Central Environmental A u t h o r i t y Par isara M a w a t h a

M a l i g a w a t t a New T o w n Colombo 10 SKI 1.ANKA

T e l e p h o n e No: 449455/6 . 437487 /8 /9 Fax N o : 01-446749

ISBN 955-9012-02-9 Rs 100.00

PPtMTEDBY UNTTED MERCHANTS LTD COLOMBO tS

GOVERNMENT OF THE DEMOCRATIC SOCIALIST REPUBLIC OF SRJ LANKA

I N D U S T R I A L P O L L U T I O N C O N T R O L G U I D E L I N E S

No. 3 — Desiccated Coconut Industry

INDUSTRIAL POLLUTION CONTROL GUIDELINES

No 3 Desiccated Coconut Industry

CEA Library

" " 0 4 4 2 5

Prepared by the Central Environmental Authority With Technical Assistance from The Government of the Netherlands

1992/93

First edition 1992

Published by the Central Environmental Authority Parisara Mawatha Maligawatta New Town Colombo 10 SRI LANKA

Telephone No:449455/6, 437487/8/9, 439073/4/5/6 Fax No: 01-446749

This document may be reproduced in full or in part with due acknowledgement to the Central Environmental Authority

ISBN 955-9012-02-9

Front Cover Design & concept by W A D D Wijesooriya Artwork by Somasiri Herath

024/waddw/guide3

PREFACE

The Government of Sri Lanka is promoting rapid industrialization in order to create better employment opportunities for the growing work force of the country, and to increase the income level of the people. At the same time the Government is conscious of the fact that some of the existing industries significantly contribute to the deterioration of the quality of the environment in the country, especially in the urbanised and industrialized areas. Ill-planned industrialization will no doubt accelerate the process of environmental degradation.

The Government has, therefore, introduced environmental legislation to enhance environmental protection and pollution control. The Central Environmental Authority (CEA) is the lead agency in the implementation and enforcement of the environmental legislation. It has initiated various programmes for the protection of the environment, with special attention on industrial pollution control.

The CEA has requested technical and financial assistance from the Government of The Netherlands for a number of projects in this field.

As a result technical assistance for a programme which consist of the following projects was provided by the Government of The Netherlands:-

1. Development of environmental quality standards on the basis of designated uses .

2 . Development and updating of emission/discharge standards and pollution control guidelines for selected priority industries

3 . Feasibility studies on pollution control for priority industries or industrial sectors

4 . Study tour to The Netherlands for Sri Lankan officers involved in compliance procedures in the Environmental Protection Licensing Scheme (enforcement)

Under project No 2 above, industrial pollution control guidelines, were prepared for the following eight(8) industrial sectors, considered as major polluters in Sri Lanka:-

1. Natural Rubber Industry 2 . Concentrated Latex Industry 3 . Desiccated Coconut Industry 4 . Leather Industry 5. Dairy Industry 6. Textile Processing Industry 7. Pesticide Formulating Industry 8. Metal Finishing Industry

The main objective of the preparation of these guidelines w a s to assist the Central Environmental Authority in industrial pollution control with special reference to the introduction of the Environmental Protection Licensing Scheme .

In the preparation of these guidelines attention w a s focused on the generation of liquid, gaseous and solid was t e s and their impacts on the environment. In the process aspec t s of industrial counselling, including in-plant measures to prevent and reduce w a s t e generation and measures to improve occupational safety and health were also considered. Alternative methods were discussed for end-of-pipe t reatment of liquid . gaseous and solid w a s t e s .

Existing was t ewa te r discharge quality s tandards were considered and intermediate

s tandards ( with respect to the phased installation of t rea tment sys tems) were

proposed in t he se guidelines.

The guidelines were mainly prepared on the basis of data available on industrial

pollution and its abatement in sri Lanka, from studies and reviews carried out in the

past and from missions to Sri Lanka specifically carried out for preparation of t he se

guidelines.

