MONITORING OF SUGAR LOSSES IN THE FACTORY WASTEWATER STREAMS

Maribel P. Alvarez

The Sugarcane Plant

Composition of Sugarcane and Juice Solids Millable Cane Cane (%) Water 73 – 76 Solids 24 – 27

Soluble Solids 10 – 16 Fiber (dry) 11 – 16

Millable Cane Juice Constituents Soluble Solids (%) Sugars 75 – 92

Sucrose 70 – 88 Glucose 2 – 4 Fructose 2 – 4

Salts 3.0 – 4.5 Inorganic acids 1.5 – 4.5 Organic acids 1.0 – 3.0

Organic acids 1.5 – 5.5 Carboxylic acids 1.1 – 3.0 Amino acids 0.5 – 2.5

Other organic nonsugars Protein 0.5 – 0.6 Starch 0.001 – 0.100 Gums 0.30 – 0.60 Waxes, fats, phosphatides 0.05 – 0.15

Other 3.0 – 5.0

How Contamination of Sugar Affect the Wastewater BOD5 Concentration Republic Act No. 9275 March 22, 2004

ARTICLE 1 DECLARATION OF PRINCIPLES AND POLICIES SECTION1. Short Title.- this Act shall be known as the “Philippine Clean Water Act of 2004.”

TABLE 2A- EFFLUENT STANDARDS: Conventional and Other Pollutants in Protected Waters Category I & II and Inland Waters Class CA

PARAMETER INLAND

WATERS CLASS C

OEL (mg/L)

N P I (mg/L)

pH (range) 6.0-9.0 6.5-9.0 5-DAY 20 OC BOD 80 50 TOTAL SUSPENDED SOLIDS

90 50

OIL & GREASE (Petroleum Ether Extract)

10.0 5.0

Biochemical oxygen demand (BOD)

Biochemical oxygen demand (BOD), the amount of dissolved oxygen used by

microorganisms in the biological process of metabolizing organic matter in the water. The more organic matter there is (e.g., in sewage and polluted bodies of water), the greater the BOD; and the greater the BOD, the lower the amount of dissolved oxygen available for higher animals such as fishes.

The BOD is therefore a reliable gauge of the organic pollution of a body of water. One of

the main reasons for treating wastewater prior to its discharge into a water resource is to lower its BOD- i.e., reduce its need of oxygen and thereby lessen its demand from the streams, lakes, rivers, or estuaries into which it is released.

Biological Processes

*Using microorganisms to turn organic matter into CO2 and more microorganisms

through RESPIRATION and SYNTHESIS.

+ Food + Oxygen (O2) (O2) + more

Food, Air, & ‘Bugs’

Effective Methods developed by BUSCO

• Development of a close-loop system • Performance of a sugar monitoring to minimize product loss • Use of wastewater for irrigation

BUSCO SUGAR MILLING CO., INC.

Warm Condenser Injection Water is being cooled using the Spray pond handling both the Raw house and the refinery and re-use it back as injection water. The spray pond has a total cooling capacity of 350m3/min. It cools down from 42-450C to 300C.

How Sugar Contaminates the Boiler Feed and Condenser Cooling Water

The feed water for the steam boilers in a cane sugar factory is largely derived from the water that is evaporated from the juice and syrup. The water from the steam condensed of the first vessel of the multiple effects, the calandrias and coils of the vacuum pans, and the coils and tubes of various heaters forms a highly important source of water supply for boilers. Sugar may enter these waters through entrainment with the vapors from the juice and syrup and through defects that develop in the heating surfaces.

The data below were the average BOD5 concentration which paves a way for monitoring sucrose loss to wastewater entering the WWTP of the company.

BOD5 (mg/L) of Busco Wastewater Tributaries

• The BOD5 in 2003 to 2005 were high as a result of unawareness of sugar losses going to sewer.

• By 2006 the results are still high making treatment difficult and expensive.

