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. McGregor. 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 fronts. Our guest Professor Brooks has spent the last 10 years of his career with the concern for some of these problems and has contributed 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. 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 that water pollution problem around Southern California in the Los Angeles or San Diego area are really not exist. 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 polluted environment way take 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 they assume 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 if a city is near the coast like Los Angeles or San Diego the ocean is the very easiest place to get a

well in the 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 in 85 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 to in fact step to my 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. But of course to study the water quality ocean also involves chemists and biologists and operation of sewage treatment plants of all sanitary engineers structural engineers are involved in building a facility. So really there are others who doubt Amasis is

just one phase. However I think it's in this particular phase of food dynamics that we've done some interesting things in the last 10 to 15 years. All right. Just mention these things are 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 diffuser holes 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 a very serious menace to public health. This doesn't occur in the really nice States anymore but it does occur in some of the underdeveloped countries where there are epidemics of cholera typhoid other serious diseases caused by my work. But in the United States the level of pollution is mostly at the level of depletion of oxygen damage to fish like the aesthetic nuisances odors increasing Turby. Buddy I'm this kind of pollution is completely absent in Los Angeles right lowest level pollution is perhaps associated with subtle changes in the ocean and ocean life just the way there are subtle changes of the land when man moves into. So jack rabbits 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 overall the effects are very minimal compared with what they would be if we took wastes 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 your notion front. And this community is very much concerned with the problem of disposing of their waste and would. Wish to dump them as you might say into the ocean. How might they approach the problem what are some of the considerations some of the questions that arise. Well be an engineer and designing a system has to consider really three phases the collection of all these wastes liquid waste from the houses apartments the industries building a system of sewage for the collection conveying them to a central place for treatment and then the third phase is

dispersal of the waste out into the environment. Now often in one city you have only the river for dispersing the liquids back but along the coast we use the ocean. So in that 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. So. 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 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 said the Titian 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 was 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 or an ocean. But then submarine construction was to learn the pipes or became submarine out follow the highway for ice all out that way. But now we have another step submarine out with multiple port diffusers for example it might be interesting to note that. The new out of 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 it'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 might such a piping arm be about

two and a half miles long. I see in the city of Los Angeles has one and so five miles long so it really goes a considerable distance and they way to ways out from the beach before they begin to show the whole don't start until you get to nearly 8000 feet short of fact it's already a hundred and sixty five feet deep at the very far and 193 deep effect when the effluent comes out of these holes which are only say an average of three inches in diameter three times to rise in a plume very much like smoke plume in the atmosphere except you can't see it under the ocean. I'm curious to know if the fluid comes out and is 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 we called Smoke plumes or sewage effluent plumes. Now the mixing is far better in the ocean. And in fact during a very long time in the summer. Particularly the effluent forms a cloud which stays well below the ocean surface. What on earth would cause it to stay submerged. But it 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's only 50 degrees Fahrenheit because of this change in temperature the water near the. Bottom of the cold water is 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 it 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 why 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 heavy bottom water. In fact up to maybe 100 or 200 parts of this heavier water her each part of the sewage treated sewage effluent. Now when you mix when you mix the fresh Roya discharge all that heavy bottom water it produces a mixture which simply can't make it to the surface it finds a level of neutral buoyancy applied way up. And so it remains suspended so to speak right affecting what like our smog. Yes it's very active. The trick which the atmosphere plays on us to make a smog hanging in the ground is a very same trick we're using in the ocean to protect ourselves from. Just 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 a cove a colder bottom layers to trap these. Contaminants and they and we live by a warmer upper layer and were completely free from these contaminants. So on the surface we are 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 is another difference I should say the most of the waste a goes into the ocean is a natural organic material which is easily decomposed in the by the ocean life plankton and so on whereas one of the problems of the air pollution is reporting in large quantities of unsaturated hydrocarbons which are not a natural constituent of the