The project w a s u . ^ c t e d by Mr K G D Bandaratilake. Director of the Environmental Protection Division of the CEA, and coordinated by Mr W A D D Wijesooriya, Senior Environmental Scientist of the CEA. The CEA project team consisted of Mr C K Amaratunga and Mr S Seneviratne, Environmental Officers.

Technical ass is tance w a s given by a team of BKH Consulting Engineers, Comprises Dr I van der Putte (team leader), Mr J G Bruins and M r H J F Creemers.

This document contains pollution control guidelines for Desiccated Coconut

Industry.

G K Amaratunga Chairman Central Environmental Authority

Contents Page

1. INTRODUCTION 1

2. PRODUCTION OF DESICCATED COCONUT 2

2.1 Production data 2 2.2 Production process 2

3. WASTE PRODUCTION AND ENVIRONMENTAL IMPACTS 4

3.1 Waste production 4 3.2 Air pollution and solid waste 4 3.3 Environmental impacts 4

4. INDUSTRIAL COUNSELLING 5

4.1 Introduction 5 4.2 In-plant pollution control 5 4.3 Improvement of occupational safety and health 6

5. POLLUTION ABATEMENT METHODS 7

5.1 Introduction 7 5.2 Wastewater treatment alternatives 7 5.3 Wastewater treatment system choice 13 5.4 Air pollution control 14

6. DISCHARGE AND EMISSION STANDARDS 15

6.1 Wastewater discharge quality standards 15 6.2 Emission standards 15

7. REFERENCES 16

Annex I Industrial Emission Standards in Thailand

INTRODUCTION

Coconut products are the second agricultural export product ol Sri Lanka after tea. Desiccated coconut accounts for 40% of the total export revenues from coconut products. Sri Lanka is the second largest producer of desiccated coconut (after the Philippines) and the production is still growing rapidly.

The production of desiccated coconut (DC) generates wastewater with high concentrations of biodegradable organic compounds, including carbohydrates, oil and greases. The wastewater of the Sri Lankan DC mills is not treated. Most factories are located in rural areas and discharge their wastewater into nearby streams. These discharges may result in harm to aquatic life and emission of odours due to putrefaction of organic compounds. Resulting eutrophication of surface waters may also adversely affect the quality of surface water for drinking and bathing purposes.

This document provides guidelines for industrial pollution control including industrial counselling and wastewater treatment for the desiccated coconut industry. These guidelines will provide a pollution control programme, which could enable a stage-wise compliance with interim and ultimate quality standards for wastewater discharge.

2. THE PRODUCTION OF DESICCATED COCONUT

2.1 Production data

The Sri Lankan coconut processing industries produce 50,000 tonnes of desiccated coconut (DC) per year, accounting for almost 40% of the worldwide production of DC. The production is still increasing. Currently the installed production capacity amounts to 75,000 DC per annum. There is no local market for DC in Sri Lanka; all of it is exported.

Islandwide, approximately 400,000 hectares (6% of the total surface area) are covered with coconut plantations, yielding annually about 2,500 million coconuts. These plantations as well as the desiccated coconut mills are mainly located in the triangle of the three cities of Colombo, Kurunegala and Puttalam.

Presently 53 DC mills are in operation, of which 5 mills are large scale factories, processing over 100,000 coconuts/day. The remaining 48 mills are small and medium-scale, processing less than 50,000 coconuts/day. All DC mills are privately-owned.

2.2 Production process

Desiccated coconut is manufactured from the white inner layer of the coconut (the kernel). Seasoned mature coconuts are supplied to the factory in lorries after the coir fibres have been removed.

The coconuts are cut open manually, producing coconut shells as a by-product. The shells are either sold to manufacturers of charcoal and activated carbon, or they are burned in the factory furnaces.

The second layer or the inner shell, being the transition of the brown coconut shell to the white kernel, is also removed manually. This results in a second by-product: copra. Copra has a very high oil content and is usually sold to oil mills for oil extraction. Occasionally copra is used as animal food.

