WATER TREATMENT at the Calco Chemical Division V . L K I N G , C. H. B E A N , A N D R. E. LESTER, Calco Chemical Division, American Cyanamid Co., Bound Brook, N . J., AND W I L L E M RUDOLFS, New Jersey Agricultural Experiment Station, New Brunswick, N. J.
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ΠΓ^ΗΒ Caico Chemical Division, employing about 4,500 people, produces pri marily dyestuffs, intermediates, rubber chemicals, pharmaceuticals, and mineral acids (H 2 S0«, HC1, HNO«). I n the manu facture of dyestuffs, pharmaceuticals, and related organic chemical materials, i t is
necessary to have clean, neutral water, whether an the form of steam, water, or ice, f o r the production of materials of uniform qmality. It is necessary t h a t the water be relatively free of calcium and magnesium salts ancl, in some cases, iron and alumi n u m salfes which would form lakes if pre cipitated in the dyestuffs and dull the colors, interfere with their solubility, and lower their dyeing power proportionally to t h e amotont of lake formed. The necessity for "water treatment in manufacturing is apparent). The present centralized sys t e m of water treatment w a s started early in 1930,. prior to which the treatments wereloe=ated a t different places scattered through the plant. A large percentage of t h e steam gener a t e d is nised in the processes, requiring a high per-centage of boiler water make-up, running 90 per cent on t h e average t o as high as 95 per cent at times. Since fil tered, so>ftened water is used for make-up, it is neeessary to give this water supple mental treatment to prevent scaling, em-
brittlement, and corrosion in t h e boilers and carry-over i n the steam. T h e several cooling ponds which supply cooling and condensing water to individual processes must be treated also to pre vent oxygen corrosion of t h e equipment, growths of slimes, and deposits of mud and scale in t h e coolers, and growths of algae in t h e ponds. Slimes especially are good insulators and interfere seriously with heat exchange unless kept under control. The growth of algae in t h e coagulation ponds must be kept in check so t h a t t h e treated water m a y have good color or absence of color. Air-conditioning equipment of the water-spray type must b e treated from time to time t o prevent growths of bac teria and fungi which give rise t o odors if allowed t o persist. Certain time-tried methods of water treatment cannot b e used, or cannot be used in their full effectiveness because of lack of tolerance for certain chemicals, such as copper, iron, chlorine, in the water used in t h e production of rubber chemi cals, aniline, and 0-naphthol. T o circum vent difficulties and, at t h e same time, to be able to make satisfactory water, a variety of treatment processes is neces sary. N o potable water is treated.
Cooling Water T h e plant uses 20,000,000 gallons of water daily from the Raritan River, more in summer according to t h e need for cool ing water. All of this water i s screened through a 0.375-inch mesh traveling screen to remove leaves and other floating or suspended debris. T o improve this operation further, 0.25-inch mesh screens of greater height and with higher pressure cleaning sprays applied o n the downside will be installed as soon as the equipment can be obtained. Most of these 20,000,000 gallons of water are used for cooling, get no treat ment other than screening, and are used directly from the pipe line. The Caico plant does a considerable amount o f re frigeration, and a part of the water used for cooling in the refrigeration process is discharged to t h e effluent. Another part of the cooling water is run to t h e coagula tion ponds and makes u p a substantial
River pumping station
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portion of the 3,000,000 gallons used daily as treated water. In winter, this quantity will run 850,000 gallons per day, and it is expected that during the summer the en tire requirement for treated water may be supplied by the cooling water. Coagula tion is usuaEy very good in this warm water, but algae grow freely in it, and the alkalinity is increased through loss of CO2. More treatment is required, therefore, than when the cooler water, direct from the river, is used. The treatment plant consists essentially of pumping stations, chemical dosing equipment, coagulation, settling, filtration, softening, and chlorination, and special treatment for specific purposes. The pipe line from the river pumps to the coagulation ponds runs under the powerhouse where the coagulants are added in proportion to Sow, together with acid or caustic soda for adjusting the pH values, when necessary. This method of treatment is undergoing changes, because of the additional water anticipated from refrigeration. A new chemical-treatment house has been built at the ponds adjacent to the drain line which carries the waste refrigeration water to the ponds. This affords a more convenient and more accurate means of administering the chemical treatment. There are two main ponds—3,000,000 and 3,500,000 gallons capacity. They are used alternately, so that there is always one pond full of wellcoagulated and adjusted water ready for filtering and softening. These ponds also provide water for fire protection. The Raritan River water has nominally a hardness of 60 p. p. m. (3.5 grains per gallon) mostly bicarbonate, with about 60 p. p. m. total alkalinity, and a pH of 7.0 to 7.5. However, alkaline waste water discharged into the river above the plant raises the pH of the water more or less depending upon dilution at high or low flows, and increases the hardness because of the calcium hydroxide alkalinity. The river water is affected almost entirely by the amount of water in the river, because the rate of production of the calcium hydroxide does not change. This results at times in only 30 p. p. m. hardness and a pH of 6.6 (during periods of heavy surface run-off) to 140 p. p. m. hardness and a pH of 9.5 (during periods of extreme drought).