Simplified Wastewater Flow Diagram for Raw Sugar Factory

• Sugar is one of the primary sources of BOD5 in a sugar factory. The reduction or minimization of its loss is a direct influence to the reduction of pollutants in the effluent measured by BOD5

CHARACTERIZATION OF BUSCO WASTEWATER INFLUENT

PHYSICAL PROPERTIES

LABORATORIES MILL RAW PROCESS

REFINERY PROCESS

COLOR Caustic Soda Washing of evaporators & Vacuum Pans

IER Regeneration washings

SOLIDS Bagasse Lime, filter cake

Mud cake, Decalite, Resin, Carbon

TEMPERATURE Condensate caustic soda washings

CHEMICAL CONSTITUENTS ORGANIC: CARBOHYDRATES/ SUGAR DISCHARGED TO SEWER

Spilled Sugar Samples

Juices from tank, overflows, Imbibition water

Condenser Water Entrainment from Evaporators and Vacuum Pans Condensate from Heaters and evaporators Leakages from filters, filter cake, washings, sugar spillages

Condenser Water Entrainment from Evaporators and Vacuum Pans Condensate from Heaters and evaporators Leakages from filters, mud cake washing, Sugar spillage from

from conveyors and floors, pump leaks, tank overflows, Caustic Soda Washing of Evaporators & Vacuum Pans

conveyor and floors, pump leaks, tank overflow, Caustic Soda Washings of IER, Sugar dust going to sewer during rainfall due to inefficient sugar dust collecting system.

Heavy Metals Lead from Clarification of sugar samples

pH Low pH of spilled juices

High pH of caustic soda washings and lime spillages

High pH of IER washings and milk of lime spillages

SUGARCANE PROCESSING CONTROL MEASURES BY WASTE MINIMIZATION

CLOSE LOOPING OF BAROMETRIC CONDENSER INJECTION WATER TO BOTH

THE RAW MILLAND REFINERY

Warm Condenser Injection Water is being cooled using the Spray pond handling both the Raw house and the refinery and re-used it back as injection water. The spray pond has a total cooling capacity of 350m3/mi

CLOSE LOOPING OF EQUIPMENT COOLING WATER SYSTEM

The equipment cooling water are being retrieved and

recycled with the use of several cooling towers covering; Mills, Boilers, Power House, Process/Boiling House, and the Refinery Molasses cooling water, continuous vertical crystallizer (CVC) cooling, and Refinery vacuum pump sealing water is also re- used using cooling towers.

BUSCO SUGAR MILLING CO., INC.

Cooling Tower #1 Capacity – 400cu./hr. Type – Cross Flow Make – Hitache Zozen

Cooling Tower # 2 Capacity – 400cu./hr. Type – Cross Flow Make – Marley

Cooling Tower

Cooling Tower #1 & 2 are supplying cooling water for Mills, Power house and Boiler equipment and machineries such as Roller Mills. Turbine oil coolers, IDF and FDF Drive Cooler and other equipments. Temperature range – 40oC to 30oC

Cooling Tower # 3 Capacity – 45.5cu./hr. Type – Cross Flow Bottle Make – Liang Chi

Cooling Tower # 4 & 5 Capacity – 400cu./hr. Type – Cross Flow

Bottle Make – King Sun

Cooling Tower # 3 supplies cooling tower for Mills Hydraulic Hagglund drives Cooling Tower # 4 supplies cooling and sealing water for Raw and Refinery Vacuum Pumps Cooling Tower # 5 supplies cooling water for Molasses and continuous vertical crystallizer (CVC)

WASTE MINIMIZATION

Continual effort on waste minimization is undertaken in all level. Sufficient recovery pump had been installed to recover material and minimized waste from Mill to process and Refinery.

Installation of CONDENSER WATER OVERFLOW TANK

C o n s i d e r i n g t h e

volume of condenser water being handled by the p u m p i n g s t a t i o n s a n d considering the potential p o w e r o u t a g e s d u r i n g operations for whatever reasons, a condenser water overflow tank was installed with a capacity enough to handle the condenser water

volume from the pipelines that may fall down and eventually overflow from the canal system at any given time. Thus, with the condenser overflow tank, condenser water is totally prevented at any given time if there will be power outages to overflow into the river.

RECOVERY OF BAGASSE LEACHATE

Bagasse leachate from the storage of bagasse at the bagasse house especially those that are

stored outside the bagasse house are collected and treated at the WWTP to prevent spilling at the river considering the river is located just below the bagasse house.

