Sugar Cane Process Wastes

Sugar Cane Process WastesAuthor(s): Ralph StoneSource: Sewage and Industrial Wastes, Vol. 23, No. 8 (Aug., 1951), pp. 1025-1028Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25031665 .

Accessed: 15/06/2014 16:04

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

Water Environment Federation is collaborating with JSTOR to digitize, preserve and extend access to Sewageand Industrial Wastes.

http://www.jstor.org

This content downloaded from 188.72.126.108 on Sun, 15 Jun 2014 16:04:09 PMAll use subject to JSTOR Terms and Conditions

http://www.jstor.org/action/showPublisher?publisherCode=wef

http://www.jstor.org/stable/25031665?origin=JSTOR-pdf

http://www.jstor.org/page/info/about/policies/terms.jsp


SUGAR CANE PROCESS WASTES By Ralph Stone

Sanitary Engineer, Los Angeles, Calif.

Sugar Cane Milling Processes

Sugar cane requires 18 months of

growth before harvesting. When the cane stalks have a satisfactory sugar content, they are cut down and trans

ported within a few hours to a sugar cane mill. There the stalks are

squeezed in rotary extractors to re lease the sap containing the sucrose

(CijjH^Ou). Refined sucrose is our common table sugar. The cellulose residue (Figure 1) is dried out by air

storage in a shed, and then burned to .

provide the heat energy for steam boilers and auxiliary power required in sugar manufacturing.

The squeezed sap is purified by skimming off the floating matter, called

"cachaza"; evaporation of the excess

water; and separation of the black

strap molasses. Sulfur is added to

provide a whiter final sugar product and small quantities of lime are em

ployed for pH control. The surface

skimming "cachaza" can be placed through a pressure or vacuum type filter to reclaim additional sugar sap. The fibrous filter residue is returned

to the fields as fertilizer. Similiarly, the blackstrap molasses can be con verted into alcohol and numerous other by-products or may be fed di

rectly to cattle. Even the ash from the burned cellulose residue employed as fuel is valuable for agricultural fertilizer. Boiler water and waste

wash water from the sugar cane mill are needed for irrigation of the cane

fields. It can be seen from this description

of the sugar cane processing that all the waste products resulting from the

production of sugar cane can and, should be re-employed as a source of

fuel, fertilizer, by-products, or irriga tion water. Hence, the intelligently designed and operated cane mills should not have waste pollution prob lems and should provide the highest operating efficiency and monetary profits.

Cauca Valley Pollution Survey

A stream pollution survey of the Cauca Valley, in Colombia, South

America, during July and August,

Cane Fields

Cachaza Fertilizer Sulfur

for Bleach

Lime for pH Control

Cane Squeezing

i?

Dried Stalks

Squeezed Juice

L1T21J _E^L^^-fJ?i??r

Irrigation Water

. Steam for H*! Heat and

Power

Recovered Juice

Filter

Purification

and

Crystallization

Products

I

^ Waste l*_ --I Water

~

Skimming Cachaza

Sugar

Molasses

Alcohol etc.

|

FIGURE 1.?Flow diagram of sugar mill operations, showing utilization and conservation of sugar, by-products, and waste water to minimize pollution of surface waters.

1025



1026 SEWAGE AND INDUSTRIAL WASTES August, 1951

1950, demonstrated that the five-fold increase in cane production during the

preceding decade has resulted in pol lutional problems. In general, pollu tional complaints had been based on

taste, odor, and dead fish ; no attention was paid to the presence of pathogenic bacteria, which were accepted as a

matter of course.

Special field sampling equipment was employed for taking bacteriologi cal, dissolved oxygen, B.O.D., and chemical samples for laboratory analy sis. The refrigerated bottles of wa

ter and wastes were transported to the Cali water works laboratory for im

mediate examination. Samples that could not be analyzed in Cali were

flown to the National Sanitary Labo

ratory of the Ministry of Hygiene in

Bogota, where the laboratory work was terminated. Standard methods and modern scientific laboratory

equipment were employed in perform ing the analysis of the various cane

wastes, river waters, and sewage sam

ples.

The field investigations indicated

that sugar mills were the responsible agents for the pollution of the Parraga

and Guabas Rivers. Because of the

discharge of the sugar cane skimmings (cachaza) and plant wash water, the

Parraga River samples had a B.O.D. of more than 113 p.p.m. It was found that the Castilla sugar mill supplied over one-half the low flow of the Par

raga River. Similarly, although the Pichichi sugar mill attempted to con

trol its industrial waste waters by

lagooning and irrigation, at certain

times in the past there had been over

flows which had contaminated the

Guabas River basin.

The city of Cali discharges raw sew

age into the Cali River in volumes

great enough so that it represents 50

per cent of the low flow. However, the details on sewage pollution of the

Cauca Valley are outside the scope of

this paper. Besides the sugar mills mentioned,

other sugar cane plants surveyed in

cluded Manuelita, Mayaguez, and

Providencia. Numerous small and old

fashioned cane mills were also visited, but it was found that they do not pre sent a pollution problem because of

non-wasteful operating practices.

