PertanikaJ. Trop. Agric. Sci. 29 (1 & 2): 67-72 (2006)IISS : 1511-3701

©Universiti Putra Malaysia Press

SHORT COMMUNICATION

A Survey of Water Consumption and Product Output fromTen Sago Factories in India

I·A. MANICKAVASAGAN & 2K. THANGAVELlDepartment ofBiosystems Engineering, E2-376 EITC, University ofManitoba,

Winnipeg, ME, Canada R3T 5V6.E-mail: umannama@cc.umanitoba.ca

2Department ofAgricultural Processing, College ofAgricultural Engineering,Tamil Nadu Agricultural University, Coimbatore, India

Keywords: Tapioca effluent, water requirement, product yield

ABSTRAK

Kebanyakan unit pemprosesan ubi kayu India mengasingkan kanji dan sluri dengan menggunakan kaedah enapangraviti. Pengenapan yang berlaku dalam tangki enap membolehkan kontak antara kanji dan air. Proses ini menyebabkanpenapaian berlaku dengan alkohol dan asid organik menjadikan persekitaran tercemar. Sisa air dari kilang pemprosesanubi kayu mengandungi keperluan oksigen kimia yang tinggi (11,077-19,083 mgtl), pH yang rendah (4.33-5.60)dan menyebabkan pencemaran. Efluen daripada industri ubi kayu adalah berasid dan berorganik secara semulajadi, membawa kepada keperluan oksigen biologi pada kadar 1500 hingga 2000gmol). Juzuk-juzuk tak organik sepertifosfat, sulfat, klorida, dan beberapajenis logam terdapat dalam kuantiti surih. Kajian ini menerangkan penggunaanair, output produk, dan penjanaan efluen dalam industri pemprosesan ubi kayu. Kadar yang perlu untuk air adalah4.512 mJ untuk memproses 1000 kg ubi. Apabila ubi-ubi tersebut digunakan untuk pengilangan kanji, 16.7%daripada hasil produk adalah kanji, 1.6% kanji kotor dan 7.0% 'thippi' terhasil dan 18.6% sagu, 1.8% kanjikotor, 19.1 % kupasan dan 3.9% 'thippi' terhasil apabila ubi digunakan untuk pengilangan sagu. Sebanyak 95 %air yang digunakan terhasil sebagai eJluen.

ABSTRACT

Most of the tapioca processing units in India separate starch from slurry by employing the gravity settling method.Sedimentation in settling tanks allows the contact of starch with water. This process leads to fermentation in whichalcohols and organic acids are formed and polluting the environment. Wastewater from tapioca processing factoriescontain high chemical oxygen demand (11,077-19, 083 mg t l), low pH (4.33-5.60) and causes pollution. The effluentfrom tapioca industries is acidic and organic in nature, contributing biological oxygen demand in the range of1500 to2000 g mojo Inorganic constituents like phosphate, sulphate, chloride, and several metals are also found in tracequantities. This paper explains the water consumption, product output and effluent generation in tapioca processingindustries. The average water requirement was 4.512 ml to process 1000 kg ofcassava tubers. When the tubers are usedfor starch manufacture, a product yield of 16. 7% starch, 1.6% dirty starch and 7.0% thippi were obtained, and18.6% sago, 1.8% dirty starch, 19.1 % peel and 3.9% thippi were obtained when the tubers are used for sagomanufacture. About 95 % of the consumed water is leaving the factory as effluent.

INTRODUCTIONTapioca is a productive crop in poor soils andrequires the least labour in cultivation, and can

* Correspondence author

tolerate drought, but the labour requirementin processing after harvest is high(Radhakrishnan, 1996). Dry tapioca rootconsists of 80 to 90% carbohydrate out of