The remaining kernel is finally cut open into several pieces. The coconut water is released and is the major source of wastewater. The white kernel pieces are subsequently washed with chlorinated water (calcium hypochlorite, 200 mg/l). Washing is another source of wastewater. Then, the coconut pieces are sterilized. Generally sterilizing is carried out by boiling in water for 1 t6 2 minutes. After sterilizing the kernel pieces are cut or ground mechanically into small particles.

In one of the modern large-scale DC mills, the process of sterilizing is carried out differently. Here sterilization takes place after grinding of the kernel into small particles. The particles are not boiled in water, but treated with steam for 1 or 2 minutes in a continuous process. This type of sterilizing with steam generates less wastewater than sterilization in boiling water.

After sterilization the fine particles are dried at 90-95° C in order to reduce the moisture content from 55% to 3 - 3.5%. Heat is generally provided by burning firewood and coconut shells.

2

Finally, a mechanical shifter screens the desiccated coconut into fractions of fine, medium and large size particles. The largest fraction is re-cut. Fine and medium size particles are packed separately in bags containing 50 kg.

3

3. WASTE PRODUCTION AND ENVIRONMENTAL IMPACTS

3.1 Wastewater production

The'total water use of a traditional DC mill processing an average of 50,000 coconuts per day, amounts to 40,000 - 45,000 l/d. The factory wastewater consists of 3 different wastewater flows:

The wastewater production of an average size factory, processing 50,000 coconuts, amounts to about 50 m 3/day. The composition of the wastewater is mainly determined by the coconut water, which has high concentrations of organics and oil (2%). The combined wastewater generally has high concentrations of oil, grease and dissolved solids. It has the following average characteristics:

pH 4.0 - 5.5 BOD 1000 - 5000 mg/l COD 4000 - 8000 mg/l Oil 4000 mg/l

3.2 Air pollution and solid waste

Air pollution is caused by furnaces, which are mostly fuelled by firewood and coconut shells. When wet coconut shells, in particular, are burned, black smoke, fly ash and volatiles are generated. No' solid waste is generated in desiccated coconut mills, since all by-products are utilized or further processed.

3.3 Environmental impacts

Most DC-factories are located in rural areas. The wastewater from DC mills is generally discharged without treatment into nearby streams, paddy fields or uncultivated land. These discharges may result in low dissolved oxygen concentrations in the stream or river and in emission ot bad odours caused by anaerobic degradation of organic substances.

The presence of oily substances in the discharged wastewater, in combination with bad odours, makes the surface water unfit for drinking and bathing purposes. The discharge of desiccated coconut wastewater into paddy fields may cause crop damages due to the low pH of the wastewater.

Emissions of black smoke and flue gases from the boilers may cause nuisance to neighbouring residents.

- sterilization water (water boiling process) - washing water (chlorinated) - coconut water (200 ml x 50,000)

2,700 l/day 40,000 l/day 10,000 l/day

52,700 l/day

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4. INDUSTRIAL COUNSELLING

4.1 Introduction The industrial counselling procedures are directed towards the introduction of environmentally sound technology ('clean technology"). Clean technologies contribute to more efficient production methods by saving energy and raw materials and reducing emissions to air, water and soil. They include good housekeeping measures, modification of production processes and raw materials use, as well as recycling of waste and process waters.

Industrial counselling aims at environmentally sustainable industrial development by promoting a combination of in-plant pollution control and end-of-pipe treatment in order to protect the environment and to optimize the conservation of energy and raw materials.

Additional advantages of the application of cleaner production processes are the reduction of safety hazards and the improvement of occupational health. Therefore, initial investments aimed at pollution control become more cost effective.

In this chapter in-plant pollution control measures and methods to improve occupational safety and health are proposed.

4.2 In-plant pollution control

The wastewater production from sterilizing and washing operations could be reduced by good housekeeping methods and by process integrated measures. However, these measures will not affect the waste load discharged, since waste load is directly related to the number of coconuts processed.

The waste load of the discharged coconut water can be reduced significantly by recovering the oil from it. Coconut water has an oil content of around 2%. Through gravity settling followed by skimming most of the oil can be separated from the coconut water.