Collection system was designed just for the purpose to prevent it from flowing to the river.

A clearance from the Factory fence was maintained and several canals with pumping stations were made to ensure total collections.

BAGASSE LEACHATE COLLECTION

Bagasse collection system was constructed and installed in

order to collect the leachate and have it sent to the WWTP in order to be treated before recycling or discharged.

Another view of the Bagasse Leachate Collection System showing the partition wall as well as the Pulangi river.

TREATED WASTEWATER USED AS SUPPLY AND MAKE-UP TO INDUSTRIAL WATER NEEDS

Scrubbing water to all boilers is supplied from the treated wastewater. Its make-up water due to absorption to the ash is also supplied from the treated wastewater.

ATTAINING SODIUM PRESENCE WITHIN ALLOWABLE LIMITS FOR IRRIGATION

To attain the sodium presence within the allowable limits for irrigation and considering the refinery is using brine in its process, a brine separator was installed at the refinery. The spent regenerating chemicals or retentate of the ion exchange resin (ER) is recovered thru the NANO Filtration process. The resulting product or permeate is reused as regenerating agent for the IER reducing the quantity of industrial salt usage of the refinery.

Another view of the Bagasse Leachate Collection System showing the retrieval pump #3 and the Overflow Condenser Water Tank.

RE-USE OF TREATED WASTEWATER

As irrigation water to cane farm

Treated wastewater is re-used as irrigation water to the Busco Cane Farm area, adjacent to the Mill Site (Busco Owned) 493 hectares, leased area adjacent to the Mill and sub-leased to others 323 hectares with a total of 816 hectares.

The irrigation system is a hand move spray irrigation system that uses aluminum pipes

backed by centrifugal pumps and spray nozzles. This irrigation system will provide enough water requirements (.e. 8mm/day) to the sugarcane planted in the area for better production yield.

MONITORING OF VAPOR FOR SUGAR

The most dangerous source of entrainment loss is in the evaporator or vacuum pan condensers. The BOD5 of carbohydrate according to Bevan and Stevenson is in the ratio of:

BOD5 1ppm= carbohydrate 0.833 ppm

Table: Mineral constituents in sugar cane juices, syrup and molasses

Constituent

Concentration (% solids)

Raw Juice Clarified juice Syrup Molasses

Potassium (K2O) 0.4-2.0 0.3-1.0 0.7-1.0 2.3-6.5 Sodium (Na2O) 0.3-0.10 0.03-0.09 0.02-0.04 0.03-0.06 Sulfate (SO3) 0.11-0.52 0.16-0.44 0.20-0.61 1.10-3.39 Chloride (C1) 0.10-0.29 0.10-0.26 0.16-0.46 0.13-1.11 Calcium (CaO) 0.17-0.32 0.27-0.55 0.35-0.37 0.86-1.64 Magnesium (MgO) 0.20-0.33 0.20-0.40 0.03-0.32 0.68-1.87 Silica (SiO2) 0.06-0.71 0.07-0.33 0.01-0.07 0.05-1.41 Phosphate (P2 O4) 0.01-0.40 0.02-0.08 0.01-0.02 0.07-0.14 Iron (Fe2O3) 0.06-0.14 0.01-0.03 0.007-0.01 0.04-0.07 Sulfated ash 3.6-4.4 2.8-3.9 3.1-6.5 12.0-19.0 Conductivity ash 3.4-4.4 3.7-4.5 3.9-4.5 14.2-17.7

Phosphate, silica, and magnesium are partially removed by clarification. However,

Potassium, chlorides sodium and low concentration of sulfate are not removed, and these materials tend to become concentrated with processing. When molasses has high concentration of minerals, especially potassium, sucrose retention in molasses in increased, causing losses to the processor. Potassium is the most abundant in the juice (up to 60% of ash).

HOW MONITORING OF WASTEWATER FOR SUGAR IS DONE IN BUSCO

• All wastewater flow to central sewer.

• Continuous collection of hourly samples taken for 24 hours daily was done during milling and refining operations.

