General information

An international Workshop on rubber factory waste water treatment and disposal was funded by the International Rubber Research and Development Board (IRRDB). It was organized by the Rubber Research Institute of Sri Lanka (RRISL) from held from 8th to13th March 1999.

In 1971 the Rubber Research Institute of Malaysia (RRIM) reported a mthod for the treatment of rubber factory waste/effluent performed by biological processes. Recent technological development by the RRISL since 1990 has produced a cost effective biological treatment process. This is based upon high rate anaerobic digestion coupled with aerobic digestion for the treatment of rubber processing effluent. A new medium, based on cocnut fibre, was designed and manufactured by the RRISL especially for rubber waste treatment, but it can also be used for treating any biodegradable liquid waste.

The workshop was an appropriate activity for sharing information amongst participants and should lead to improvements in the treatment of rubber effluents in other countries.

Participants

The workshop was attended by 6 persons (researchers/experts) from

RRI Thailand (Mr. Pichet Chaipanich - soil scientist)

RRI Indonesia (Mr. Didin Suwardin - precessing technologist)

RRI Malaysia Mr. Devaraj Veerany - chemist, and

Mr. M. Magathenan - processing technologist)

RRI Vietnam (Mr. Nguyen Ngoc Bich -environmental scientist Mr. Truong Minh Trung).

Programme

Basically, the programme for the Workshop could be divided into three activities: lectures, test trials in the laboratory and pilot plant, and field trips (Table 1).

1. Lecture activities were conducted by

(a) Dr. W.M.G. Seneviratne (Principals of wastewater treatment with special reference to rubber processing effluents and methodologies adapted for the treatment of rubber wastes), and

(b) Mr. M.T. Warnakulata (A new medium for biological wastewater treatment: practical applicability and usefulness).

2. Activities in the laboratory and pilot plant were explained and followed up by practical activities on effluent quality parameter testing. Participants were involved in individual testing with the assistance of RRISL staff.

3. Field trips included visits to 7 rubber factories (crepe, RSS, centrifuged latex) and treatment plants in Ellakanda, Hanwella, Padukka, Ehehyagoda, Pussella, Kiriporuwa and Raygam, as well as visits to the laboratory and pilot plant of the environmental consultant company Puritas Ltd.

Evaluation

1. Technology on wastewater treatment from rubber factories (crepe, RSS, centrifuged latex and TSR) as implemented by the RRISL, is basically similar to technology developed by the RRIM in 1971. The treatment system includes both anaerobic and aerobic processes with some variation.

The system has been improved by the RRISL since 1990, especially by the implemention of a new medium for the microbiological activity. This medium is made from coconut coir in the form of bio-brush and rubberized coir. In addition, the RRISL has improved the septic system for the anaerobic process. By using these media it is possible to obtain a high efficiency in waste water treatment (shorter retention time and narrower space).

The major thrust within the Workshop was to present the use of coconut fibre as a new medium for the growth of micro-organisms in effluent treatment systems. Packed in reactors (mostly anaerobic ones), this medium provides the micro-organisms with plenty of space to grow. The coconut fibre, is in the form of rubberised coir cuttings, or caterpillar-like objects called "Bio-brushes". These increase the efficiency of effluent treatment reactors.

2. Bio brush technology made of coconut coir can be implemented in Indonesia, Thailand, and Malaysia, because the material is easy to obtain. Moreover, the material can be extended to include waste oil palm fibres.

3. The treatment system can be enhanced by a biogas collecting system for multi-purpose use. This potential energy, however, has not been explored extensively.

4. The implementation of treatment systems is dependent upon the type of effluent and COD rate (Table 2). Generally, the operational cost of the biological treatment system is low to very low, and the investment cost varies according to the kind of treatment and consultant company status. Foreign consultant companies are tend to be more expensive than local companies.