The skim oil has an economic value as raw material for small scale soap factories, after the water has been boiled out. In an average factory (50,000 coconuts/day) a recovery of about 200 I of oil per day is possible.

The wastewater flow can be reduced by 20% by sterilizing with steam instead of by boiling in water. Usually the kernel pieces are sterilized by boiling them in water for 1 Vfe minute, prior to grinding and drying. Steam sterilizing, however, is performed after grinding of the kernel. In this continuous process the coconut powder is led through an enclosed steam chamber with a residence time of 1 vi> minute before drying in the drying chamber.

The required capacity of wastewater treatment facilities can be reduced by separate treatment of strongly polluted coconut water separately from the weakly polluted washing and sterilizing wastewater.

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4.3 Improvement of occupational safety and health

Occupational safety and health aspects concern physical, chemical, biological and mental hazards and stresses present in the working environment. The improvement of occupational safety and health aims at the protection of workers at the workplace and its immediate environment against hazards such as heat, dust, noise, vibration, toxic chemicals, airborne pollutants, mechanical hazards, explosions and radiation. It also includes the adaptation of installations and processes to the physical and mental capacity of the workers.

Besides hypochlorite no other chemicals are used in production of desiccated coconut. However, unintended situations may occur in the repetitive mechanical operations with a short cycle, such as cutting of the coconut shell and cutting of the kernel. In cutting operations the hands and the eyes should therefore be protected. In-plant pollution control as described in Section 4.2 may contribute in several ways to improvement of occupational safety and working conditions.

5. POLLUTION ABATEMENT METHODS

5.1 Introduction

In the production processes-no solid waste is generated, since all by-products are recovered and reused. Therefore solid waste disposal is not further discussed in the guidelines.

Air pollution is caused by firewood fuelled furnaces which provide heat for- the drying process. Some air pollution control measures are discussed in Section 5.4.

In most DC mills the wastewaters are combined into one flow and subsequently discharged directly into the nearest stream. Due to the adverse impacts on the water quality by the direct discharge of DC mil] wastewater, and because of the enforcement of industrial wastewater discharge standards by the Sri Lankan Government, the DC mills will be forced to install wastewater treatment facilities in the future.

A number of alternative wastewater treatment systems, which can be installed in stages, is described in the following section (5.2).

Effluent quality standards, related to the installation of wastewater treatment facilities in stages, are proposed in Chapter 6.

5.2 Wastewater treatment alternatives

5.2.1 Pre-treatment of coconut water

The coconut water is treated separately from the other wastewater flows resulting from washing and sterilization. The major reason for separate treatment of the coconut water is its relatively high oil content. The oil can be recovered and utilized for the manufacture, of various oil-based products e.g. soap (see Chapter 4). A second reason for separate treatment is the high chlorine content of the washing water which may adversely affect the anaerobic treatment process.

The coconut oil is conveyed directly into an oil trap/sedimentation tank with a retention time of approximately 3 hours. Oil is skimmed off at the surface of the tank by means of a number of baffles in the tank. Suspended solids settle at the bottom of the tank and are removed regularly by means of an outlet. The solids are conveyed to a drying bed or transported directly to the coconut plantations where they are dumped in a controlled manner.

The coconut water flow from a DC mill, processing 50,000 coconuts per day, has the following average characteristics:

Daily flow 10 Hourly flow 1 (10 hours production per day) pH C,S COD 40,000 BOD 10,000

m 3 /d m 3 /h

mg/l mg/l

7

V

Oil 2,000 mg/l Suspended solids 750 mg/l Total nitrogen (as N) 225 mg/l

The oil trap/sedimentation tank should have the following dimensions:

Tank volume 3 m 3

Surface area 5 m 2

Wet depth 0.4-1.0 m

The tank should have a V-shaped bottom to enhance sedimentation and removal of suspended solids. It is estimated that the effluent of the oil trap/sedimentation tank has the following composition:

pH 4.8 COD 28,000 mg/l BOD 6,000 mg/l Oil 100 mg/l Total nitrogen 200 mg/l

5.2.2 Anaerobic treatment of coconut water

Coconut water can be treated in an anaerobic reactor e.g. an Upflow Anaerobic Sludge Blanket (UASB) type reactor or in an anaerobic pond.

