I/EC A
W
INDUSTRIAL O
R
K
B
O
O
K
F
WASTES E
A
T
U
R
E
by W. B. Hart, Pantech, Inc.
A Case History of a Refinery Waste Wastes from a mid-continent refinery are treated in t w o stages—by flotation a n d by ponding to stimulate natural processes of purification
f \ MID-CONTINENT refinery is located
on the watershed of a stream which is a part of a river system to be cleaned up by the Pollution Abatement Authority of a mid-western state. T h e refinery could be classed as a "topping plant," but it produces certain specialties. The plant charge averages about 28,000 barrels per day of crude, from which it produces a high grade gasoline, fuel oils, some kerosine, asphalt, and coke. Its principal units are the crude distillation still, and cracking, polymerization, and coking units. Its principal products are a high grade leaded gasoline, some kerosine, fuel and furnace oil, and coke. Prior to the demand by the state that an unusually high degree of treatment be accorded the wastes, the only treatment that has been applied is by a modified design of an American Petroleum Institute type of separator. T h e outlet from the separator becomes one branch of a stream that flows for several miles across the level plains country into a river, one object of the state cleanup program. Only during, and shortly after, very heavy rains, is there other than a very small
Table 1. Flow, Gal./Hr. Max. 740 Min. 60S Av. 676
pH
Settleable Solids
Suspended Solids
9.1 8.0 8.5
0 0 0
80 0 17
Alky] Phenolic Phenols Materials 17.0 Max. 43.0 8.8 Min. 17.5 Av. 29.3 10.9
Dissolved Oxygen B.O.D. 0 0 0
354 93 218
factors to both concentration and flow rate, the daily rate of flow and the concentration of undesirable substances would be covered. With these arrangements installed the sampling and analysis of the waste flow, and the measurement of the rate of flow were started. After some difficulty with certain analytical procedures, data were obtained upon which design could be based with confidence. These data are presented in Table I, as carried out over a 60 day period. Only maximum, minimum, and average figures for the 60-day period are shown. In the first stage treatment, the aim was to remove all oil and suspended matter, leaving a clear solution as material to be cleaned up in the second stage. Thought immediately turned to chemical flocculation, and investigation of the problem by a manufacturer of equipment of this type showed that very good results were obtainable. T h e cost of equipment of the type necessary was found to be rather high when related to the work it was to accomplish, and other procedures were investigated. Among these were a flotation unit, and samples were submitted for test. T h e results
amount of flow in the stream except that resulting from the refinery waste water, until about a mile or so down stream, where it is joined by the outlet flow of a municipal sewage treatment plant. There is ample stream path above this junction, however, to study the refinery outlet carefully for both quality and quantity. Before treatment could be devised it was necessary to know what type of treatment would serve best, and what volume of waste was to be treated. In order to obtain this information, a sampling and measuring station was established at the point that seemed best as a location for the preliminary treatment equipment. Sampling was conducted by means of a continuous sampling device, and the flow was measured with a Parshall Flume. An approach channel was provided for the flume by throwing up earthen embankments. Measurements were taken on the flume throat each hour, and a sample of one carboy (12 gallons) was collected over each 24-hour day. It was realized that in a sample so taken peaks and hollows of concentration would be masked, but as it was planned to apply ample
Dissolved Solids 1880
Flow Rate and Analytical Data Turbidity
716
430 60
956
174
Immediate Oxygen Demand 37.2 0.0 9.4
Immediate Chlorine Demand 576.5 56.8 177.2
Sulfites 329.0 34.8 90.0 Ammonia Nitrogen 70.0 16.6 45.5
Oil 224 43 103 Nitrogen Bases 73.5 46.9 53.7
Sulfides 33.0 0.0 5.6
Dissolved Hydrogen Sulfide 0.6 0.0 0.4
Sulfides and
Mercaptans 2.5.3 1.3
167 74
7.0
96
Alkalinity Cyan ides Alkalinity M.O., (A.P.H.A.) Phenolph . G./Gal. 1 .6 0..4 1..0
VOL. 4 9 , NO. 1
•
Total Sulfides
Chlorides as NaCl, G./Gal. 32.3 17.0 24.9
JANUARY 1957
107 A
I/EC
INDUSTRIAL WASTES
Table II.