atmosphere and do not decompose. It is easy way. Well in mentioning the constituents of fluent into the ocean you didn't mention anything about bacteria. Is this a problem in itself. Well our only. Constituents in the sewage effluent probably bacteria at the most critical one because with a large dilution which we get in the ocean several hundred parts to 1 0 of the other requirements like dissolved oxygen are very easily taken care of but the bacteria. Must either die in the ocean or if there is not sufficient die off in the ocean they must be taken

care of by carnation and the sewage treatment plant. You know I should really emphasize that. The disposal of sewage in the ocean is really a joint. Joined with treatment plan and land. For example in Los Angeles are two very large treatment plants. This is processing before it right approximately a story to the right. 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 that is necessary to do this for example. Oh the grease is removed and solids 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 major devices by 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. Oh how large a capacity. And 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 to fix system which takes care of about 3.7 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 is does this NG include also the storm drain and drain control. Well you might be interested to know that the sewage system or the sanitary of waste are simply too small to handle a storm water as I mentioned earlier. Do you see this flow through which corresponds only three hundred seven inches of water spread over the Los Angeles area which drains in other words if you try to take three hundreds of inch of rainfall and put it into the sewer you would have into the sanitary sewer you had just as much water as we have for the sewage in the houses even though it does amount to about 100 gallons per capita. Rainwater has to enormously riders so it rains several inches in a day around

here when we must have a far bigger system for 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 a storm water in the cemetery sewage mixes. And then the volume of this flow 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. Is it possible to handle these. The treatment of such problems in the laboratory are they are an experimental methods in a laboratory or theoretical methods that one can use if they have been doing some interesting work in a laboratory a Kel-Tec concerned with these clowns in which slight density differences

is a big problem associated with the plume. Right that's right now we have reproduced. Conditions similar to the ocean where you have a plume discharge where we produce in a small tank actually have these temperature gradients or variations that you have in the laboratory tank so we make a gradation of the salt content we we work with maybe six feet long four feet wide a couple feet deep in this tank with successively with layers of slightly decreasing salt and taking off today. Thank you don't they to fill these tanks but then you get a sort of sandwich effect layer after layer of water decreasing density so that simulates the effect of it. That's right and then we can observe behavior and the surprising thing is that we could also make quite a good analysis of the rhetoric going to calculate

which checks now in the laboratory observation but also checks the ocean for example we can actually predict when. Come to the surface and when it will stay submerged for example in San Diego 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. Then we also observe this is true in the ocean as well. Is this dispersion a process that goes on when the plumes come out from the UP fall thorough enough so that a person out in that area swimming about or boating about would notice and hear these discharge during the

summer time when the cloud is submerged below the surface. The layman would have the greatest difficulty finding any evidence whatsoever. We need some good scientific equipment and yes he is in fact the only time they become aware of it. When they see the pipe being constructed then the pipes are buried in the can but the president literally can't detach from their normal senses. It would take very sensitive instruments to see anything that's normally the case. Los Angeles and San Diego. I'm curious you mentioned that we destroyed some 600 million gallons a day I presume that as the population increases this number will continue to increase. And will we reach some sort of saturation point. Where I think we're at the point now where wastewater reclamation will become a growing activity in Los Angeles. 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 wastewater can be reclaimed a reasonable cost and quite reasonably recharge groundwater and subsequent fact it's cheaper and you're suggesting then that the. For the flu and not necessarily continuing increase with time as the population grows here and the domino I think but probably stay about the same and the growth will be pro should be I think in the wastewater. But actually even if you have a reclamation plan if you still have the waste products from the reclamation plant so you still have to get these out to the ultimate disposal more concentrated but certainly of a more limited amounts of that right so we don't necessarily look forward to the time when the fluid is constantly increasing. I think pretty good shape for the future. Well I'm certainly very much encouraged by these remarks. Certainly the

water district 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 of our 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 the end of Cal Tech's Jet Propulsion Laboratory and his guest Dr. Norman Brooks professor of civil engineering. Joining us again for our next program when another subject of interest to scientist and layman will be discussed. 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

this station by a national educational radio. They say is the national educational radio network.