a) UASB reactor

In the UASB reactor the wastewater flows upwards through a blanket of anaerobic bacteria, which biodegrade part of the organic material into gases such as methane (CH4), carbon dioxide (COJ, ammonia (NHJ and hydrogen sulphide (H2S). The gases are collected in the upper section of the reactor by a gas collector. The optimum temperature for the anaerobic process is 35° C The major advantage of this system is that no energy input is needed under tropical conditions. Other advantages are that the anaerobic system requires little space and that production of excess sludge is minimal because of the slow growth of anaerobic bacteria.

The maximum removal efficiency of BOD by the anaerobic system is about 90%, which is generally not sufficient to meet the required discharge standards. For this reason anaerobic treatment is often considered only as a first stage treatment system. A pond system, an activated sludge system or rotating biological contactors can be applied for further treatment. Anaerobic treatment of DC mill wastewater is not yet applied.

Some parameters for design of an UASB reactor are given in Table 5.1.

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Table 5.1 UASB reactor; design parameters

pH (optimum) 6.7 - 7.3 Temperature (optimum) 35° C (mesophilic digestion) Retention time > 8 h Organics to nutrients ratio COD : N : P = 850 : 5 : 1 Organic loading rate < 15 kg COD/m 3 /d Gas production 0.4 Nm 3/kg COD removed

(75% methane)

Before anaerobic treatment the pH of the effluent of the oil trap/sedimentation tank should be raised to a pH equal to 7 - 8, by addition of hydroxide or lime.

The dimensions of the UASB reactor should be as follows:

Volume 20 m 3

Height 4 m Surface area 5 m J .

The estimated composition of the effluent of the UASB reactor is as follows:

pH 7.5 COD 7,000 mg/l BOD 600 mg/l

b) Anaerobic ponds

If sufficient land is available an anaerobic pond can be applied instead of an anaerobic reactor. In the anaerobic pond the organic matter in the wastewater is biodegraded by anaerobic bacteria into gases, such as methane, hydrogen sulphide, ammonia and carbon dioxide. Solids settle into a sludge layer at the bottom of the pond which has to be removed periodically.

The most important design parameters are (for Sri Lankan conditions, average temperature is 27° C)

organic volume loading rate 300 g BOD/m 3.d depth 2.5-4 m BOD removal efficiency 70-90 %

Anaerobic ponds may cause odours. For this reason these ponds should be located at sufficient distance from residential areas (at least 500 m).

The anaerobic pond should have the following dimensions:

Volume 200 m 3

Depth 4 m Area 50 m a (excluding embankments)

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Treatment efficiency of the anaerobic ponds is significantly improved by using two ponds in series, with recirculation of the effluent of the second pond to the first pond. Biological activity and reduction of odours from the ponds are improved by this measure. It is expected that the effluent of the anaerobic ponds will have the same composition as the effluent of the UASB reactor.

5.2.3 Secondary treatment

After anaerobic treatment the coconut water is mixed with the other wastewaters from washing and sterilizing. No accurate data on the composition of these wastewaters are available, but their concentrations of pollutants are low in comparison with the coconut water. It is estimated that the combined wastewater, after separate anaerobic treatment of the coconut water, has the following characteristics (based on a production of 50,000 coconuts per day):

Wastewater flow 52.7 m 3 / d pH 6.5-7.5 COD 1,000 mg/ l BOD 150 mg/ l Oil 50 mg/ l Suspended solids 80 mg/ l Total nitrogen 30 mg/ l

Direct discharge of the combined wastewater into a river or stream should be avoided, since it may still cause serious water pollution, especially during the dry season. The wastewater could be safely used for irrigation of coconut lands, paddy fields or other crops.

