Industrial Process Water (6) Christenson, G. W.,et al., Ibid., 43, 1509-19 (1951). (7) Corey, R. C., et aE., “Experimental Study of Effects of Tangential Orifice of Air,” Air Pollution Control Association, Baltimore, Md., May 26, 1952. (8) Falck, L.,et al., “Savannah River Plant Stack Gas Dispersion and Micro-Climate Survey,” Atomic Energy Commission, AEC DP-19 (June 1953). (9) Friedlander, S. K.,et al., “Handbook on Air Cleaning,” Atomic Energy Commission, 1952. (10) Hatch, L. P., American-Scientist, 41, 410-21 (July 1953). (11) Humphrey, P. A., “Meteorological Program a t National Reactor Testing Station,” Sanitary Engineering Conference, Chicago, September 1952. (12) McCullough, G. E., IND.ENG.CHEM.,43, 1505-9 (1951). (13) Ranz, W. E., and Johnstone, H. F., “Some Aspects of the Physical Behavior of Atmosphere Aerosols,” Proc. 2nd Natl. Air Pollution Symposium, p. 35, Pasadena, Calif., May 5-6, 1952.
(14) Smith, W.J., “Iron-Combustible and Chemical Resistant -411’ Filters for High and Low Temperature Use,” Minutes of Air Cleaning Seminar, A.E.C., Ames, Iowa, September 1952, in press. (15) Stanford Research Institute, “The Industrial Utilization of Fission Products, a Prospectus for RIanagement,” R4arch 1951. (16) Theis, C. V., “Work of the Geological Survey in Connection with Sanitary Engineering Problems of the A.E.C.,” Atomic Energy Commission, 129. (17) Thomas, H.A,, et al., J. Am. Water Works Assoc., 46, No. 6, 562-8 (1953). (18) Urban, Walter, Food Eng. (February & March 1953). (19) White, Fred, “The Weather Bureau and the Atomic Energy Commission,” Atomic Energy Commission, September 1952. RECEIVED for review March 14, 1953.
ACCEPTEDAugust 29, 1953.
Waste Disposal. in the Los Angeles Area T w o factors have had material influence on policies controlling industrial waste disposal in the sewerage systems of the metropolitan area of Los Angeles County: the wide range of chemical wastes acceptable for ocean disposal but not for disposal to ground waters or fresh water supplies and the short supply of acceptable water demanding integrated conservation and re-use of industrial process waters. The flexibility of the two major sewerage networks and availability of ocean disposal have permitted the unprecedented industrial expansion of the area to be met without serious difficulty.
A. M. RAWN County Sanitation Districts of Los Angeles County, Los Angeles, Calif.
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N THE Los Angeles area industrial wastes may be broadly classified in two categories: liquids containing little or no settleable solids, which may be disposed of through sewers to final treatment and disposal, and solid or semisolid wastes to be discharged a t sea or a t legally licensed land disposal sites. The two classifications overlap somewhat, in that a number of industrial wastes may, with pretreatment, be discharged in part into the sewerage system but in their pretreatment there is generated a solid waste which falls into the second classification. SEWERAGE AGENCIES
U
The Los Angeles metropolitan area is served by two principal sewerage agencies: The first is the city of Los Angeles, under whose control is the system which serves the major portion of that city, the major portion of the city of Vernon, and the cities of Burbank, Glendale, Beverly Hills, Culver City, Santa Monica, and San Fernando. This vast city system serves an area of more than 500 square miles containing a population of nearly 2,500,000 as well as the major portion of the industries which make Los Angeles and its metropolitan area third in manufacturers in the nation. There are two termini to the city’s system, the larger near E l Segundo discharging to Santa Monica Bay, where the city has constructed a high-rate activated sludge plant with a capacity of about 250,000,000 gallons per day and an ocean outfall extended seaward some 4000 feet. The second is a small primary plant December 1953
on Terminal Island, Wilmington, with a capacity approximating 10,000,000gallons per day and 1000-foot outfall into the harbor. The present flow to the plant at El Segundo is about 240,000,000 and that to the Terminal Island plant about 8,000,000 gallons per day. The second main system in the area is provided and administered jointly by 11 County Sanitation Districts. It serves an area of a little over 500 square miles and a population in excess of 2,000,000. Thirty-five of the 45 incorporated cities in Los Angeles County are served in whole or in part by the districts’ system, as are large tracts of unincorporated but densely populated areas. A part of the industrial activity of the metropolitan area almost equal t o that in Los Angeles city originates in the area served by the sanitation districts. The sanitation districts operate a single primary subsidence, separate sludge digestion plant near Lomita. The effluent from the plant flows through a tunnel under the Palos Verdes Hills and is discharged into the ocean 5000 feet off the south rocky shore a t a depth of 110 feet. Currently the plant and outfall facilities are being greatly expanded. Flow a t the districts’ plant approximates 160,000,000 gallons per day. These two large sewerage systems are of the separate type, in that they are used only to carry sanitary sewage and industrial wastes. The wisdom of this is perfectly apparent when one compares the average daily sewage flow from the area of about 400,000,000 gallons per day with the enormous storm flows that