FIGURE 2.?Some mills reclaim sugar from cachaza in filter presses. to fields as fertilizer.

Cake is returned



Vol. 23, No. 8 SUGAR CANE PROCESS WASTES 1027

FIGURE 3.?Reclamation of sugar from cachaza by vacuum filters permits chuting of cake to open cars for disposal in fields as fertilizer.

Laboratory Results

It was found that the industrial waste waters of the modern sugar

mills varied in B.O.D. content from 140 to 1,120 p.p.m. This effluent could be maintained at lower B.O.D. levels by more efficient plant operation, including the reclamation of sugar from cachaza through filtration (Fig ures 2 and 3). For example, the

Castilla sugar mill wasted more than

440,000 lb. of sugar a year through di

rect disposal of the cachaza into the

waste-water effluent. Similarly, the

high B.O.D. of the Pichichi mill waste

effluent is indicative of huge sugar

wastage.

Besides cachaza, valuable molasses

is sometimes wasted. The cachaza had

a B.O.D. content in the range of 85,000 p.p.m., but the molasses B.O.D. was

more than ten times as great with 930, 000 p.p.m. The strong pollution pos sible from such materials is evident. It also is interesting to note the pres ence of grease in some of the samples (10 to 6,640 p.p.m.) : the grease can

be explained as the result of wastage from machinery lubrication in the

sugar manufacturing plant. Table I

contains a short summary of important laboratory analyses of samplings.

The operating efficiency will de

termine the amount of water required

by a sugar mill to process a stated

quantity of sugar cane. The more ef

ficient plants require less water (1.32 to 1.55 c.f.s. per 100 tons of sugar



1028 SEWAGE AND INDUSTRIAL WASTES August, 1951

TABLE I.?Summary of Important Chemical arid Bacteriological

Analyses of Sugar Mill Wastes and Receiving Waters

Mill Sample B.O.D. (p.p.m.)

Total Solids (p.p.m.)

E. coli (M.P.N./ 100 ml.)

Castilla

Pichichi Mayaguez

Providencia

Manuelita

Cachaza and waste water

Parraga River, upstream

Parraga River, downstream

Waste water

Waste water

Cachaza

Molasses

Waste water

Waste water

Molasses

473

113 1,120

140 84,700

930,000 250

917 261 361

2,302 144 178

290 165,970

3,800 9,500

1,300

cane) than the less efficient plants (1.77 to 2.64 c.f.s. per 100 tons of

sugar cane). Similarly, whereas the inef?icient mills will produce 8 tons of

sugar and 1.4 tons of molasses per 100 tons of raw cane, the more efficient

mills will produce 12.5 tons of sugar and 2.5 tons of molasses per 100 tons of raw cane (see Table II).

Summary and Conclusions

1. Samples of sugar mill waste ef fluents contained from 140 to 1,120 p.p.m. B.O.D., depending on the op

erating efficiency of the plant. An ef ficient sugar mill utilizes and con serves almost all the sugar, by-prod ucts, and waste water, resulting in minimum pollution of surface waters.

2. Sugar mills should filter the high B.O.D. cachaza waste skimmings, so as

TABLE IL?Comparison of Sugar Mill Operation Characteristics

Mill

Average

100 ion per of Cane

Molasses

1.4

2.3

2.5

0.8

1.6

1.7

Water Use per 100 Tons of

Cane (c.f.s.)

1.77

1.33

2.63

1.55

1.82

Molasses per 100 Tons of

Sugar (tons)

17.5

18.5

19

8

12.8

15.2

Sugar

Castilla Providencia

Pichichi Mayaguez Manuefita

8.0

12.5

9.9

10.0

12.5

(toi

Sugar

icia

ez

ta

8.0

12.5

9.9

10.0

12.5

10.6

to reclaim the sugar and fertilizer. available. This cachaza has a B.O.D. of about 85,000 p.p.m.

3. Molasses should be used for cat tle feed, or in the production of alcohol and other by-products, rather then

wasted to streams. Molasses B.O.D. is greater then 900,000 p.p.m.

4. Sugar mills should be located so

that the waste waters can be employed to irrigate the surrounding cane fields.

5. The squeezed cane stalks are

available for fuel to provide power and heat in the sugar mill. The ashes and filtered cachaza wastes are excel lent fertilizer for the cane fields.

6. It is economically advisable to conserve the valuable cane sugar and

by-products, rather than to dispose of them into and pollute the neighboring streams. Sugar cane waste pollution is the result of poor plant engineering and/or bad mill operation.

Acknowledgments

The help of many Colombian engi neers including the assistance of offi cials of the Colombian Ministry of Hy giene and the Institute of Inter-Ameri can Affairs is acknowledged. Particu lar thanks are due Dr. Hernando

Correal, chief, National Sanitary Lab

oratory, who supervised the analytical laboratory work, and Manuel Escal?n, Sanitary Engineer, who helped in the field sampling and correlation of data.



Documents

Sugar Cane Process Wastes