It is also possible to treat the combined wastewater by an aerobic wastewater treatment method, depending on the effluent discharge quality standards. Four alternative wastewater treatment methods are briefly discussed hereafter.

a) Facultative ponds

The combined wastewater can be led into a facultative pond. Organic matter is biodegraded aerobically in the upper layers of the pond. Oxygen for this process is mainly supplied by algae. Some anaerobic biodegradation of settled organic material takes place at the bottom of the facultative pond.

The most important design parameters for facultative ponds are:

organic surface loading rate 330 kg BOD/ha.d deptn 1.2 m BOD removal efficiency 80-90 %

Facultative ponds are usually applied in series of 2 or more ponds. The last pond functions as a polishing or maturation pond, in which micro-organisms die off and settle to the bottom. A design example is given below on the basis of the wastewater characteristics given above.

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Facultative pond

Area Depth Volume

Area Depth Volume

Maturation pond

250 1.2

300

105 1.5

160

m J

m

nr m

.3

Effluent quality

COD BOD

250 25

mg/l mg/l

b) Mechanically aerated ponds

An alternative for the facultative pond is a mechanically aerated pond where oxygen for aerobic biodegradation is supplied by mechanical aerators. There are two types of aerated ponds, the completely mixed aerated pond and the facultative aerated pond.

b.1 In the completely mixed aerated pond the contents are completely mixed, and the whole system is aerobic. The effluent from this pond is led into a sedimentation tank or pond, in which solids settle into a sludge. The most important design parameters for completely mixed aerated ponds are:

- required power input 6 W/m 3 pond volume

A mechanically aerated pond is usually followed by a maturation pond, in which micro-organisms die off and settle. A design example, on the basis of the above wastewater characteristics is as follows:

Completely mixed aerated pond

Required power input for oxygenation and mixing 0.3 kW Volume 50 m 3

Depth 2.5 m

Maturation pond

(see facultative pond)

Effluent quality

BOD removal efficiency depth

80 % 2 - 4 m

COD BOD

300 mg/l 30 mg/l

b.2 In a facultative aerated pond only the top layers are kept aerobic by the mechanical aerators. Suspended solids settle to the bottom of the pond, where anaerobic biodegradation takes place. The most important design parameters are:

- required power input 1.75 W/m 3 pond volume BOD removal efficiency 80-90 %

- depth 2.5-4 m

Facultative aerated ponds are usually also followed by a maturation pond. A design example is given below.

Facultative aerated pond

Required power input 0.3 kW Volume 170 m 3

Depth 2.5 m

Maturation pond

(see facultative ponds)

Effluent quality

COD 200 mg/l BOD 20 mg/l

c) Activated sludge

In the activated sludge system the wastewater is led into an aeration tank, where it is mixed with floes of aerobic micro-organisms (activated sludge). The mixture of activated sludge and wastewater is aerated vigorously.

Organic substances in the wastewater are absorbed by the active micro­organisms, which biodegrade the organic matter, utilizing the breakdown products as a substrate for growth and formation of new cells. As a result the sludge quantity in the aeration tank is increased. Micro-organisms die off in the aeration tank, the dead cells being oxidized into inert material (mineralization).

The mixture is led from the aeration tank into a sedimentation tank where the floes settle into a sludge. Part of this sludge is returned to the aeration tank, in order to maintain a constant concentration of activated sludge in it. The remainder of the sludge (surplus sludge) has to be removed. The surplus sludge is often de-watered in a sludge drying bed to decrease its volume.

Controlled disposal of the wet sludge in plantations is also possible.

High load activated sludge systems with a high loading rate of organic matter per quantity activated sludge (kg BOD per kg sludge solids per day) and low load activated sludge systems are used in wastewater treatment.

The advantages of low load systems in comparison with high load systems are higher reliability, better BOD removal, production of a mineralized sludge and simpler operation. One type of low load activated sludge system is the oxidation ditch system.