5. This innovative use of the coconut fibre, developed by RRISL through research work since 1988, is cost-effective and achieves a high performance. For instance, an anaerobic digester packed with rubberized coir cuttings produced a COD removal efficiency of about 90% using a hydraulic retention time of 2 days in treating crepe effluent possessing a COD of approximately 4000 mg/l. Mr Nguyen states that this is quite remarkable. As coconut fibre is very cheap and abundant in most Hevea-growing countries, its application in effluent treatment systems is widely available. This is the most important outcome of the Workshop.

6. There is still a problem with nitrogen removal, for anaerobic digestion generally does not remove much of the nitrogen. However, the anaerobic digester packed with coconut fibre did perform well on a commercial scale, i.e., it was highly capable in removing organic pollutants.

7. The Workshop was an appropriate activity for sharing information amongst participants and enhancing the participants' capabilities.

Acknowledgments

The participants acknowledged the help which they had received from Dr. Tillekeratne (Director of RRI Sri Lanka), Dr. WMG Seneviratne, Mr. T. Warnakulata and other RRISL staff, as well as their own Directors.

Table 1. The programme of the Workshop on rubber factory wastewater treatment and disposal 8-13th March 1999, RRISL

Table 2. Results on visiting the rubber factories and treatment plants (all are equipped with rubber traps)

No	Name Factory	Type effluent	COD Rate (mg/ltr)	Effluent Rate (m3/days)	Treatment system	Performance	cost
							Invesment	Operational
1	RRISL pilot factory	crepe	4000	20	packed anaerobic digester+ aeration tank + clarifier + sand bed filter	excellent	low	low
2	Hanwella	mixed (RSS, CL, crepe, gloves)	2000-4000 NA	50	aerobic (oxidation ditch) + clarifier + sand bed filter	good	medium	low
3	Padukka	crepe	3000-6000 4000	80	anaerobic+ packed aerobicdigester + clarifier + sand bed filter	under construction	low	-
4	Ellakanda	crepe	4000 4000	50	packed anaerobic digester +rotating bio-contactor + clarifier + sand bed filter (RBC)	having problems	high	?
5	Kiriporuwa	crepe	4000	50	packed an`aerobic digester + aeration tank + clarifier + sand bed filter	good	medium	low
6	Eheliyagoda	crepe	2000-4000 4000	20	anaerobic digester +aerobic (aerated lagoon) + clarifier + sand bed filter	fair	high	low
7	Pussella	crepe	3000-6000 4000	80	packed anaerobic digester +aeration tank + clarifier + sand bed filter	good	medium	low
8	Kayigam	crepe	2000-4000 4000	20	covered anaerobic ditch + wet land (CAD)	fair	very low	very low

Appendix
Effluent analysis methods

1. Determination of Chemical Oxygen Demand (COD)

The Chemical Oxygen Demand (COD) determination provides a measure of the oxygen equivalent to that portion of the organic matter in a sample that is susceptible to oxidation by a strong chemical oxidant. The dichromate reflux method has been selected for the COD determination because it has advantages over other oxidants in oxidizability, applicability to a wide variety of samples and ease of manipulation.

1. Apparatus

• Reflux apparatus.
• Hot plate having sufficient power to ensure adequate boiling of the contents of the refluxing flask.

2. Reagents

• Standard potassium dichromate solution, M/24: Dissolve 12.25g of K₂Cr₂O₇, primary standard grade, previously dried at 103 ⁰C for 2 hours, in distilled water and dilute to 1000 ml.
• Sulphuric acid H₂SO₄ conc.
• Standard ferrous ammonium sulphate titrant 0.1 M (FAS): Dissolve 39 g Fe(NH₄)₂(SO₄)₂.6H₂0 in distilled water. Add 20 ml conc. H₂SO₄, cool and dilute to 1000 ml. This solution must be standardized against the standard potassium dichromate solution.

• Standardization: Dilute 10 ml standard potassium dichromate solution to about 100 ml. Add 30 ml conc. H₂SO₄ and allow to cool. Titrate with the ferrous ammonium sulphate titrant, using 2 drops of ferroin indicator.

