or typhoid or other serious diseases caused by by water but in the United States our level of pollution is mostly at the level of depletion of oxygen damage to fish life aesthetic nuisances odors increasing tourbillon. But even this kind of pollution is is completely absent in Los Angeles right lowest level pollution is perhaps that did it with subtle changes in the ocean or ocean life. Just the way there are subtle changes in the land when man moves into so the jackrabbits don't run in the same places they used to and so perhaps the different fishes in the ocean don't swim in entirely the same places but over only the effects are very minimal compared with

what they would be if we took her waist and simply dumped them out of the ocean without any engineering control. I'm curious to know if you consider as an academic exercise here an enlightened community living near an ocean front and this community is very much concerned with the problem of disposing of their waste and wood. Wish to dump them as you might say into the ocean. How might they approach a problem what are some of the considerations some of the questions that arise. Well they an engineer designing a system has to consider really three phases the collection of all these ways good ways from the houses apartments the industries building a system of sewers but it's a collection conveying them to a central place for treatment. And then the third phase is dispersal of the waste out into the environment. Now if you're in one city you have to only the river for dispersing the liquids back

but along the coast we use the ocean. So when I case we don't have to provide as much treatment because much of the final treatment of the organic material is done in the natural environment of the ocean itself. And I get the impression from your comments that this whole business of waste disposal into the ocean is not a simple idea such as taking a pipe and sticking out on the beach and letting it go so to speak. Yes people get the idea perhaps that I don't realize how much engineering study goes into it for example. Justin last December in 1065 the county sanitation district of Los Angeles completed a new ocean outfall pipe going 12000 feet out into the ocean. What do you mean by far. Well it out from has a funny name it used to be used in I guess for pipes which just let the water waste water fall

out into a river an ocean but then the submarine construction was learning the pipes or became submarine out follow the highways for I thought about it that way but now we have another step submarine outfalls with multiple port diffusers for example you might be interesting to note that. The new route for the County Sanitation District has seven hundred forty two small holes through which the treated sewage effluent is jetted into the ocean. This is just a single pipe that goes out into the ocean. It's one big pipe that's 10 feet in diameter but the last four thousand four hundred feet of it have these holes in the side of the pipe. How long how long my touch of piping on. Oh it would be about doing 1/2 miles long. I think many of our centers has wanted So five miles long so it really goes a considerable distance.

And would they wait a ways out from the beach before they begin to show that yes these homes don't start until you get to nearly 8000 feet of shore in fact it's already a hundred and sixty five feet deep at the very far end of the outfall pipe it's 190 feet deep respect to me. The effluent comes out of these holes which are only saying they have reached three inches in diameter. He tends to rise in a plume very much like a smoke plume and he and you have a sphere Except you can't see it under under the ocean. I'm curious to know if the influence comes out in this plume like form doesn't it just rise to the surface and spread about the ocean back to the beach perhaps. Well it's a very very interesting problem of Oceanography

here because in the old days we used to run these pipes out and dump the effluent out the end of the open pipe and it did rise up to the surface mixing some as it came but it did contaminate the ocean surface but no when you make 700 of these little so-called smoke plumes are different plumes. Now the mixing is far better in the ocean. And in fact during a very long time in the summer particularly wavy effluent forms a cloud which stays well below the ocean surface. What on earth would cause it to stay submerged read other works. It works something like this. In the summer the ocean temperature at the surface is about say 68 degrees. But down to 200 feet depth it so only 50 degrees Fahrenheit

because of its change in temperature the water near the. Bottom of the cold water is a slightly heavier per cubic foot say of water than the surface water for example. The water at the bottom might be two point six percent heavier than fresh water but the water at the surface of the ocean might be only 2.4 or 2.5 percent heavier than fresh water. No there is a slight difference in the how heavy this ocean water is this gives me the impression that there would be a point for us then. Well that's right the sewage effluent is essentially like fresh water and it starts to rise. But as it jets from the. Near the bottom of the ocean it mixes. It sucks in great quantities of the surrounding cold

heavy bottom water. In fact up to maybe 100 or 200 parts of this heavier water for each part of the sewage treated sewage effluent. Now when you mix when you mix the fresh Royer discharge with all that heavy bottom water it produces a mixture which a simply can't make it to the surface it finds a level of neutral buoyancy applied way up and so it remains suspended sort of speak right affecting what like our smog. And yes it's very active. The trick which the atmosphere plays on us to make a smog layer hanging in the ground is the very same trick we're using in the ocean to protect ourselves from. To some extent from contamination it works like this in the atmosphere. We have very warm layers above us here so the cold cooler air

near the ground can't mix vertically and escape. And in the ocean we use the colder colder bottom layers to trap these contaminants and they and we live by the warmer upper layer and were completely free from these contaminants. So on the surface we were trapped along with our waste products and the atmosphere within this ocean and with the water front we can just dump our waste and let it be trapped in that large sink so to speak. Well there's another difference I should say the most of the waste a goes into the ocean is a natural organic material which is usually decomposed in the by the ocean life the plankton and so on whereas one of the problems of the air pollution is reporting in large quantities of these unsaturated hydrocarbons which are not a natural constituent of the atmosphere and do not decompose.

In the end it is easy way. Well in mentioning the constituents of the fluent into the ocean you didn't mention anything about bacteria. Is this a problem in itself. Well of all the constituents in the sewage effluent probably bacteria is the most critical one because they were the large dilutions which we get here in the ocean. I mean several hundred parts to 1 0 of the other requirements like rabbits on target for holders and dissolved oxygen very easily taken care of but the bacteria. Must either die in the ocean or if there is not sufficient die off the ocean they must be taken care of by carnation and the sewage treatment plant.