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result from the torrential character of rain common to this area during the short rainy season. As sewerage systems are of the separate type and because of the vast area served by the sanitary sewers, every precaution is taken to conserve capacity. This is particularly true in Los Angeles County because of the phenomenal growth in population of this metropolitan area and its corresponding industrial expansion, factors which have rendered inadequate, from the capacity standpoint, many sewers built only a short time ago. As an example of this, the flow through the Sanitation Districts’ Joint Disposal Plant in 191.0 was about 20,000,000 gallons per day, while today, 13 years later, it is about 160,000,000 gallons per day. Building sewerage facilities, either in the Los Angeles city or districts’ system with capacity extending over a long future would impose such a great obligation upon the taxpayers a t the time they were built as t o render the procedure illogical, if not impossible; thus not only the capacity of the separate sewers is jealously guarded by those who operate the systems but the sewerage systems themselves are in an almost continuous state of expansion and enlargement. Mention was made of the extent of the systems. The sanitation districts own and operate nearly 500 miles of trunk sewers, the longest of which is 65 miles. The system of the city of Los hngeles is about the same degree of magnitude. Most of the water supply of this metropolitan area is secured from underground and the protection from pollution or contamination of these supplies is a primary public function. Regulations designed to protect underground waters are such as to protect such waters from pollution or contamination by industrial wastes, and complete compliance is demanded. This in turn imposes the additional burden upon the separate sewers of carrying nonputrescible but otherwise undesirable wastes, which under ordinary circumstances, or a t least circumstances under which the ground water was not so carefully guarded, would be discharged into natural drainage channels. Every application for industrial wastes discharges into the separate sewers is carefully scrutinized as to the possible undesirable content of the waste, its quantity, the possibility of rectifying it within the industry, its salvage values, re-use of water, and rendering the waste susceptible of discharge into storm drainage channels rather than the sanitary sewers. A further complicating factor which adds confusion to the industrial waste-disposal picture in this area is the tendency of sewage in the long, slow-flowing sewers to septicize and generate sulfides. At times, the addition of toxic salts in small amounts to sewage containing sulfides is beneficial. It also helps a t times to add strongly alkaline wastes in order to hold sulfides in solution, but the addition of acid has just the opposite effect and the discharge of comparatively large quantities of acid waste of moderate strength may result in the release of hydrogen sulfide gas to the extent that the life of the concrete sewer is materially shortened and entrance into the sewer becomes dangerous. The manifestation of this latter phenomenon was readily observable in a district sewer under repair, in the sewage of which insoluble sulfides were high and the semlage was fairly alkaline. A heavy shot of acid from a nearby plant producing sulfuric acid so changed the characteristics of the sewage that two men cleaning the sewer were killed by the released hydrogen sulfide gas. The many factors influencing the disposal of industrial wastes in the Los Angeles metropolitan area tend to intensify the examination to which every application for disposal of such wastes into the sewer is subjected. On the one hand, there are the compelling reasons of protection of underground waters and avoidance of public nuisance and health menace which urge the use of the separate seners for this purpose. On the other, the limited capacity of the separate sewers and trunks. treatment works, and pumping stations serving a growing population, increasing in a manner without precedent in history, influences the two large sewerage agencies to divert wastes away from the 2678