Molarity of FAS solution = vol. K₂Cr₂O₇ solution titrated, (ml x 0.25)

vol. of FAS used in titration, (ml)

• Ferroin indicator solution: dissolve 1.485 g 1,10-phenanthroline monohydrate together with 695 mg FeSO₄.7H₂0 in distilled water and dilute to 100 ml.
• Silver nitrate.
• Mercuric sulphate, analytical-grade crystals (HgSO₄).

3. Procedure

3.1. Determination of the amount of chloride present before doing COD test.

• Shaking sample before testing and take 10 ml sample, add 5 drops of potassium chromate solution 5% w/v K₂CrO₄ (yellow) into conical flask of 125 ml.
• Add silver nitrate drop by drop until the solution becomes brown.
• If after 1 drop of silver nitrate, the solution already changes its colour, that means chloride is not present.
• Weigh the correct amount of mercuric sulphate into COD flask if chloride is present: 1 ml AgNO₃ = 1 mg Cl

Use 0.4 g HgSO₄ to complex 40 mg chloride ion, when 40 ml of sample is used. If more chloride is present, add more HgSO₄ to maintain a HgSO₄: Cl ratio of 10:1.

Preparation of diluted sample

3.2. Determination of COD of sample

• Pour 20 ml sample or a suitably diluted sample (see dilution table) and mix.
• Then add 10 ml standard potassium dichromate solution and several glass beads.
• Slowly add 30 ml conc. H₂SO₄, mixing thoroughly by swirling while adding the acid.
• Attach the condenser to the flask and reflux the solution for two hours.
• Cool and then wash down the condenser with distilled water, cool to room temperature.
• Titrate the excess dichromate with standard ferrous ammonium sulphate, using ferroin indicator. Generally, use 3 drops of indicator. Take as the end point, the sharp colour change from blue green to reddish brown.
• With each batch of determination, carry out a control blank following exactly the same procedure using distilled water instead of the sample.

4. Calculation

COD (mg/l) = (bl.tiration value)-(sp .titration value)xO.25x 1 Ox 8000

sample volume x blank titration value

2. Determination of Biochemical Oxygen Demand (BOD)

The Biochemical Oxygen Demand (BOD) determination is an empirical test in which standardized laboratory procedures are used to determine the relative oxygen requirements of wastewaters, effluents and polluted waters. The test measures the oxygen utilized during a specified incubation period.

The principle of the method is simple, the dissolved oxygen is determined before and after the incubation period. The difference gives the BOD of the sample. The incubation period adopted is 3 days at 30 ⁰C.

1. Apparatus

• 300 ml Wheaton incubation bottles.
• Air incubator at 20 ⁰C (BOD₅) or 30 ⁰C (BOD₃).
• DO meter

2. Reagents

• Phosphate buffer solution: prepare by dissolving 8.5 g KH₂PO₄, 21.75 g K₂HPO₄, 33.4 g Na₂HPO₄.7H₂O and 1.7g NH₄Cl in about 500 ml of distilled water and dilute to 1 litre. The solution must be discarded if biological growth exists in the bottles.
• Magnesium sulphate solution: prepare by dissolving 22.5 g MgSO₄.7H₂O in 1 litre distilled water.
• Calcium chloride solution: dissolve 27.5 g CaCl₂ in distilled water and dilute to 1 litre.
• Ferric chloride solution: dissolve 0.25g FeCl₃.6H₂O in distilled water and dilute to 1 litre.
• Acid and alkali solution 1 N:
• Acid 1 N: dilute 28 ml conc. H₂SO₄ to 1 litre with distilled water.
• Alkali 1 N: dissolve 40g NaOH in distilled water, dilute to 1 litre.
• Sodium sulphite solution: dissolve 1 .575g Na₂SO₃ in 1000 ml distilled water.
• Nitrification inhibitor, 2-chloro-6-(trichloro methyl) pyridine.
• Glucose-glutamic acid solution: dry reagent-grade glucose and reagent-grade glutamic acid at 103 ⁰C for 1 hour. Add 150 mg glucose and 150 mg glutamic acid to distilled water and dilute to 1 litre.
• Ammonium chloride solution: dissolve 1.15 g NH₄Cl in about 500 ml distilled water, adjust pH to 7.2 with NaOH solution, and dilute to 1 litre.