The most important design parameters for low load activated sludge systems (oxidation ditch) are:

organic sludge loading rate sludge dry solids content in aeration tank oxygen requirement BOD removal efficiency depth (depends on aerator type)

0.15 kg BOD/kg sludge dry solids

4 kg/m 3

2.5 kg0 2 /kg BOD 95-98 %

1.5-2.5 m

d) Rotating Biological Contactors System

The rotating Biological Contactors (RBC) system consist of a series of biorotors, a biorotor being a central horizontal shaft to which a contact surface has been attached. The biorotor is fitted into the tank, into which the combined wastewater, after pretreatment (including equalization), is led. The submersion depth of the biorotor in the tank is 40% of the biorotor diameter. The biorotor rotates slowly, about 1-2 rotations per minute, and a film of sludge, containing aerobic micro-organisms develops on the contact surface of the biorotor. While rotating in the tank the biorotor lifts up a quantity of wastewater, causing intensive contact between wastewater, micro-organisms and oxygen from the air.

The sludge film absorbs organic matter, which is biodegraded aerobically in the process of substrate utilization by the micro-organisms for growth and formation of new cells. The excess sludge is washed off from the contact surface.

The effluent of the biorotor tanks is led into a sedimentation tank in which the excess sludge settles.

Important design parameters for the RBC system are:

biorotor surface loading rate 10 g BOD/m s.d peripheral rotation speed 12.5 m/min biorotor submersion depth 40 % of diameter BOD removal efficiency 90-95 %

Wastewater treatment system choice

The selection of a wastewater treatment system for a DC mill depends on a number of factors, including size and location of the mill, availability of land, and the characteristics of the receiving water. Costs of wastewater treatment and the availability of skilled personnel are also important factors, influencing the selection of a wastewater treatment system.

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If suitable lands are available near the mill, only anaerobic treatment may be necessary, whereas the combined wastewater may be applied to the surrounding lands, or be used for irrigation.

If the receiving water has a high, perennial, dilution capacity anaerobic treatment may also be sufficient depending on the size of the mill.

In some cases complete wastewater treatment may be required. If sufficient land area is available, the most simple system, consisting of anaerobic, facultative and maturation ponds, should be selected.

If very little land is available, a more complicated and expensive system, for example consisting of UASB and RBC units should be selected.

The sludge generated in the wastewater treatment system can be disposed of in coconut plantations.

Air pollution control -

The environmental and human health effects of air pollution can be limited either by reducing the emission of pollutants or by installing stacks with sufficient height. The emissions from firewood fuelled furnaces mainly consist of particulate matter i.e. black smoke and soot. The particulate matter can be removed by applying cyclones or multiclones to the incinerator.

It is also recommended that stacks with sufficient height are installed in order to promote dispersion and dilution of the pollutants in the air. For small scale industries as a general rule the stack height should be 2Vfc times the neighbouring building height and at least 9 meters. The following relation exists between the emission of particulates (Qp) and the required stack height (H):

H = 74 (Qp) 0 2 7 (H in meters, Qp in tonnes/hr) (Ref. 2)

DISCHARGE AND EMISSION STANDARDS

Wastewater discharge quality standards Virtually no wastewater treatment facilities exist at the DC mills in Sri Lanka. There is also little knowledge and experience regarding the characteristics and treatability of DC mill wastewaters. For these reasons it is proposed that wastewater treatment for the DC mills is introduced in a staged programme, related to the phased enforcement of effluent discharge quality standards. The proposed standards are given in Table 6.1.

The wastewater volume generated by DC mills should not exceed 1.1m 3 per 1,000 coconuts processed.

Table 6.1 Proposed standards for the discharge of DC mills effluents into -inland surface waters; maximum allowable concentrations

Parameter Unit Intermediate Ultimate standard standard (Stage I) (Stage II)

pH - 6 . 5 - 8 6.5 - 8 COD mg/l 850 300 BOD mg/l 150 30 Oil mg/l 50 10 Suspended solids mg/l 80 30 Total N mg/l 30 20

Compliance with the intermediate standards can be achieved by anaerobic treatment (e.g. an UASB-reactor or an anaerobic pond). The ultimate standards can be complied with by introducing a second treatment stage i.e. maturation or facultative ponds (in addition to the anaerobic pond) or by means of the RBC-system (in addition to the UASB-reactor).

