SPAN TECHNICAL SPECIFICATIONSuruhanjaya Perkhidmatan Air Negara (SPAN) is a technical and economic...

SPAN – TECHNICAL SPECIFICATION

SPAN-TS XXXX:YYYY

ICS:71.100.80

Disinfection of water -

Electro-chlorination systems

© Copyright 2020 Suruhanjaya Perkhidmatan Air Negara (SPAN)

A document developed by SIRIM for SPAN

SURUHANJAYA PERKHIDMATAN AIR NEGARA (SPAN) Suruhanjaya Perkhidmatan Air Negara (SPAN) is a technical and economic regulatory body for the water supply and sewerage services in Peninsular Malaysia and Federal Territories of Putrajaya and Labuan. The Commission regulates all entities in the water supply and sewerage services industry including public and private water supply and sewerage services operators, water supply and sewerage contractors, permit holders and suppliers of water and sewerage products. SPAN vision is towards a sustainable, reliable and affordable water service for all and with the mission to regulate the water services industry through fair, effective and transparent implementation of Water Services Industry Act 2006 (Act 655). SPAN TECHNICAL SPECIFICATION SPAN Technical Specification (SPAN-TS) is developed according to SIRIM standardisation procedures, which are in line with international practices that ensure appropriate notification of work programmes and participation of interested parties. As a standards development organisation, SIRIM Berhad has extensive expertise in standards research and consultancy which helps industries and businesses meet local and international requirements and practices. SPAN-TS is developed from SPAN initiatives as a regulatory body for the water supply and sewerage services through collaboration with SIRIM which provides requirements, specifications, guidelines or characteristics that can be used to ensure that materials, products, processes and services are fit for their purpose. SPAN-TS is developed through consensus by established committee, which consists of experts in the subject matter. The use of this standard is mandatory, and it is open for adoption by regulators, government agencies, associations, industries, professional bodies, etc. © Copyright 2020 For further info or enquiries on SPAN-TS, please contact: Bahagian Pembangunan Industri Suruhanjaya Perkhidmatan Air Negara (SPAN) Ground Floor and First Floor, Prima Avenue 8, Block 3510, Jalan Teknokrat 6, 63000 Cyberjaya, Selangor Darul Ehsan Tel: 60 3 8317 9333/334/335 Fax: 60 3 8317 9336 E-mail:

© SPAN 2020 - All rights reserved i

Contents

Page Foreword ............................................................................................................................... ii 0 Introduction ............................................................................................................... 1 1 Scope ........................................................................................................................ 2 2 Normative references ................................................................................................ 2 3 Terms, definitions and abbreviated terms .................................................................. 4 4 Materials .................................................................................................................... 5 5 Design criteria………………………………………………………………………………10 6 Installation…………………………………………………………………………………..17 7 Maintenance………………………………………………………………………………...17 8 Service life…………………………………………………………………………………..18 9 Safety ……………………………………………………………………………………….18 10 Performance and test/inspection requirements…………………………………………19 11 Marking………………………………………………………………………………………20 Annex A Salt inspection requirements……………………………………………………..21 Annex B Test method and inspection for electro-chlorination systems………………...22 Bibliography ........................................................................................................................ 25

ii © SPAN 2020 - All rights reserved

Foreword This SPAN-TS was developed by the Project Committee on Disinfection of water - Electro-chlorination systems. This standard was developed with the following objectives: a) to provide a comprehensive standard that prescribes requirements for electro-chlorination

systems; b) to assist the industries to certify their products against a given standard; and c) to provide the regulatory bodies a standard for monitoring of the products. This standard will be subjected to review to reflect current needs and conditions. Users and other interested parties may submit comments on the contents of this standard for consideration into future versions. Compliance with this standard does not by itself grant immunity from legal obligations.

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© SPAN 2020 - All rights reserved 1

Disinfection of water - Electro-chlorination systems 0. Introduction

Electro-chlorination (EC) is the process of electrolysis of brine solution (saturated salt solution/ sodium chloride) and softened water to produce an active chlorine solution, namely sodium hypochlorite (NaOCl). NaOCl is an effective disinfectant and can be used as a substitute for chlorine gas or Calcium Hypochlorite (solid chlorine granules). The production of NaOCl is on-site generation basis. Generation of NaOCl requires salt, water and electricity (direct current type). In these systems, salt is dissolved and used for electrolysis. The electrolysis cells are designed for very low brine feed flow rates, narrow electrode gaps, and produce sodium hypochlorite concentrations approaching one percent. Hydrogen gas, a by-product, is generated when electrolysis occurs on the brine solution. Summary of system resources for EC is shown as in Figure 1.