3. Procedure

a-Preparation of dilution water:

Add 1 ml each of phosphate buffer, magnesium sulphate, calcium chloride, and ferric chloride solutions for each litre of distilled water that should be at 30 ⁰C (BOD₃).

b-Seeding

Some samples do not contain a sufficient micro-organism concentration. For such waste, seed the dilution water by adding a seeding material, usually from domestic sewage after settling at room temperature, for at least 1 hour but no longer than 36 hours.

c-Sample pre-treatment

• Sample containing acidity or alkalinity: neutralise to pH 6.5-7.5 with 1 N NaOH or 1 N H₂SO₄ respectively.
• Sample containing residual chlorine compounds: It should be destroyed by adding Na₂SO₃ solution. Determine required volume of Na₂SO₃ solution on a 100 to 1000 ml portion of neutralized sample by adding 10 ml of 1+1 acetic acid or 1+50 H₂SO₄, 10 ml potassium iodide (KI) solution (l0g/l00ml) per l000ml portion, and titrating with 0.025N Na₂SO₃ solution to the starch-iodine end point for residual.

d-Dilution technique

Dilutions that result in a residual DO of at least 1 mg/l and a DO uptake of at least 2mg/l after 5 days or 3 days incubation produce the most reliable results. Dilutions are made directly in BOD bottles. Using a wide tip pipette add the desired sample volume to individual BOD bottles (and seed material if necessary) and fill with dilution water.

e-Before incubation determine DO of the sample.

f-Incubate for 3 days at 30 ⁰C (BOD₃) and determine the DO at the end of 3 days.

g-Dilution water blank

With each batch of sample incubate a bottle of unseeded dilution water. The DO uptake should not be more than 0.2 mg/l.

h-Seed control

If dilution water is seeded, determine the seed DO by marking a series of seed dilutions such that the largest quantity results in at least 50% DO depletion in 3 days.

i-Glucose-glutamic acid check

Use a mixture of 150 mg glucosell and 150 mg glutamic acid/l as a "standard" check solution.

4. Determine the 3 days 30 ⁰C (BOD₃)

Calculation:

• When dilution water is not seeded:

BOD₃ mg/l = [(DO first day-DO final day)-(blank difference)]x300 mg/l

sample volume taken (mll)

• When dilution water is seeded:

BOD₃ mg/l = [(D₁-D₂)-(B₁-B₂)] x f

P

where:

D₁ = DO of sample immediately after preparation,mg/l

D₂ = DO of sample after 3 days incubation ,mg/l

P = Decimal volumetric fraction of sample used

B₁ = DO of seed control before incubation, mg/l

B₂ = DO of seed control after incubation, mg/l

f = volume of seed in diluted sample

volume of seed in seed control

3. Determination of Total Kjeldahl Nitrogen

This is to measure the total ammoniacal nitrogen and organic nitrogen. The total nitrogen content of rubber effluent is normally determined by the macro method. Basically the method involves the conversion of originally bound nitrogen in the trinegative state to ammonium hydrogen sulphate by the action of sulphuric acid in the presence of catalyst. Ammonia evolved is then determined by titration after distillation.

1. Apparatus

• Electrical heating.
• Distillation apparatus.

2. Reagents

• Sulphuric acid, conc. (H₂SO₄) AR
• Catalyst: prepare by thoroughly mix 250 g of anhydrous sodium sulphate, 4 g of selenium powder and 4 g of copper sulphate.
• Sodium hydroxide 6 N (NaOH): prepare by dissolving 250 g NaOH in one litre ammonia-free distilled water.
• Absorbent solution plain boric acid: prepare by dissolving 20 g boric acid H₃BO₃ in ammonia-free distilled water and dilute to one litre.
• Screened methyl red indicator: dissolve 0.1 g methyl red and 0.05 g methylene blue in 100 ml of ethyl alcohol.
• Phenolphthalein indicator.
• Sulphuric acid 0.01 M.
• Glass beads or boiling chips.

