the treatment of some chemical industry wastes

The Treatment of Some Chemical Industry WastesAuthor(s): Thomas PowersSource: Sewage Works Journal, Vol. 17, No. 2 (Mar., 1945), pp. 330-337Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25030013 .

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THE TREATMENT OF SOME CHEMICAL INDUSTRY WASTES *

By Thomas Powers

The Dow Chemical Company, Midland, Michigan

The Midland Plant of the Dow Chemical Company is one of the

largest chemical plants in the country within one enclosure. Here the

manufacture of over 400 products requires the use of some 250 million

gallons of water per day which discharge to the Tittabawassee River

having a minimum flow of 150 c.f .s. Pollutants in this river discharged from oil fields, municipalities, and industries are borne to the Saginaw

River and thence to Saginaw Bay and Lake Huron (Figure 1). There

Figure 1.?Usage of Tittabawassee and Saginaw Rivers below The Dow Chemical Company plant at Midland, Michigan.

are many users of these receiving waters. The first use is agricul tural for a 20-mile frontage. The city of Saginaw and many of its in

dustries have the Saginaw River as a water source and also use it for

wastes disposal. Almost the entire length of the Saginaw River be

tween Saginaw and Bay City could be classed as recreational frontage *

Presented at Seventeenth Annual Meeting, F.S.W.A., Pittsburgh, Pa., October 13, 1944.

330



Vol. 17, No. 2 TREATMENT OF CHEMICAL INDUSTRY WASTES 331

while the watercourse itself is open to lake boat commerce. Many of the industries in Bay City also use the river as a water source and for

wastes disposal. The city of Bay City has its water source in Saginaw Bay some 4 miles from the mouth of the river. Saginaw Bay is a pro ductive commercial fishing water and has miles of recreational frontage.

Waste waters from the Dow Midland plant requiring treatment total 75 m.g.d. Strong waste brines are stored in some 400 acres of ponds and released during periods of high flow by arrangement with down stream water users. The general plant wastes of 50 m.g.d. flow through some 40 acres of sedimentation ponds. Strong phenolic wastes require a 30-acre storage pond prior to treatment. A 50-acre pond is used to

treat and cool a difficult waste resulting from the direct quench of cracked oil gases.

General Plant Wastes

The general plant wastes of 50 m.g.d. which are now settled in 40

acres of ponds before discharge to the river have a B.O.D. population

equivalent of about 130,000. The wastes result from the manufacture

of all products other than the phenolic type. The oxygen demand is created by such compounds as polysulfide, sulfites, alcohols, and many

aliphatic combinations.

A treatment plant for these combined wastes is being studied. Ex

perimentally it was found that activated sludge would do a creditable job of oxidizing this waste.

Specific Chemical Wastes

Too often investigators fail to evaluate the oxygen demand of cer

tain chemical wastes. Polysulfide wastes resulting from the manufac ture of a synthetic rubber and also from the treatment of cyanides have an immediate oxygen demand. Polysulfide rapidly oxidizes to thiosul f ate as shown :

2Na2Sx + 302 = 2Na2S203 + (x)S J With the proper bacteria present the oxidation is completed :

2Na2S203 + 02 = 2Na2S04 +2S j 2S + 302 + 2H20 = 2H2S04 + (282 calories)

These reactions should proceed in a two stage process since the oxida tion of sulfur and thiosulfate results in an acid water which would re

lease H2S from the polysulfide if added, and the excess alkali contained in polysulfides would slow up the oxidation rates. It is believed that few activated sludge plants would be capable of receiving much poly sulfide waste without seriously affecting the effluent because of the high oxygen demand.

The use of blowing-out towers has proved effective in removing certain, low boiling organics such as styrene, ethyl benzene, chlorobenzol, alcohols and benzene.



332 SEWAGE WORKS JOURNAL March, 1945

Complete elimination of certain waste waters such as cracking

process quench water has proved necessary. The oxidation of organic matter, using bacteria as catalysts, is by

far the cheapest method available. If an industry under severe pollu tion restrictions has gone as far as practical with biological treatment,

what more can be done?

The oxidation of residual taste and odor pollutants can be accom

plished chemically using chlorine, bromine or perhaps ozone. The

control of oxidation by chlorine or bromine (Figure 2) must be exact or there is great clanger of increasing the taste and odor.

Figure 2.?Oxidation of 0.20 p.p.m. phenol in water by chlorine and bromine.

The adsorption of residual organics by activated carbon might also become feasible provided the biological or extraction process is

carried to its practical limits. The treatment of phenolic wastes has been the subject of many

articles for the past twenty years. As Mohlman (1) pointed out years ago a pound of phenol requires 2.38 pounds of oxygen when completely oxidized to C02 and H20 :

C6H5OH + 702 6C02 + 3H20

94 J224 1 ::2.38




Eldridge (2) concluded that inhibition of biological oxidation does not start until about 180 p.p.m. of phenol are present.

The cresols, aniline, salicylic acid and most of the lower substituted

phenols are readily oxidized biologically. Within their range of solu

bility, the toxicity of phenolic compounds to bacteria (3) increases with the molecular weight (Figure 3). The fact that most of the higher substituted phenols are insoluble in acid solution should lead toward pretreatment of such wastes by acidification.

Figure 3.?The distribution of phenolic compounds with respect to their molecular weight and

phenol coefficient.