Coagulation and settling ponds with pump house in center
use of sodium aluminate is not necessary and is undesirable because it raises the alkalinity of the water. When the river is turbid, sodium aluminate is used at all times and sometimes double doses of alum and sodium aluminate are required when the river is very muddy. Flocculation is effected during passage of the water through 700 feet of pipe to the ponds and during the flow through the ponds. It is most important that coagulation be com plete so that no alumina is left in solution to interfere with manufacturing processes or boiler operation. From April to November, sodium hypo chlorite is used directly at the ponds to kill algae; 1.25 p. p. m. available chlorine during daylight is usually sufficient to keep the algae in cbeck without leaving a chlorine residual in the water, or, a t most, from 0.01 to O.02 p . p. na.; occasionally a dosage of 2.0 p. p. m. is required- Chlo rine residuals are undesirable because they may interfere with some processes. Cop per sulfate cannot be used because of the plant tolerance of O.05 p. p. m. of copper. The coagulated water is returned to the powerhouse where it is filtered through standard pressure sand filters which are backwashed daily to keep them clean. Bacterial growths develop in the filters at times and flakes of mud and dead algae adhere t o the sand. It has been the practice to boil out the filters once a year with caustic soda to refresh the beds. This is done usually in the fall or early
M e t h o d of Treatment
In treatment, first aluminum sulfate is added (34 p. p. m. during normal times of clear water in the river), then 3.4 p. p. m. real sodium aluminate. The pH of the water is then adjusted t o 7.2, or as close to it as possible, with the use of caustic soda or sulfuric acid. The amounts used are calculated from frequent analyses. As much as 900 pounds per day of caustic soda has been used at one time and up to 1,000 pounds per day of concentrated sulfuric acid at another. Ordinarily, the adjustment requires much less material. When the river water is very alkaline, the V O L U M E
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winter when the accumulations become heaviest. The boiling out is accom plished by the addition of 100 pounds of dry caustic soda to a bed 8 X 12 feet, allowing an approximate strength of 0.4 per cent sodium hydroxide. Steam is applied to a maximum temperature (to keep the "sand boiling") for a period of 8 hours. The impurities, mostly organic, are destroyed, leaving very clean sand. Specification of Finished W a t e r
After filtering, the water is passed through greensand softeners working upflow on the sodium cycle and softened to a maximum of 8.5 p. p. m. hardness, which is satisfactory for plant use. The finished water must meet the following specifica tions: 1. Appearance. Clear, water-white. 2. Color. Not over δ color units (Hellige color disk). 3. Turbidity. Not over 5 p. p. m. S1O2 by Hellige turbidimeter. 4. Suspended Matter. None. 5. Iron (Fe). Not over 0.5 p. p. m. 6. Hardness (calcium and magnesium). Not over 8.5 p. p. m. as Ca0O3. 7. Aluminum (Al). Not over 0.2 p. p. m. 8. pH (cold). 7.0 to 7.3. 9. Copper (Cu). Not over 0.05 p. p. m. Daily laboratory control analyses are made to cover all requirements and the softeners and pH of the treated water are under constant supervision and control. Hourly samples of the softened water are 1047
taken and t n e rates of flow of the softeners checked hourly s o that the best operating conditions may be maintained. Addi tional tests made when required are: 10. 11. 12. 13. 14.