3. Procedure

• Mix together in a 300-500 ml Kjeldahl flask, a suitable amount of sample and one scoop of approximately 1g of catalyst and a few boiling chips.
• Determine the volume size from the table below:

• Add 10 ml of sulphuric acid, concentrated, and heat the flask briskly until the mixture turns green and sulphur trioxide fumes are generated.
• Continue heating gently for a further half-hour and then allow the flask to cool.
• Wash the Kjeldahl flask with an additional 50 ml of distilled water and add about 250 ml of distilled water and transfer quantitatively the contents to a distillation flask.
• Add a drop of phenolphthalein indicator and sufficient sodium hydroxide 6 M (usually about 50 ml) to ensure that the mixture is alkaline. Fit the splash head to the flask.
• Pour 20 ml of absorbent solution into the 500 ml conical receiving flask and add 2 to 3 drops of screened methyl red indicator.
• Boil the contents of the distillation flask briskly until more than 200 ml of distillate has been collected in the receiver.
• Immediately titrate the distillate with standard sulphuric acid 0.01 M by taking the end-point at the appearance of a permanent purple blue colour.
• With each batch of determination, carry out a control blank determination following exactly the same procedure using distilled water instead of sample.

4. Calculation

Total Kjeldahl nitrogen, mg/l = (A-B) x C x 28000

S

where A = ml of standard 0.O1M H₂SO₄ solution used in titrating sample;

B = ml of standard 0.01M H₂SO₄ solution used in titrating blank;

C = Actual molarity of 0.01M sulphuric acid solution;

S = ml of sample digested.

4. Determination of Ammoniacal Nitrogen

The ammoniacal nitrogen includes the total sum of free and fixed ammonia. The fixed ammonia is derived from the reaction of ammonia and acid to form corresponding ammonium salt. The ammoniacal nitrogen content is usually determined by a distillation and titration method.

1. Apparatus

• Electrical heating
• Distillation apparatus

2. Reagents

• Borate buffer solution: prepare by adding 88 ml of 0.1 M NaOH solution to 500 ml of 0.025 M sodium tetraborate Na₂B₄O₇ solution (5g Na₂B₄O₇ or 9.Sg Na₂B₄O₇. 10H₂O).
• Sodium hydroxide NaOH 6M: prepare by dissolving 240 g NaOH in 1 litre ammonia-free distilled water.
• Absorbent solution, plain boric acid: dissolve 20g H₃B0₃ in ammonia-free distilled water and make up to 1 litre.
• Screened methyl red indicator: dissolve 0.1 g methyl red and 0.05 g methylene blue in 100 ml ethyl alcohol.
• Phenolphthalein indicator.
• Sulphuric acid 0.01 m.
• Glass beads or boiling chips.

3. Procedure

• Measure a suitable amount of sample (refer to table) into the distillation flask and add distilled water to give a total volume of about 300 ml.
• Add 20 ml of borate buffer and adjust pH to 9.5 with 6M NaOH solution, using phenolphthalein indicator.
• Add a few boiling chips or glass beads and fit the splash head to the flask.

• Pour 20 ml of absorbent solution into the 500 ml conical receiving flask and add 2 drops of screened methyl red indicator.
• Boil the content of the distillation flask briskly until about 200 ml of distillate has been collected in the receiver.
• Immediately titrate the distillate with the standard sulphuric acid 0.01M, taking the end point at the appearance of a permanent purple blue colour.
• With each batch of determination carry out a control blank determination following exactly the same procedure except that water is added instead of the sample.

4. Calculation

Ammoniacal nitrogen, mg/l = (A-B) x C x 28000

S

where A = ml of standard 0.01M H₂SO₄ solution used in titrating sample;

B = ml of standard 0.01M H₂SO₄ solution used in titrating blank;

C = Actual molarity of 0.01M sulphuric acid solution;

S = ml of sample used.

5. Determination of Total Solids

Solids analyses are important in control of biological and physical wastewater treatment processes, solids may affect water or effluent quality adversely in a number of ways. Highly mineralized waters also are unsuitable for many industrial applications.

