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T.C

CANAKKALE 18 MART UNIVERSITY

FACULTY OF ENGINEERING

ENVIRONMENTAL ENGINEERING

INDUSTRIAL WASTEWATER TREATMENT

Subject: TREATMENT OF THE SUGAR INDUSTRIAL WASTEWATERS

Supervisor:

Prof. Dr. NİLGÜN ÖZ YAMAN

GÖZDE OZAN

120405034

ABSTRACT

Sugar industries important play role in the Turkey economic development. However, the wastewater produced from sugar industries stand at a high rate of pollution load. Sugar industries in Turkey compose 15 to 20 m3 of wastewater for 1 ton of sugar cane crushed. Wastewater from these industry, if discharged without treatment, constitute pollution problems in both aquatic and terrestrial ecosystems. In this paper, basic information about the sugar industry and its waste, sources and characteristics, manufacturing process, water consumption, and treatment of wastes from sugar industry will be carried out. Most of the research work for sugar industry wastewater treatments has been carried out by anaerobic treatment processes. On the other hand, in anaerobic process cannot easily degrade oil and grease. Also, an anaerobic process partly degrades nutrients whereas, aerobic processes consume higher energy. Anaerobic-aerobic combined systems can remove organics completely. However, anaerobic-aerobic combined systems were carried out by few studies.

Keywords: Sugar industry; Sugar industry wastewater and their sources and characteristics; Aerobic treatment; Anaerobic treatment; Physico-chemical treatment

INDEX

ABSTRACT 2

1. INTRODUCTION: 4

Table1.1: Top Ten Sugar Beet Producers-2013 4

2. MANUFACTURING PROCESS: 4

Sugar production- step by step 4

Table 2.1 Flow diagram of cane sugar manufacturing process 6

Table 2.2 Flow diagram of beet sugar manufacturing process 6

3. WATER CONSUMPTION IN THE SUGAR INDUSTRY 6

Table 3.1: Water Consumption 7

4. SOURCES OF WASTEWATER AND CHARACTERISTICS 7

5. TREATMENT OF THE WASTES 7

Table 5.1 Flow diagram of complete treatment of sugar industry wastewater for aerobic condition 8

Table 5.2 Flow diagram of complete treatment of sugar industry wastewater for anaerobic condition 8

6. TREATMENT METHODS 8

6.1 Biological methods 8

6.1.1 Anaerobic treatment 8

6.1.2 Aerobic treatment 9

6.1.3 Physico-chemical methods 10

7. CONCLUSION: 11

8. SOURCES: 11

1. INTRODUCTION:

 Sugar can be produce from beet or from sugar cane. In turkey, sugar mainly produce from beet. Sugar industry important play roles in the Turkey economic development  

Rank Country Production

(million tonnes)

1 Russia

39.2

2 France

33.6

3 United States

29.8

4 Germany

22.8

5 Turkey

16.5

6 China

12.1

7 Ukraine

10.8

8 Poland

10.6

9 Egypt

10.0

10 United Kingdom

8.0

Total World 250.2

Table1.1: Top Ten Sugar Beet Producers-2013 Source: UN Food & Agriculture Organisation (FAO)

Table1.1 shows that top ten sugar beet producers in 2013.

Turkey has major role to produce sugar in the world. As a result of producing sugar the wastewater However, the wastewater produced from sugar industries stand at a high rate of pollution load.

However, sugar industry is basically seasonal in nature and operates only for 150–210 days in a year (November to May).

2. MANUFACTURING PROCESS:

Sugar production- step by step

The beet seeds sour in March and April and grow up to harvest time. The sugar founding beat is produced from the Rays of the Sun, water and CO2 in a process called photosynthesis. A sugar beet usually contains 80 to 90 % sugar. Harvesting normally starts in mid-September and March the begging of the hundred to hundred and 20 day sugar productions season known as the beet company. Large beat harvesters are used to lift the beat carefully out of the ground and loaded for transport to the sugar factory.

At the sugar factory, the beat is weighted and samples taken to measure the sugar content and amount of soil and stones present in the load.

The beat is transported to the washing area. Large quantities of water used to wash and handle the beat. Approximately fifty thousand cubic meters of water each day. Sugar beet contains 85% water. Water that should be clean and reuse again and again.

A conveyor belt carries the clean beet to the slicing machine where it is cut into thin strips. The strips are taken to a diffusion device where the sugar is extracted in hot water at a temperature 70 oC. The resulting liquid is called raw juice. The remaining beat strips called beet pulp oppressed and used fiber products as the beet pulp dries the water that evaporates is released a stream via the factory chimneys.

Purification of the raw juice takes places by adding slake lime CO2 to bind non-sugar substrate. Once this substrate are filtered off a pale yellow juice in juice remaining with sugar content of around 40%. The rest is mainly water. The filtered off lime is pressed and soldiers soil conditioner.