Total solids. N o t over 150 p. p. m. Hydroxide (OH). None. Carbonate (C0 3 ). None. Bicarbonate (HC0 3 ). N o t over 8 5 p. p. m. Chlorides (NaCl). N o t over 26 p. p. m. Control o f p H
"usually the water produced is well within these specifications. The Raritan River is a "flashy" stream, however, and sometimes during and after heavy rains, it takes some weather prophecy in order to anticipate changes i n dosage in time to assure the desired result. Again, on hot, dry days, t h e pH of t h e river water may rise from 7.5 in t h e morning to S.5 in the late afternoon. This calls for careful manipulation of acid feed during the day so that the pH 7.2 point for optimum co agulation c a n be maintained within reason. A t night, t h e acid is shut off, except during extremes of drought when the alkaline condition carries on through the night independently of the d a y pH rise which is the result of growth of algae. T h e treated water is stored in elevated tanks and distributed t o the plant through steel pipes lined with a bitumen material and through Transite lines. The bitumen lining has occasionally given some trouble by melting off and clogging smaller lines, especially when t h e water becomes heated, but it is very effective i n keeping down the iron pick-up of the treated water. Boiler water is treated with trisodium phosphate fed directly and continuously into the boiler drums to precipitate the residual hardness of 8.5 p. p. m. in the treated water. T h e phosphate is fed into the drums to prevent carrying over of salts into t h e superheaters. The amount used i s regulated b y biovvdown analysis for P 0 4 in solution which is maintained at 30 to 50 p. p. m. Sodium sulfite is used to remove traces of oxygen still left in the feed water after going through the deaerating heater and is fed into the closed reservoir after t h e heater. This is regu lated also b y blowdown analysis which should show 30 t o 50 p. p. m. Na 2 S0 3 . After treatment, the boiler feed water must pass t h e following specifications:
pound boilers and to 1T 500 p. p . m . in the 900-pound boiler. Attention to ρ Η and deaeration help prevenst the c=arrying over of dissolved salts, an«*d the boilers are equipped with steam w^-aslicrs as a further protection against carrji-r-ovei*. T h e river water cooEitains 10 p . p. m . silica, and even thougfcÉi thore= is n o proof that silica is added Thy t h e greensand softeners because the "s-trealedi water also contains 10 p. p. m., thaerc ne^ver h a s been trouble from silica denposits in t h e 480pound boilers, althougMh the iboiler water may show as high as 2CD0 p. p>_ m. silica a t times. The blowdownt* pli r-uns 10.8 t o 11.3, and there h a s bee=n suirweient caustic alkalinity t o keep silica - from d e p o s i t i n g i n the boilers. Since the tsurbine=s run mostly noncondensing, there Oiave fc>een no deposits in them. I t is o>ossibl*e that silica will give trouble i n openrating :a 90O-pound pressure boiler. One oof the wheels in a condensing turbocomppressor showed a dust on the blading irsi whie^h silica was identified. Although IMO attejcnpt i s made
a t present t o remove silica, it may be necessary t o do so. Flake ice is produced from, treated wa*fcer. The calcium chloride refrigeration brines are kept adjusted to p H 7.5 to 8.0. S o dium dichromate is used to maintain a c o n centration of 0.2 gram per 100 c c . to inhibit oxygen corrosion. Cooling Ponds Cooling ponds demand more attention than formerly. With the war effort demanding higher 'production of some m a terials, efficiencies must be kept a s high, as possible, with a minimum o f time lost in making repairs. In addition, there is difficulty in getting new condenser tubes and other equipment. The cooling ponds cannot be treated uniformly because they serve different operations, the demands or conditions of which vary. The light o i l shop spray pond uses sodium dichromate held at about 150 p . p. m. for prevention o f oxygen corrosion. Intermittent chlorination w i t h
p H . Cold, after feed water heater, 7.8 t o 8.2. Dissolved oxygen. After the heater and after addition of Na^SOa, none. T h e blow-down samples should show no hardness. Sulfate-soda ratios are 3:1 and over on either the 480-pound or 900-pound boilers; the treated water is always regulated so that additional sulfate to the feed water is not necessary. There is no evidence of trouble from emforittlement. Boiler bLowdown is held t o a maximum of 2,500 ρ. ρ. na. total solids in the 4S01048