separate sewers wherever consistent and appropriate. An additional potent influence is the necessity for water conservation, and every new industry is carefully investigated for assurance that its water use is not in excess of reasonable requirements and that re-use, where possible, is planned. TYPES O F INDUSTRIAL WASTE
The wide diversity of manufacturing and industry in the Los Angeles metropolitan area gives rise to the generation of practically every conceivable type of industrial waste from ordinary cooling water to hospital and research laboratory discharges containing small quantities of radioactive isotopes. The careful scrutiny of applications for discharge of wastes produces some fine examples of industries’ cooperation in these perplexing problems. When the Lever Brothers plant was proposed for this area, the plant designer’s first estimate of industrial waste discharge was placed a t 20,000,000 gallons per day. In cooperation with the district and county engineers, the plans were changed and modified to include recirculation and flotation units to the extent that in the preliminary plans, the estimate of waste discharge was cut to 2,000,000 gallons per day. So thoroughly did the company’s engineers strive in the matter of conservation that the final design indicated a possible waste of 800,000 gallons per day, and with the plant in operation the measured waste is now 200,000. The process waters are recirculated until the organic content is too high for further re-use, while the amount of cooling water is restricted to that required for make-up. For years one of the greatest potential underground water pollutants was the oil well brine. Vast sums were spent on private collecting systems, pools, and pipelines to the sea or t o near tide waters, but the problem v a s never wholly solved until an agreement was reached between the oil operators in the sanitation districts’ area and the districts themselves. This agreement provided for allocation of definite capacity alloF5ances in the sewers to the oil operators within each district and the grouping of the oil operators in each of the major fields so that they could be dealt with through single representatives. Brines result from two general sources: the water that separates from the crude oil a t or near the well site, and its combination with refinery wastes in the cracking plants and elsewhere. Of the first of these two the districts’ system probably carries between 7,000,000 and 10,000,000gallons per day. These brines are cleaned up to 10 p.p.m. or less floatable oil by running through separating reservoirs and a t times through excelsior and other types of filters, No other type of treatment is given and the oil companies cooperate with the sanitation districts in limiting the hours during which the brines enter the sewers. The second of the two R-astes is more perplexing, containing sulfides, oils, and sulfonates. The sulfides are usually removed by a stripper, a tall packed column receiving the sulfide wastes, “sweet gas,” and steam. Oil removal is accomplished by a gravity oil separator, but the efRuent from such a separator still contains material quantities of emulsified oil. The districts do not find these particlilarly objectionable, provided the floatable oil is removed to the required minimum. The sulfonates arise from the treatment of cracked naphthas with sulfuric acid and subsequent neutralization of the extracted acids with sodium hydroxide, Considerable apprehension was felt about the possible effect of the sulfonates upon the precipitation and digestion process a t the districts’ plant, but a number of years of experience has indicated no ill effects and permanent connection permits have been issued to cracking plants where these wastes are generated. Oil wastes do not constitute a problem as yet in the Los hngeles city plant at E l Segundo. I n one of the smaller cities bordering the sanitation districts in the San GabrielValley Aerojet operates experimental firing aprons. Nitric and fuming nitric acids are used to oxidize organic fuels. Composition of the latter is, of course, strictly classified. The
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Industrial Process Water