Most of the remaining water is removed by evaporation in large vessels. Thick juice is left behind now containing approximately 80% sugar. Because thick juice still contains too much water. This water is removed almost entirely by boiling at low pressure.

It is important that temperature does not exceed 80 oC. Otherwise the sugar may caramelize and it burnt.

The thick juice is now sufficiently concentrated for crystals form. A small amount of sugar is added to start the crystallization process. Just a hundred grams are required to make 20 to 25 tons of sugar. The produces a mixture of sugar crystals and syrup.   

Sugar is separated from the masakit in a centrifuge. The process of boiling and centrifugation is repeated until no more sugar can be extracted.

The water sugar is carefully washed out scraped from the centrifuge, and dried and saved. This is the final sugar product.  Table 2.1 Flow diagram of cane sugar manufacturing process

Table 2.2 Flow diagram of beet sugar manufacturing process

3. WATER CONSUMPTION IN THE SUGAR INDUSTRY

In the sugar industry average 15 to 20 m3 of water is used in order to get 1ton of beet. In fact, about 70% of sugarcane is water and, therefore for every ton of sugarcane that is crushed, 700 Liters of water is generated, of which 500 Liters is utilized in the factory.

Table1, 1 that shows where water use at factory and how much water is consumed. As we clearly can see that most of water use in the sugar industry are flotation and washing which are able to reuse again.

Recently, to establishing the closed water system, wastewater is degraded 15 m3/ ton to 0.8 m3/ ton. However, some of water use are possible to reuse again at factory which are picking beets at the factory, washing of beets, other uses (cooling of pumps and machines).

Places of water usage at factory Water consumption

Flotation and washing

-picking beets at the factory

-washing of beets 5−8 m3/ton sugar beet

1.5−2 m3/ton

Diffusion 0.4−0.6 m3/ton

Evaporation 4−8 m3/ton

Power generation 0.03−0.04 m3/ton

Lime preparation (production of milk of lime) 0.07−0.1 m3/ton

Other uses (cooling of pumps and machines) 0.4−0.5 m3/ton

Filter cloth washing 0.03−0.06 m3/ton

Factory cleaning 0.02−0.03 m3/ton

Table 3.1: Water Consumption Source: (Perendeci ve Süral 2004)

4. SOURCES OF WASTEWATER AND CHARACTERISTICS

A significantly large volume of waste is generated during the manufacture of sugar and contains a high amount of pollution load, particularly in terms of suspended solids, organic matter, and press mud, bagasse and air pollutants.

• The wastewater from mill house include the water used as splashes to extract maximum amount of juice and those used to cool the roller bearings.  

– This wastewater contains high BOD due to presence of sugar and oil and grease from machineries.  

• The wastewater from occasional washing of filter cloths (used for filtering the juice) though small in volume, contains high BOD and SS.  

The water used for cooling in evaporators also contributes as wastewater. The cooling water gets polluted as it picks up some organic substances from the vapors of boiling syrup in evaporators and vacuum pan.

– Although this water is recirculated it is required to be discharged. This contributes to considerable volume of waste and moderate BOD.   

• Additional waste originates due to the leakages and spillages of juice, syrup and molasses in different sections, and also during handling of molasses. Washing of floor (periodic) contributes a lot to pollution load. Though, it is small in volume, strong in BOD concentration.   

• Periodic blow-off of the boilers produce another intermittent waste discharge. This is high in SS, low in BOD and usually alkaline.

5. TREATMENT OF THE WASTES

Way to reduce the pollution load

• In sugar mills, pollution load can be reduced and material economy performed in plant.   

• Recycling will minimize the volume of waste to a large extent. For example, volume of mill house waste can be decreased by recycling the water.   

• The volume of waste can be reduced used for floor cleaning and reducing quantity of floor wash

• Convenient control of operation can reduce the pollution load. For example, overloading of evaporators and vacuum pans, extensive boiling of the syrup leads to loss of sugar through condenser water thus increase in volume and strength of effluent.

Table 5.1 Flow diagram of complete treatment of sugar industry wastewater for aerobic condition

Table 5.2 Flow diagram of complete treatment of sugar industry wastewater for anaerobic condition

6. TREATMENT METHODS

Screening, grit removal, flow equalization, sedimentation, or dissolved air flotation are used to reduce suspended solids load from sugar industry wastewater. Biological treatment includes aerobic and anaerobic process. Except biological methods, physico-chemical methods are also used for sugar industry wastewater treatment.

6.1 Biological methods

Sugars and volatile fatty acids which are easily biodegradable. Mostly it can be found in sugar industry wastewater. Therefore, anaerobic and aerobic treatment processes are most appropriate. As a result of many studies Table 3 shows summary of the studies about biological treatment for sugar industry wastewater treatment.