• The composite hourly sample was taken using an automatic sampling pump, which delivers sample every 15 seconds and the receiving container emptied before the next sample is collected.

• Laboratory analysis of wastewater sample is done as soon as possible, reporting any abnormality in the test to the shift assistant superintendent or the lab supervisors for counterchecking the result.

• Arsenomolybdate test is the method use in determination for traces of sugar in wastewater. (Source: p. 746 Chen-Chou Cane Sugar Handbook 12th ed.)

• K-tracer in monitoring sources of entrainment loss in the evaporator or vacuum pan condensers.

2 4 2

• Pre-determination of sucrose to potassium ratio.

• Sucrose to Potassium ratio was pre-determined by analysis of potassium in clarified juice and the wastewater entering the Wastewater Treatment Plant. Composite samples for the day were taken for analysis using Tetraphenylborate Method by HACH.

Arsenomolybdate Reagent for Spectrophotometric Determination of Trace Sugars (p. 810 Chen & Chou)

Dissolve 25 grams of ammonium molybdate (Analytical Reagent) in 450 l of distilled

water. Add 21 l of conc. Sulfuric Acid (AR) and mix well). Then add 3 grams of sodium arsenate (Na HASO 7H O) (AR), dissolved in 25 ml of distilled water. Mix and heat to 55oC for 25 min. with constant stirring to prevent overheating. Store in a stoppered bottle made of dark glass.

Arsenomolybdate Test (p. 746 12th ed. Chen & Chou)

1. Mix 5 ml of sample with ml of arsenomolybdate reagent.

2. Place the mixture in boiling water for 15 min., then cool for 10 min.

3. The color developed can be quantified with standards or by spectrophotometer.

Note: Dilute samples that may contain high amount of sucrose.

Make a standard graph for spectrophotometric determination with known concentration of pure sucrose in ppm or mg/L Quantify your result in mg/L sucrose.

• Volume of influent is measured using suppress rectangular weir computed in cubic meter/ day

• Approximate equivalent: -Lkg bags of refined sugar can be estimated using the data gathered.

SUCROSE/POTASSIUM RATIO IS: (p.748 Cane Sugar Handbook 12th ed., Chen & Chou) 85:1- 100:1 FOR SYRUP 31:1 FOR A-MOL 14:1 FOR B-MOL

DATA Clarified Juice Brix Calculation Pol K, Flow Kg/hr Apparent Purity K to sugar ratio, Kg K/kg sugar K, mg/L

Main Drain

Sugar mg/L K, mg/L Flow, m3/hr Sugar Loss, Kg/hr

Calculated Sugar Loss (via K) If syrup, Juice Kg/hr A mol, Kg/hr B mol, Kg/hr C mol, Kg/hr

The figures given in the table and graph are as percentage of sugar in Lkg-bags entering the Wastewater Treatment Plant as determined daily during milling and refining season of crop year 2007 to 2010, accounted as undetermined from both the Raw House and the Refinery Process.

MARCH 2010 POTASSIUM FLOW kg/hr

The next table showed an example on how monitoring of sugar from condenser water

coming from the spray pond was monitored using Potassium Tracer. The most abundant mineral constituent in sugarcane juices, syrup and molasses is potassium as K2O, having a % solid concentration of 0.4-2.0,0.3-1.0,2.3-6.5 respectively.

Calculated Sugar Loss (via K)

Based on computed sugar loss kg/hour the sources of entrainment can be traced if it came from syrup/ juice, A mol, B mol, or C mol. The reduction of sugar loss to sewer is an in-plant control that can be minimized in factory operation. Insignificant in quantities but it’s a heavy money loss for the company and lessen our burden in treating our wastewater.

SUMMARY AND CONCLUSION

Quantifying sugar losses in wastewater by Potassium Tracer can serve as a guide to signal the Raw and Refinery Process of the possible sources of entrainment loss, thereby maximizing the amount of sugar free condensate as a source of boiler feed water.

RECOMMENDATION

Emphasis on waste minimization by controlling sugar contamination in wastewater is needed in Process workforce. Prevention of entrainment, recycling and reuse of wastewater for cooling equipments, are keys to environmental protection in sugar industry.