A. MANICKAVASAGAN & K. THANGAVEL

which the most important is starch. Starchcontent in tapioca ranges from 78.1 to 90.1 %on dry basis. Tapioca industry is an agro basedseasonal industry with huge employmentpotential in India. Tapioca is mainly processedinto starch and sago. There are more than1000 tapioca processing units in Indiaproducing starch and sago in cottage and smallscale sectors. The major unit operationsinvolved in sago production are Peeling andwashing, Rasping and pulping, Screening,Settling and purification of starch,Pulverization, Globulation, Sizing, Roasting,Sun drying, Polishing and Packing. The starchand sago factories in India use age-oldtechnology, involving longer duration ofextraction and unhygienic handling of thematerial leading to poor quality end products(Rangaswami, 1993). Padmaja et al. (1990)reported that the starch or sago factories werebecoming obsolete and use oflabour intensiveindigenous technologies, which oftenimparted off colours, offodour and microbialcontamination to starch. Since the enzymaticprocess are likely to develop as soon as theroots were dug up and during manufacture,which ultimately reduces the quality of the endproduct, it is necessary to process the rootsimmediately after harvesting (Grace, 1977).Almost all tapioca processing industries inIndia have two major problems. The firstproblem is the huge requirement of water forbetter extraction ofstarch from tubers. Secondis the generation oflarge volumes of effluent.Many factories are being closed due to theunavailability of water. Hence there is a needfor suitable methods or equipment andtechnology to reduce the water consumptionin tapioca starch production withoutsacrificing the starch extraction efficiency. Itis necessary to have a thorough knowledge onthe different unit operations involved in thestarch production, water requirement, productoutput and effluent generation to developtechnology to solve the water problem. Theobjective of this paper is to quantifY the waterrequirement, product output and effluent

Fig. 1: Addition ojwaterJor washing the tapioca roots

production in the tapioca starch processingindustries.

Conventional Method ofStarch Production

(i) Washing and PeelingRoot tubers are washed manually to removeadhering dirt. The tubers are then cutlongitudinally and transversely to a depthcorresponding to the thickness of the peel,which can be easily removed. Any dirtremaining on the smooth surface of the coreof the tuber is then washed off and the peeledtubers are put in a concrete tank, where theyremain immersed in water until taken out forrasping. The conventional method ofwashingis shown in Fig. 1.

(ii) RaspingThe peeled roots are subjected to high­pressure water jets during conveying forrasping. It is necessary to rupture cell walls inorder to release the starch granules. Rasping

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A SURVEY OF WATER CO SUMPTION AND PRODUCT OUTPUT FROM TEN SAGO FACTORIES I INDIA

Fig. 2: Addition of water while rasping the roots

facilitates rupture of cell walls and release ofstarch granules (Ahmed, 1978). This is carriedout by pressing the roots against a swiftlymoving surface provided with sharpprotrusions. A large quantity ofwater is addedto the roots (Fig. 2) during this process. Thecell walls get ruptured during rasping and thewhole root is turned into a mass in whichsubstantial portions of the starch granules arereleased. It is difficult to remove all the starchin a single operation even with efficientrasping devices. Therefore, the pulp issubjected to a second rasping process afterstraining. Rasping is usually done in machinesusing a wooden roller over which the sheetmetal rasping surfaces are nailed with theburrs facing outward.

(iii) StrainingAfter rasping, the pulp is screened in theshaking screens (Fig. 3). In separating the pulpfrom the free starch, a liberal amount ofwateris added to the pulp as it is delivered by therasper and the resulting dispersion is stirredvigorously before screening. The fresh pulpafter mixing with water in distribution tanks istransferred by pipes to the higher end of thescreen. During screening, the dispersionpasses through a set of screens with increasingfineness, the first one retains the coarse pulp,the others the fine particles. The 'overs' fromthe first screen are returned to the fine raspand then returned for re-screening.

Fig.3: Addition ofwater when strainingthe tapioca pulp

(iv) Settling and Purification of StarchAfte rthe separation of starch by screening, thestarch milk is subjected to a settling process.The starch milk is pumped to a tank fitted witheffluent outlets at varying heights. Settlingtakes about 6 to 20 hours depending on thequantity as well as the size of the settling tank(Radhakrishnan, 1996). Settling is animportant unit operation in cassava processingwhere the extracted starch is separated fromits aqueous dispersion under gravity (Sajeevet ai., 2002). The upper layer ofsediment flour,which has a yellowish green tint, contains manyimpurities and is generally scraped off anddiscarded. The remaining moist flour is thenstirred up with water and transferred toanother tank where starch is settled. The finalsettled moist floor is removed by using a

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A. MANICKAVASAGAN & K. THANGAVEL

crowbar. Sreenarayana et at. (1990) reportedthat a rapid separation ofstarch from the milkand the removal of impurities from thecolloidal material could be achieved bycentrifugation. Hydraulicjack may be used asdewatering technique by putting cassava starchpulp in a bag of woven cloth and subjected tohigh compressive pressure (Igbeka et aL, 1992).

(iv) DryingDrying of starch is generally done by sundrying in the drying yards and then sent forfurther processing for the production ofsago.