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t u b e s for adequate protection against corrosion. Another pond gives no trouble from a l g a e or slime, but it is difficult t o control t h e pH of the water because this pond has a tendency t o go acid. The p H is adjusted o n each 8-hour shift t o 7.5 or above. Sodium dichromate is used here successfully in concentration of 150 p. p. m. for prevention o f corrosion. Three spiral oleum coolers gave trouble from mud deposits until the water velocity through t h e m w a s speeded up sufficiently to prod u c e scouring action. This, with the chemical treatment, has apparently ended t h e trouble. Xhe aniline shop, which has one tower p o n d and t w o spray ponds connected in series, has a make-up of three times its capacity. Production has outstripped the normal growth of the plant and fresh water is needed to hold down the temperature because of lack of sufficient cooling capacity. T h e strain o n this system was relieved s o m e w h a t b y running treated water for
sodium hypochlorite, after which a.qua ammonia i s added, is practiced t o prevent the g r o w t h of a very tough alga. Ttuee p. p. m. of chlorine a r e necessary to g e t a good kill. This treatment automatically destroys t h e bacteria and fixngi i n the condensers. This shop h a s developed the use of compressed air injected, into the unbaffled condensers, while still filled with water, to clean o u t m u d deposits. U s e of compressed air i n baffled aerators is n o t so effective. The v i o l e n t agitation removes practically all o f the deposits, a n d is particularly effective after chlorination. The air i s introduced i n t o the vertical condensers at a pressure o f 125 pounds. The air i s fed into t h e 18-inch b y 15-foot condensers b y means o f a 0.375-inch inlet, w h i c h results in a jarring action. Cleaning i s repeated each 8-hour shift. The pond pH i s kept at 7.5 or above. Phosp h a t e treatment was tried i n this pond, but was unsuccessful because of excessive algae growth and because i t was impossible to deposit a uniform phosphate film o n the
boiler make-up through an admiralty metal condenser, whereby some heat was captured. Phosphate treatment and sodium dichromate were tried, but could not b e held at concentrations t o a degree that would prevent corrosion troubles. Meanwhile, it w a s found that a sulfite brine produced in the plant as a by-product had t h e property of combining with dissolved oxygen almost immediately at temperatures a s low a s 40 ° F. This may be due to small quantities of organic materials which a c t a s catalyzers. Ordinarily sodium sulfite combines with dissolved oxygen quickly only a t higher temperatures. This brine is used continuously as an antioxidant, enough of it being used to maintain a n excess of 20 p. p. m. Na^SOs a t the hot well. This treatment, with pH adjustment to 7.5 or over, has resulted in comparative freedom from corrosion of the cooling surfaces. However, slimes still gave trouble until it was found that maintaining 0.5 p. p. m. copper sulfate in the water discouraged their growth. Microscopic examination showed many bacteria, some of which could be identified, fungi, and a few diatoms which were believed to be skeletons. T h e removal of this slime has resulted in a satisfactory increase in the thermal efficiency of the condensers and i n a reduction in corrosion on account of the difference in potential between areas insulated with slime adjacent t o clean areas. Sodium fluoride has been used as an algioide and more use might b e made of it if it were easier to obtain. Relatively large doses are necessary for good results, but i t has proved successful where chlorine is not desirable because of the danger of leaving undesirable residuals. More extensive use is desirable in water-spraycooled air-conditioning equipment, for example, instead of sodium hypochlorite which is now used when the equipment becomes fouled. Well water is used in the air conditioners because it is cooler than river water in summer, but one of the wells became contaminated from surface drainage and it was necessary to use treatment. A simple by-pass feeder was hooked up to the water inlet line and sodium hypochlorite fed slowly at night until a faint odor of chlorine was detected at the air outlet. This procedure, repeated weekly, kept the conditioners clean. All of these treatments are under rigid control. The powerhouse laboratory does all of the routine analysis for treated water and boiler feed water, whereas the effluent plant laboratory takes care of the cooling ponds and all special work. The methods of analysis are standard. Before a method is adopted, it is worked out in detail by the standards laboratory and passed by it before being put into practice. Failures from lack of analysis or inaccurate analysis are almost nonexistent. PRESENTED before the Division of Water, Sewage, and Sanitation Chemistry, at the Detroit Meeting
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