You know I should really emphasize that the disposal sewage in the ocean is really a joint joined with the treatment plant on land. For example in Los Angeles are two very large treatment plants. This is processing the foreign rights rights of the story to the right city. We study the ocean to see what the capacity of the ocean is for assimilating the waste and then we give the required treatment. On land it is necessary to do this for example. OA grease is removed and solids and and so on. Just the way in the atmosphere the release of stack gases has to be perceived very often by control.

I could perceive better devices but also you can't you can't just throw out everything but on the other hand you don't have to adopt the attitude that you can only put drinking water back into the ocean so there's a balance here between the man made the man control treatment and the natural treatment of the environment allergic capacity. There's our sewage system handle in the Los Angeles area. But I think if you take the two two systems together in Los Angeles the county it is sitting on is a County Sanitation District system which takes care of about three point seven million people in the city of Los Angeles a system which serves about three million people. Together they produce about over 600 million gallons of sewage per day. Probably these are some of the largest unified systems for ocean sewage disposal anywhere in the world.

You talk about the sewage system. Norm this is does this NG include also the storm drain and drain control. Well Tom you're right. Be interested to know that the sewage system for the senator it wastes are simply too small to handle the storm water as I mentioned earlier to you if it be this flow of sewage corresponds only 370 inch of water spread over the the Los Angeles area which drains in other words if you try to take three hundreds of an inch of rainfall and put it into the sewer you would have into the sanitary sewer you have just as much water as we have for the sewage in the houses even though it does amount to about 100 gallons per capita amount of rainwater is used to enormously larger so it rains several inches in a day around here when we must have a far bigger

system for a storm. So there are literally two separate issues two separate systems to drain to the ocean but you know in the East many of our large cities like New York have combined sewers so that they. When it does rain the storm water and the and this and this cemetery sewage mixes and then the volume of this floor becomes so large that they have to overflow and bypass the treatment plant so this is one of the most difficult problems of pollution control today. Many systems do not have a separation. But is it possible to handle these. The treatment of such problems in the laboratory are they are an experimental method in a laboratory or theoretical methods that one can use. Yes we have been doing some interesting work in the laboratory Kel-Tec concerned with these four pounds of which light density differences this is the main problems associated with the plume. Right that's right

now we have reproduced. Conditions similar to the ocean where you have a plume discharge will reproduce in a small tank. You don't actually have these temperature gradients or variations that you have. And yes in the laboratory tanks we make a gradation of the salt content we we work with tank maybe six feet long four feet wide and a couple feet deep and we fill his tank with successively with layers of slightly decreasing salt and take all day. Thank you don't they fill these tanks but then you get a sort of a sandwich effect with a layer after layer of water slightly decreasing your density so that simulates the effect of the time wasted That's right and we can discharge the buoyant plumes and observe their behavior and the surprising thing is that we can also make a quite a good analysis and thorough rhetoric on

our counter least which which checks now in the laboratory observation but also checks the ocean observation for example we can actually predict when the. Clue more come to the surface and when it will stay submerged for example but at San Diego it we find it only takes two degrees temperature difference from the top to the 200 foot depth to keep the cloud below the surface all the time winter and summer and the analysis says this and then we also observe this is true in the ocean as well. There is this dispersion process that goes on when the plumes come out from the OP for their own up so that a person out in that area swimming about or boating about would notice and hear these discharge.

Well during the summertime when the cloud is submerged below the surface the layman would have the greatest difficulty finding any evidence whatsoever. You mean from good scientific equipment to yes there is in fact the only time they become aware of it all is. When they see the pipes being constructed then the pipes are buried and nobody can. But the public literally can't detect from their normal senses and we take very sensitive instruments to see money that's normally the case. Los Angeles and San Diego. I'm curious you mentioned that we discharge some 600 million gallons a day I presume that as the population increases this number will continue to increase and will be reached some sort of a saturation point. Well I think we're at the point now where wastewater reclamation will become a growing activity the Los Angeles area. You know you might say it doesn't make sense to keep putting this freshwater into the ocean at the same time we're trying

to bring more water from great distances here and the wastewater can be reclaimed. Reasonable cost and quite feasibly for recharging the groundwater and subsequent reuse in fact it's cheaper than you're suggesting then that. For all the fluent we're not necessarily continuing increase with time as the population grows here and IMHO I think there but probably stay about the same and the growth will be pro should be I think in the wastewater. You know but actually even if you have a reclamation plant you still have the waste products from the reclamation plants and you still have to get these out to the ocean out for ultimate disposal. More concentrated but certainly of more limited amounts of that right so we don't necessarily look forward to the time when this fluid is constantly increasing. I think we're really in pretty good shape for the future. Well I'm certainly very much encouraged by these remarks and certainly the what

it does takes to county and city offices have made a considerable amount of progress toward solving some of the problems of controlling the ocean pollution. The similarity to the problem of the atmospheric pollution is certainly to be no doubt to be reassured when you go to the beach next summer they know how much engineers have been concerned with developing these works for you. Well I appreciate very much this opportunity to talk about this Norman and thank you again. Well thank you. This was about science with host Dr. Robert McGregor of Cal Tech's Jet Propulsion Laboratory and his guest Dr. Norman Brooks professor of civil engineering. You're invited to join us for our next program when two more prominent scientists will discuss a topic of interest about science is produced by the California Institute of Technology and is originally broadcast by station KPCC in Pasadena California. The programs are

made available to the station by national educational radio. This is the national educational radio network.