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acid spillage and firing wastes are neutralized with marble chips to form a calcium nitrate salt. The Aerojet plant is actually tributary t o the small city’s sewage disposal plant, but the effluent from the city’s plant is returned to underground water basins and the Aerojet waste, being such as would contaminate the ground water, is run through a sewer of considerable length to reach the sanitation districts’ system for ocean disposal. It is probable that without the districts’ facilities close a t hand Aerojet would either have to cease operating or remove the neutralized wastes by tank truck to disposal in the sea. An example of beneficial industrial waste addition is afforded by the large chemical company in the industrial area south of the city of Los Angeles and tributary t o the districts’ system. This company was treating a copper-ammonium acetate maste for the separation of copper so that the waste could be safely disposed of in an open natural drainage channel. When sewers were extended to the company area, the treatment for separation of the copper was discontinued and t h e industrial sewage wasted into the sewer without further treatment because of its ability to convert soluble sulfides to the insoluble form and to inhibit further bacterial action. Actually the waste has been an asset to the districts in its control of sulfides. The W-hittier area waste-disposal company discharges supernatant liquor from a rotary mud sump to a district sewer. This waste, before treatment, has about 15 p.p.m. total sulfide, but these are effectively removed by the introduction of air at the suction side of a centrifugal pump, followed by short retention period under pressure and ultimate release in a gravity oil separator. The process was developed by a Pasadena engineer and the effluent from the waste-disposal area t o the districts’ system contains no dissolved sulfides and a floatable oil content of less than 10 p.p.m. One of the conditions precedent to the location of a large brewery in a n area underlain with valuable ground water aquifers was that the process waters be returned underground. To do this it was necessary to build a complete treatment plant to purjfy the brewery wastes to such a degree t h a t return t o the underground waters would not constitute a hazard. A sprinkling filter-oxidation, pond-percolation bed type of process was incorporated in refining the brewery wastes for reclamation. Domestic wastes were piped to the city’s collecting system. Only the water which enters into the beer and t h a t employed for domestic purposes is wasted. A classical example of the danger that exists in local treatment of unrestricted industrial wastes occurred at an activated sewage
sludge treatment plant serving four municipalities in the San Gabriel Valley. Upon one occasion there flowed undetected into the plant sufficient chlorinated hydrocarbons from a small plant manufacturing weed inhibitor to p u t out of use for a considerable period a number of water wells situated various distances downstream from the plant and taking water from aquifers into which the sewage treatment plant effluent flowed. This single occurrence, t o say nothing of others perhaps less serious but equally important, has convinced those whose business it is to prevent pollution and contamination of this area’s most valuable resource, that constant vigilance is the price of the area’s most valuable asset-water. Industrial wastes and how they are handled and regulated in this area could be described ad infinitum. An attempt has been made to select a few examples which are somewhat out of the ordinary and t o point up the problem with the restrictions and inhibitions that plague it. When toxic or aromatic solid wastes are removed by truck or otherwise, disposal sites are carefully chosen to prevent pollution of ground water. Industrial wastes disposal in this area will never be the simple, easily solved proposition t h a t it is in many other places. Although the completion or extension of the two bie; sewerage systems has greatly alleviated the problem’s perplexities, it is still no sinecure. The area is constantly expanding and the problems which now confront Los Angeles County are beginning to demand the attention of public administrators in Ventura, Orange, and San Diego Counties, where as time progresses the same care will have to be taken in the disposal of industrial wastes as is the case here. Finally, the difficulties spread beyond the areas in which the industrial wastes are generated. Southern California is justly proud of its beaches and other littoral waters. The state of California has an alert and conscientious Fish and Game Commission, ever watchful to prevent the destruction of shellfish and other aquatic life processes or spawning areas. And so, even though some wastes may flow through closed, lined, impermeable conduits from the source of their origin to the ocean, they must be regarded as dangerous until their composition and concentration have been rendered such as t o have no detrimental effect upon marine life. This compounds the problem, but it is being solved and the pattern set for Los Angeles County will probably serve as a useful tool in the development of neighboring but currently less populated areas. R ~ C E I V Efor D review April 10, 1953.
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December 1953
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INDUSTRIAL AND ENGINEERING CHEMISTRY
ACCFLPTED July 27, 1953.
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