6.1.1 Anaerobic treatment

Treatment method Opportunities Limitations

Anaerobic •Small reactor size

•Less energy required

•Excess sludge low

•Up to 90% of VSS removal

• Energy production

• High COD loading

• Effluent quality good (in terms of COD) •Oil and grease are not easily reduced

• Partly degrades organics

• Post-treatment is often required in terms of effluent

Anaerobic treatment method in sugar industry is generally used for concentrated wastewater, in terms of pollutants. Anaerobic treatment has many advantages over aerobic processes. It includes the lesser energy required, methane production due to the degradation of organic matter. Anaerobic treatment is source of energy; and lesser sludge production, which indirectly reduces sludge disposal costs greatly [24–26].

6.1.2 Aerobic treatment

Aerobic • Aerated submerged fixed-film (ASFF) process can be use severe organic loading

•Excellent effluent quality (in terms of COD, BOD, and nutrient removal)

• Aerobic-SBR high removal of organics for different industrial wastewater. Therefore, it may be a good option for the sugar industry wastewater treatment.

 •Aerobic SBR small area is needed to be compared to other aerobic activated sludge processes • Excess sludge produced is high

• Require larger area

• Odor problem occurs during the treatment process using lagoons

• None of the studies available reports complete removal of organics

• Aerobic SBR treatment systems need more controlling

Aerobic biological treatment generally includes degradation of organics in the existence of oxygen. Conventional aerobic treatment contains activated sludge, trickling filters, aerated lagoons, or a combination of these [39]. Sugar industry wastewaters are biodegradable in terms of COD/BOD. However, sugar industry contains oil and grease which are not easily reduced by anaerobic processes, because some study were reported that oils produce long-chain fatty acids during the hydrolysis step which causes retardation in methane production. [42].

Earlier, lagoons were used for sugar industry wastewater treatment [44,10] because of economical. Besides being an economical, it needs larger area and emission of unpleasant and odor during the treatment process. These some of the disadvantages of lagoons were reported. Aerated lagoons were also used in the past, and showed lesser residence time and area required compared to lagoons, to treat sugar industry wastewater, but oxygen consumption and HRT were found to be high, and still large area requirement is disadvantage [10].

In this case none of the studies showed almost complete organics’ removal. Therefore, an additional biological treatment phase is needed. Hybrid systems of comprising anaerobic and aerobic treatments have been approved capable of giving high COD removal efficiency with smaller required energy [5,10,14]. Yang et al. [48] reported a combined anaerobic (UASB) and aerobic (EAFB) treatment system for effluent from primary treatment of sugarcane mill wastewater for its application for drip irrigation, and P 99% organics and solids removal were reported at HRT of 2d. This treated wastewater hold better water quality for drip irrigation.

6.1.3Physico-chemical methods

Physicochemical • Combined system of coagulation with adsorption, removal efficiency of BOD and COD high

•In electro-oxidation method, there is no generation of secondary pollutants.

•Electro-oxidation better treatment compared to the electro-coagulation •Chemical coagulation/flocculation process generates secondary pollutants

•In electro-coagulation process need to be regularly replaced (electrodes can be dissolved into wastewater due to oxidation)

•The efficiency of electrocoagulation process may decreased as a result of  a layer of electrode material oxide is deposited over the cathode leading

• Electro-coagulation may be contaminated with electrode material

Coagulation/flocculation with inorganic coagulants and adsorption are widely used for the removal of suspended, colloidal, and dissolved solids (DS) from wastewaters. Generally, coagulation/flocculation is used in the primary purification of industrial wastewater. In coagulation process, insoluble particles and/or dissolved organic materials aggregate to be larger, and are removed by sedimentation/filtration stages. BOD and COD removal efficiency was reported to be 96 and 95%, respectively.

Scientist researched electro-oxidation and electro-coagulation, ion-exchange process wastewater from a sugar refinery at different values.

At 5A in 7h electrolysis time, eloctro- oxidation method showed 99.9, 90.5% and 63.1, and of decolorization, TSS removal, COD removal respectively. Whereas, at 5A in 8h electrolysis time in electro-coagulation 97.4%, 71.2, 18.5, and of TSS removal, decolorization, COD removal respectively, were found. According the this study, EO was finalized as the better treatment alternative in comparison to electro-coagulation not only in terms of removal, but also in terms of energy cost.

7. CONCLUSION:

In this paper, basic information about the sugar industry and its waste, sources and characteristics, manufacturing process, water consumption, and treatment of wastes from sugar industry were reported. As a result of analysis of many studies, these results have been reached.

•In sugar industry, wastewater is biodegradable according the COD/BOD ratio. (1.6 - 2)

•Many studies show that conventional aerobic treatment (ASP and TF) are not too efficient

•The sugar industry is basically seasonal in nature and operates only for 150–210 days in a year. Operation of sugar industry (for example, conventional treatment) will be costly

• Efficiency of anaerobic treatment (digestion and lagoon) about 70% to 90% .Effluent from anaerobic treatment can be treated by stabilization pond.

• Two stage biological treatments (anaerobic lagoon + stabilization pond) is generally used. Because overall BOD can be removed about 90%.

8. SOURCES:

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