Phenolic Waste Treatment

The units for treatment of the phenolic wastes of the Dow Chemical Company are (Figure 4) : strong waste storage pond, Dorr clarifier, four trickling filters, and an activated sludge plant and 50 acres of effluent ponds.

Strong phenolic wastes are pumped to the storage pond by all bronze

open-impeller centrifugal pumps and Saran discharge lines. The pond is a treatment unit which serves to equalize flows and waste concentra

tions besides precipitating substituted phenols which are insoluble in acid solution. The volume of strong waste averages about 1.25 m.g.d.

with a concentration of phenolics of about 600 p.p.m. The pH might vary between 2 and 4 and contain an acidity of 270 parts per million as HC1. Storage capacity of 42 million gallons permits control of feed to treatment process.




Phbnouic WAS-re HTnecATM&N-r Pi_a>k Thk Dow Cmkmicau Company

1944

Figure 4.?Layout of phenolic waste treatment plant of The Dow Chemical Company at Mid

land, Michigan.

Weak waste flows of 12 m.g.d. in the winter and 20 m.g.d. in the summer contain from 5 to 1 p.p.m. of phenol. This waste is mixed with

the strong wastes (and filter effluent recycle when necessary) and is

pumped to the clarifier at a rate of 15 m.g.d. The clarifier at this plant serves to skim light oils and settle whatever heavy oils and precipitates are present. No phenol is removed in this unit (Figure 5).

It is possible to pump the mixed waste to the strong waste pond

Figure 5.?Trickling filters and sedimentation unit treating phenolic wastes.




when weak waste concentration of acid, caustic or phenolics might create overloaded or toxic conditions. The underflow from the Dorr

clarifier is lagooned in a portion of the strong waste pond. Overflow

from the clarifier flows by gravity to the four trickling filters which are 142 feet in diameter on top with the 21/i>-3%-inch blast furnace slag

media forming the outside wall on a 45 degree slope, which makes the

bottom diameters 162 feet. The center gallery and complete bottom

coverage of "?rmere" tile were designed to give maximum aeration

(Figure 6). Motor driven, two-arm distributors are of ten-inch pipe

Figure 6.?Effluent gallery of trickling filters shown in Figure 5.

with eight-inch for the last ten feet. Water head on these units is sufficient to rotate them so that the motor serves as a speed regulator

most of the time. The temperature of the mixed waste leaving these

filters varies from 53 deg. F. to 95 deg. F. The pH of the mixed liquor is

kept above 6.1 and below 8.0. The phenol concentration for normal

feeds varies between 30-50 p.p.m. Concentrations higher than that are

recirculated. The beds average 9.75 feet deep and obtain removals of

phenol from 4.29 lbs. per 1000 cu. ft. at 56 deg. F. to 9.0 lbs per 1,000 cu.

ft. at 83 deg. F. with a feed rate of 10.2 m.g.a.d. Removal of B.O.D.

varies from 15.8 lbs. per 1,000 cu. ft, to 27 lbs. per 1,000 cu. ft. at the

respective temperatures given.




The population equivalent of the B.O.D. load to this plant is about

125,000.

Activated Sludge Plant

The activated sludge plant (Figure 7) receives the filter effluent and excess weak wastes through a grit chamber. Return sludge is mixed

with inflow at the effluent end of the grit chamber and the flow is directed to each of the 5 batteries. Three mechanical aerators in series

in a 24-foot by 75-foot tank with a 15-foot depth, followed by a 24-foot

width, 70-foot length and 10-foot depth settling tank, comprises one

battery.

Figure 7.?Activated sludge plant treating phenolic wastes at Midland plant of The Dow Chemical Company.

Return sludge is delivered by slip pipes to a channel leading to screw pumps which lift the sludge to the channel set on top of the

wall between No. 2 and No. 3 batteries.

The activated sludge plant has been found to be capable of oxidizing

1,300 lbs. per day of phenol or 3,300 lbs. per day of B.O.D.

The overall removal effected by various units is illustrated (Table

1). The final effluent to the river averages less than 0.4 p.p.m. of

phenol. The Dow Chemical Company has proceeded on the basis of

eliminating or recovering wastes wherever possible and providing

biological treatment where feasible. Each chemical plant must be




Table 1.?Summary of Phenolic Waste Disposal?The Dow Chemical Company Midland, Michigan

Removal of Phenol by Various Units

Pounds of Phenol per Day

Total Received

5152 5745 4775 4332 5703 3987 4063 4040 3999 3892 4054 4496 5463 4444 4028 4499

Removed by Filters

3880 4853 3875 3184 4547 3217 2947 2695 2746 2603 2655 3089 4805 3996 2651 3715

Removed by Activated

810 515 346 523 914 590

1011 1316 1188 1193 1280 1234 540 334 294 561

Removed by Ponds

172 139 153 299 136 73 55 55 32 60 80

117 61 43 41

105

studied separately and every waste evaluated with respect to its

pollutant characteristics.

References

1. F. W. Mohlman, "Biochemical Oxidation of Phenolic Wastes/' American Journal of Public

Health, 19, 145 (1929). 2. E. F. Eldridge, "The Biological Filtration of the Phenolic Wastes from a Oas Plant/*

Mich. Eng. Exp. Station, Bulletin No. 87, November, 1939, pp. 1-10.

3. C. M. Suter, "Relationships Between the Structures and Bacteriacidal Properties of Phe

nol,' '

Chemical Reviews, 28, 269 (1941).



the treatment of some chemical industry wastes

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