Figure 1. System resources for EC

The decision to choose on site generation systems should be evaluated through the use of a holistic evaluation, which considers all environmental, social, and economic factors to aid in the decision-making process. These factors may include:

- regulatory requirements (e.g. water quality, permitting); - public health impacts (e.g. emissions from power demands/carbon footprint); - worker and community impacts (e.g., potential releases of hazardous chemicals); - vulnerability/security (e.g., potential thefts of chemicals or attacks on drinking water

treatment systems);

- supply availability/reliability (e.g., ability to obtain the necessary components and consumables);

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2 © SPAN 2020 - All rights reserved

- operational complexity; - quality and quantity of the product being produced; - overall energy consumption of the system; - initial investment, maintenance and operating costs; - skill and infrastructure available; - safety of operations; and - specific local constraints or opportunities. This technical specification was developed as a guide to qualify equipment for these treatment systems. The technical specification provides the requirements on the material used for the construction of the equipment, the design criteria for electro-chlorination equipment, the performance, acceptance criteria and test requirement for type of equipment, the installation, maintenance, service life, the safety consideration during installation and operation of equipment, and the requirements on marking of equipment that need to be followed by equipment manufacturers/supplier.

1. Scope

This technical specification provides the requirements for electro-chlorination (EC) which generates liquid sodium hypochlorite NaOCl, intended for disinfection of water in water supply systems.

It covers the material, design criteria, installation, maintenance, service life, safety, performance requirement and testing, and marking.

2. Normative references

The following normative references are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the normative reference (including any amendments) applies. Food Act 1983 Food Regulation 1985 Occupational Safety and Health Act 1994 Factories and Machinery Act 1967 MS 628-2, Plastics piping systems for water supply and for buried and above-ground drainage and sewerage under pressure - Unplasticized poly(vinyl chloride) (PVC-U) - Part 2: Pipes MS 628-3, Plastics piping systems for water supply and for buried and above-ground drainage and sewerage under pressure - Unplasticized poly(vinyl chloride) (PVC-U) - Part 3: Fittings MS 740, Specification for hot-dip galvanized coatings on iron and steel articles

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MS 1058-2, Specification for Polyethylene (PE) piping systems for water supply. Part 2: Pipes MS 1058-3, Specification for Polyethylene (PE) piping systems for water supply. Part 3: Fittings MS 1115, Specification for table salt MS 1225-Part 1, Polyethylene (PE) tanks for cold water storage; Part 1: Capacity up to 600G MS 1225- Part 2, Polyethylene (PE) tanks for cold water storage; Part 2: Capacity more than 600G MS 1241, One piece Glass-fibre Reinforced Polyester (GRP) water tanks nominal capacity of 100 000 litres and below. -Specification MS 1390, Glass-fibre Reinforced Polyester panels and panel water tanks. - Specification MS 1757-1, Chlorinated Poly(Vinyl Chloride) (PVC-C) plastic piping system. Part 1: Specification for schedules 40 & 80 pipes MS 1757-3, Chlorinated Poly(Vinyl Chloride) (PVC-C) plastic piping system. – Part 3: Specification for schedule 80 pipe fittings MS 1736-2, Plastics piping systems for hot and cold water installations. Cross-linked Polyethylene (PE-X). Part 2: Pipes MS 1736-3, Plastics piping systems for hot and cold water installations. Cross-linked Polyethylene (PE-X). Part 3: Fittings ISO 4097, Ethylene-propylene-diene (EPDM) - Evaluation procedure

ISO 4633, Rubber seals - Joint rings for water supply, drainage and sewerage pipelines - Specification for materials

ISO 10639, Plastics piping systems for pressure and non-pressure water supply - Glass

reinforced thermosetting plastics (GRP) systems based on unsaturated polyester (UP) resin

ISO 28765, Vitreous and porcelain enamels - Design of bolted steel tanks for the storage or

treatment of water or municipal or industrial effluents and sludges

BS EN 1796, Plastics piping systems for water supply with or without pressure. Glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resin (UP) BS EN 13280, Specification for glass fibre reinforced cisterns of one-piece and sectional construction, for the storage, above ground, of cold water BS EN 16370, Chemicals used for treatment of water intended for human consumption - Sodium chloride for on site electochlorination using membrane cells

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ATEX Equipment Directive Codex Alimentarius for food grade salt