1. Apparatus

• Evaporating dish: dish of 100 ml capacity made of porcelain, 90 mm diameter.
• Drying oven for operation at 103 to 105 ⁰C.
• Desiccator.
• Analytical balance, capable of weighing to 0.1 mg.

2. Procedure

• Heat clean dish to 103 to 105 ⁰C for one hour.
• Store and cool dish in desecrator and weigh before use.
• Pipette a suitable, measured volume of well-mixed sample onto a preweighed dish.
• Evaporate to dryness in a drying oven.
• When evaporating in a drying oven, lower temperature to approximately 2 ⁰C below boiling to prevent splattering.
• Dry evaporated sample for at least one hour.
• Repeat the drying cycle until a constant weight is obtained or until the weight change is less than 0.5 mg.

3. Calculation

mg/l Total Solids = (A-B) x 10⁶

S (ml)

where A = weight of dish + residue (g)

B = weight of dish (g)

S = volume of sample evaporated, ml.

6. Determination of Total Suspended Solids (TSS)

Solids refer to matter suspended or dissolved in water or wastewater. Waters with high dissolved solids generally are of inferior palatability and may induce an unfavourable physiological reaction in the transient consumer. For these reasons, a limit of 500 mg dissolved solids per litre is desirable for drinking waters.

Total solids is the material residue left in the vessel after evaporation of a sample and its subsequent drying in an oven at a defined temperature. Total solids includes "total suspended solids", the portion retained by a filter, and "total dissolved solids", the portion that passes through the filter.

1. Apparatus

• Glass fibre discs, Whatman GF/B grade or equivalent, 25 mm diameter.
• Filtration apparatus: Filter holder; Gooch crucible adapter, Gooch crucible, 30 ml capacity.
• Suction flask 500-1000 ml.
• Dryingoven 105±1⁰C.
• Desiccator.
• Analytical balance, capable of weighing to 0.1 mg.

2. Procedure

• Preparation of glass fibre discs: place the disc on the bottom of a suitable Gooch crucible and place Gooch crucible with GF/B filter paper into an oven to dry at 105 ⁰C for one hour, cool and previously weigh before use.
• Apply vacuum and wet filter with a small amount of distilled water to seat it.
• Pipette a suitable, measured volume of well-mixed sample onto the seated filter.
• Wash the filter with three successive 20 ml of distilled water, allowing complete drainage between washings and continue suction until complete drainage.
• Remove the crucible and filter combination from the crucible adapter.
• Dry for at least one hour at 103-105 ⁰C in an oven.
• Cool in a desiccator to balance temperature and weigh.
• Repeat the cycle of drying, cooling, desiccating, and weighing until constant weight is obtained or the weight change is less than 0.5 mg.

3. Calculation

mg/l Total Suspended Solids = (A-B) x 10⁶

S (ml)

where A = weight of filter + residue (g)

B = weight of filter (g)

S = volume of sample filtered, ml.

7. Determination of pH Value

Determination of pH is required in order to know whether the effluent is acidic or alkaline. Normally the effluent discharged from rubber factories is acidic due to the use of acid to coagulate the latex. The pH value of the effluent is normally determined by a pH meter.

1. Apparatus

• pH meter with a glass electrode, pH 0.0 to 14.0;
• Beaker: polyethylene;
• Stirrer: TFE-coated stirring bar.

Reagents

Standard buffer solutions of known pH: 4.00; 7.00; 9.00.

2. Procedure

2.1. Instrument calibration:

• Follow the manufacturer's instruction for pH meter;
• Standardize the instrument against at least two pH standard solution.

2.2. Measuring the pH

• Before measuring the pH value, rinse the electrode with distilled water and wipe dry with a clean tissue paper.
• Shaking sample and pour into the beaker. Immerse the electrode into water sample and stir gently to ensure homogeneity and to minimize carbon dioxide entrainment until a constant reading.
• Read and record pH value of the sample to the nearest 0.1 unit.