Component Alkyl phenols Phenolic materials B.O.D. Intermediate oxygen demand Immediate chlorine demand Ammonia nitrogen Nitrogen bases Cyanides
•
Feature
Reduction in Concentration of Organic Components Conçu. Av. after Pond Conçu., Treatment, % _ P.P.M. Av. P.P.M. Reduction 23 16.7 21.8 4.7 61 12.2 81
218
63
11.4
1.2
90
107.7 67.7 81.1
34.3 36.8 43.3
1.2
0.3
70 45 47 75
were very good, the output from the flotation-type unit containing only 7 p.p.m. of free oil, practically no suspended matter, and only a very slight haze. This haze was readily cleared by bacterial action. Since no increase in volume was necessary, a n d particularly since no chemicals were added to increase the dissolved solids content, this procedure was thought satisfactory for first stage treatment. (Although none of the organic, undesirable, dissolved substances would be reduced to any degree.) Cost d a t a showed t h a t the flotation procedure would require an outlay of about half that for flocculation. T h e floated scum could be destroyed readily by burning it. Although the first stage of the treatment presented no great problem in the removal of the oil and suspended matter, the second stage— elimination of dissolved organic substances, as required by the authorities—presented a challenge. A n u m b e r of procedures were considered but little success was experienced with any of the test runs conducted. T h e state authorities had suggested the use of flocculation, followed by ponding u n d e r conditions that would stimulate n a t u r a l processes of purification. A shallow pond with a surface area of 15 to 20 acres was recommended. As such a pond would effectively eliminate a large area of the most unsightly section of the plant, it was decided to investigate this possibility. A waste of a somewhat similar nature u n d e r study at a research laboratory in Philadelphia, was looked into there. T h e main feature was to pond the waste water and depend upon natural biological processes to eliminate the relatively small amounts of ob108 A
A Workbook
jectionable substances present. It was planned to prepare the outletpoint of the pond as a sedimentation area to provide the greatest degree of clarity readily obtainable prior to discharge. A sample of refinery waste from somewhat, but not exactly similar processing, was obtained, and a flat boxlike structure was prepared. Over the bottom of this box, soil from a field that had not been cultivated in any m a n n e r for years was spread. Care was taken that plant root structures were retained and that some of the smallest plant structures themselves were still present. This area of soil and plant growth, a m o u n t i n g to about 15 sq. feet, was gently watered for one week until the soil was well established and the grasses and small weeds started to show a definite growth. It was then subjected to a slow flow of a mixture of stream water and waste in proportion of 10 to 1 at a rate of 1000 ml. per hour. T h a t this mixture was d a m a g i n g to the plant life at the inlet end of the box was soon obvious, but the growth was not completely destroyed, a n d in about 10 days showed signs of returning to its normal condition. T h e flow was continued at the strength of 10 to 1, stream water to waste, for 10 days before samples were collected, from the outflow collection trough, for analysis. All analytical work followed the procedures recommended by the A P I " M a n u a l for Disposal of Refinery Wastes." Since some trouble was experienced with the procedure for cyanides, and again when the wastes were investigated at the refinery, the methods of the United States Public Health Assoc, publication, "Analysis
INDUSTRIAL AND ENGINEERING CHEMISTRY
of W a t e r a n d Sewage," were employed for cyanides. T h e waste water so treated, however, showed such improvement in its content of objectionable components, (see T a b l e I I ) that it was planned immediately to talk to the state authority about eliminating the flocculation step and installing the soil contact treatment as a final stage treatment for the plant waste flow, greatly reducing the cost of the second stage installation. As is shown, there is no case in which the objectionable c o m p o n e n t is eliminated, and study would be required to establish a timc-of-contact factor to bring a b o u t a degree of concentration reduction that would be satisfactory to the state. Every indication is that practically complete elimination of the objectionable components is possible. T h e r e was one other possibility for disposal—return of the waste water to a point well below any source of water for public or other supply. This type of disposal had been refused, but after considerable discussion, state permission was obtained to use a disposal well and plans for drilling the well now are being prepared. T h e r e are no plans for any cleanu p of the waste prior to injection. It is claimed that other disposal wells in the general area are operating successfully on waste that has not been treated for removal of suspended matter and that no plugging of the formation has resulted. This particular effort to solve a refinery waste problem is worthy ofrecord, to follow its life, to see if a waste carrying suspended matter to the extent of that involved here can be disposed of in a disposal well without plugging the formation and causing considerable expense to keep the disposal system operating and without frequent clean-outs and reworkings of the disposal well. If it does operate without frequent expensive reworking, it will be one among m a n y that have not. Correction. "Standard Methods for the Examination of Water, Sewage, and Industrial Waste," referred to in the third column of page 58 A (November 1956), is a joint publication of the American Public Health Association, the American Water Works Association, and the Federation of Sewage and Industrial Wastes Associations.