(v) Hydrogen Cyanide (HCN) in TapiocaAccording to Mkpong et aL (1990) cited by Zoeet al. (1998), cyanagenic glucosides aresynthesized in the cassava leaves and stored inthe roots. The problems of inherentnutritional hazard (fresh roots contain 50 to400 mg cyanide kg- I root) and highperishability of the roots call for elaborativeprocessing prior to consumption (Chinyere etaL, 1997). The major factor which limits oraffects the utilization of cassava as a food forman is its content of the toxic hydrogencyanide in both free and bound forms (Edijalaet at., 1999). Effective processing can reduceall cyanogens in cassava products to below thesafe level of 10 mg HCN equivalent per kg dryweight set by FAa in 1988 (Mlingi et at., 1995).

(vi) Effluent from Cassava IndustriesBecause of the rapid chemical changesoccurring in the solution ofstarch dispersion,fermentation takes place resulting in theproduction of alcohol and organic acidsespecially butyric acid. Hence the process ofseparation of pure starch from starch milkshould be done without time delay. Wastewaterfrom tapioca processing factories containinghigh chemical oxygen demand (COD)(1l,077-19,083 mg 1-1), and low pH (4.33-5.60)causes water pollution (Hien et at., 1999).Belliappa (1990) found that the effluent fromtapioca industries was acidic and organic in

nature, contributing biological oxygendemand (BOD) in the range of 1500 to 2000g m-3 • He also stated that inorganicconstituents like phosphate, sulphate,chloride, and several metals were also foundin trace quantities. Most factories dispose ofthe effluent into the nearby rivers, streams orlakes. It releases undesirable odour, pollutesthe environment and surface ground water.The volatile solid content estimated for thisindustry effluent was 1.2 (Periasamy, 1996).

MATERIALS AND METHODSThe study was conducted in the tapiocaprocessing units at Namakkal taluk of Rajajidistrict, Tamilnadu, India, where most of thetapioca processing industries in India arepresent. Ten factories of different productioncapacities (15 to 45 ton ofroot per day) wereselected. The water requirement, productoutput and effluent production weremeasured in each factory for three dayscontinuously and the average value recordedfor analysis. For ease and clarity, all values wereexpressed per ton of cassava root.

RESULTS AND DISCUSSIONThe process of extraction of starch fromcassava tubers requires a huge volume ofwater.The wastewater arising out of washing of theroots and the supernatant from the starchsettling tanks constitute the effluent. Theaverage water requirement was 4.512 m3 toprocess one ton of cassava root. Out of this,4.31 m3 and 4.27 m3 of water was released aseffluent, when the tubers were used for starchproduction and sago manufacture respectively.The product output during manufacture ofstarch and sago are shown in the Table 1.When the tubers were used for starchmanufacture, a product yield ofl6.7% starch,1.6% dirty starch and 7.0% thippi wereobtained and 18.6% sago, 1.8% dirty starch,19.1 % peel and 3.9% thippi were obtainedwhen the tubers were used for sagomanufacture. In both processes, about 95% of

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A SURVEY OF WATER CONSUMPTIO AND PRODUCT OUTPUT FROM TE SAGO FACTORIES I I DIA

TABLE 1Water consumption and product output in sago factory (mean of 10 factories)

Raw Material

Product

Cassava rootWater

Output - During Manufacture of Starch

Quantity

1 ton4.512 m 3

cv

7.3

Product

StarchDirty starchThippi (Dried)

Effluent

Output - During Manufacture of Sago

Product

SagoDirty starchPeelThippi (Dried)Effluent

the consumed water is coming out as effluent.Since each factory is using different types ofmachinery, there was a variation in productoutput between the factories. The coefficientofvariation (CV) in the product output rangedbetween 6.9 and 13.7 in starch themanufacturing process and between 8.3 and13.6 in the sago manufacturing process. Inboth cases, the CV was less for effluentgeneration. The pattern of effluentproduction was almost similar in all factorieswhen compared to other products. Since thequality ofwaste water released from the starchsettling tank is not suitable for reuse in theproduction process, almost all factories arefacing severe problems in treating the huge

Quantity CV

167.40 kg 9.716.32 kg 9.969.65 kg 13.7

4.310 m 3 6.9

Quantity CV

186.14 kg 13.618.32 kg 13.2

190.53 kg 8.538.60 kg 8.5

4.272 m 3 8.3

volume of effluent. Quick separation of waterfrom starch milk in the settling tank will retardthe deterioration in water and hence thereleased water may be reused in theproduction process. The dual problems (highwater requirement and effluent production)in the starch factories may be solved by thequick separation ofwater from the starch milkwith the help of equipment and reusing thewater in the production. A solid-liquidseparation equipment such as, hydrocyclonemay be used for the quick separation in orderto replace the conventional gravity settlingmethod.

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