Emission standards In Sri Lanka no standards have been set for emissions of pollutants into the atmosphere. However, in the desiccated coconut industry considerable emissions of smoke and flue gases are generated from firewood fuelled furnaces. Therefore it is useful to refer to "Industrial Emission Standards" for specified sources, as proposed for Thailand by the Thailand Ministry of Industry. These standards are provided in Annex I (Ref. 2).

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REFERENCES

1. Emission regulations part IV, Central Board for the Prevention and Control of Water Pollution, New Delhi, 1986/87

2. Laws and Standards on pollution control in Thailand, 2nd ed., Environmental Quality Standards Division, Office of the National Environment Board, Thailand, 1989

3. Feasibility report on anaerobic wastewater treatment methods for desiccated coconut factory at Kankaniyamulla. (Serendib Coconut Products Ltd.), Nihal Rajapakse Consulting Engineers, Colombo, December 1990

4. Sri Lanka, Desiccated Coconut, publication from Coconut Development Authority, Colombo, 1990

ANNEX I

STANDARDS FOR INDUSTRIAL EMISSIONS IN THAILAND

Annex I Standards for industrial emissions in Thailand (Ref. 2)

Substances Sources Proposed Standard Sources Values

Particulate - Boiler & furnace Heavy oil as fuel 0.3 g/Nm 3

Coal as fuel 0.5 g/Nm 3

- Steel manufacturing 400 mg/Nm 3

- Cement plant and calcium 400 mg/Nm 3

carbide plant 400 mg/Nm 3

- Rock and gravel aggregate 400 mg/Nm 3

plants (production capacity more than 50,000 tons/year)

- Other source 500 mg/Nm 3

Smoke opacity Boiler and furnace not exceed 40% Ringlemann scale

Aluminium Furnace or smelter (dust) 300 mg/Nm 3

(AO 50 mg/Nm 3

(dust) 300 mg/Nm 3

(AO 50 mg/Nm 3

Alcohol any source 0.05 Ib/min Aldehyde any source 0.05 Ib/min Ammonia . gas plant 25 ppm Antimony any source 25 mg/Nm 3

Aromatics any source 0.05 Ib/min Asbestos any source 27 ug/Nm 3

Arsenic any source 20 mg/Nm 3

Beryllium any source 10 ug/Nm 3

Carbonyls Burning refuse 25 ppm Chlorine any source 20 mg/Nm 3

Ethylene from production or by usage 0.03 Ib/min Ester any source 0.05 Ib/min Fluorine any source 0.3 lb/ton P,O s

200 mg/Nm 3

10 mg/Nm 3

Hydrogen Chloride any source 0.3 lb/ton P,O s

200 mg/Nm 3

10 mg/Nm 3 Hydrogen Fluoride any source

0.3 lb/ton P,O s

200 mg/Nm 3

10 mg/Nm 3

Hydrogen Sulphide any source 100 ppm Cadmium any source 1.0 mg/Nm 3

Copper any source dust 300 mg/Nm 3

Lead (Cu) 20 mg/Nm 3

Lead any source dust 100 mg/Nm 3

(Pb) 30 mg/Nm 3

0.1 mg/Nm 3 Mercury

dust 100 mg/Nm 3

(Pb) 30 mg/Nm 3

0.1 mg/Nm 3 Mercury any source

dust 100 mg/Nm 3

(Pb) 30 mg/Nm 3

0.1 mg/Nm 3

CO any source 1,000 mg/Nm 3

so2 H 2 S 0 4 production Other activities:1,-. v

500 ppm

- Bangkok and it§ vicinities "0 400 ppm - other area 700 ppm

NO, Combustion source? 1,000 mg/Nm 3

HN0 3 production ' 2,000 mg/Nm 3

and others ' 2,000 mg/Nm 3

Nitric acid any source 70 mg/Nm 3

Organic material any source 0.01 Id/min Phosphoric acid any source 3 mg/Nm 3

Sulfur trioxide any source also in 35 mg/Nm 3

combination with H 2 S 0 4 a s H 2 S 0 4

Sulfuric acid any source 35 mg/Nm 3