3. Terms, definitions and abbreviated terms 3.1 Terms and definitions For the purposes of this standard, the following terms and definitions apply. 3.1.1 disinfection Process which removes or renders inactive pathogenic microorganisms or parasites. Disinfection of water treated in potable water treatment plants generally take place after filtration process. Dosage of NaOCl as a disinfectant, varied according to the chlorine demand/ disinfectant demand in the water. 3.1.2 electro-chlorination Method of disinfectant generation, on site basis. Sodium Hypochlorite NaOCl is produced using electrolysis process. In this method, brine solution (or in some cases, sea water) is converted into hypochlorite solutions. When direct current is passed through electrodes immersed in solution containing brine, electrolysis of sodium chloride takes place. The reaction can be put forth as:

NaCl + H2O + Energy (Direct current) → NaOCl (aqueous) + H2 (gas) 3.1.3 electrolysis Process that decomposes a chemical compound into its elements or produces a new compound by the action of an electrical current. The electrical current is passed through an electrolytic cell and oxidation/reduction reactions occur at the electrodes. E.g., water can be decomposed into hydrogen and oxygen, or a metal can be electroplated by electrolysis. 3.1.4 hydrolysis Disinfection by sodium hypochlorite. NaOCl + H2O → HOCL + NAOH 3.2 Abbreviated terms CaCo3 calcium carbonate Cl2 chlorinated (chlorine) EPDM ethylene propylene diene monomer FRP fibre-reinforced plastic H2 hydrogen gas H2O water

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HOCL hypochlorous acid LLDPE linear low-density polyethylene NaCl sodium chloride (salt) NaOCl sodium hypochlorite UV ultraviolet PE polyethylene PE-X crosslinked polyethylene PTFE polytetrafluoroethylene PVC poly(vinyl chloride) PVC-C chlorinated poly(vinyl chloride) PVC-U unplasticised poly(vinyl chloride) PVDF poly(vinylidene fluoride)

4. Materials 4.1 General For any other material used in the field of application of this technical specification, all requirements of this technical specification and any other relevant requirements specified by the authority shall be met. Local conditions may require the use of particularly durable materials; this being subject to special agreement between EC supplier and client. Durability can be achieved by the use of materials inherently resistant to corrosion. Where possible, anti-corrosion protection shall form part of the manufacturing process. 4.2 Raw materials See Table 1. 4.3 Materials for specific components See Table 2.

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Table 1. Raw materials

No. Type of materials Minimum requirement/grade Standard/

Specification*

1 Salt/Sodium chloride Food grade quality Food Act 1983 and Food Regulation 1985/Codex Alimentarius for food grade salt/MS 1115/BS EN 16370

Halal Requirements for registration of chemical shall be include Halal Certificate issued by:

(i) Department of Islamic Development Malaysia (JAKIM); or

(ii) local Islamic bodies recognised by JAKIM; or

(iii) foreigner bodies recognised by JAKIM.

2 Water Non chlorinated water/

Softened water

*Other specification can be used provided the requirement of this standard shall be met. However, it should be noted that EC systems users shall always confirm with the EC supplier if common food grade salt of certain quality could be used in their EC system as to avoid any misunderstandings on the suitability of salt used. The quality of salt used could have a bearing on the electrodes/cells warranty of lifespan.

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Table 2. Materials for specific component

No. Component Material Minimum grade

Standard/ specification*

1 Brine tank PE/FRP or any other relevant

standard materials that compatible

with the salt.

LLDPE MS 1225-Part 1 and MS 1225- Part 2/ manufacturer specification

2 Brine/dosing pump

Diaphragm pumps: Recommended as per table below or equivalent.

Peristaltic Pumps: EPDM Hose,

EPDM base polymer or equivalent.

Other equivalent pumps such as

centrifugal or magnetic driven pumps

to be as per recommended

specifications by manufacturer

suitable for sodium hypochlorite.

Sodium hypochlorite

Brine solution

Pump head

PVDF PVC

Ball check

PTFE (Teflon)

Ceramic

Diaphragm

PTFE (Teflon)

PTFE (Teflon)

O-ring PTFE (Teflon)

PTFE (Teflon) or Viton

Manufacturer specification

3 Cell plates Anodes and cathode with titanium as a base metal coated with a precious metal oxide.

Manufacturer specification

4 Blower PE/FRP/Aluminium ATEX Equipment Directive

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Table 2. Materials for specific component (continued)



5 Product tank Materials which are resistant to sodium hypochlorite corrosion: FRP with chemical resistant vinyl ester resin. PE/HDPE PE-X/ PVC/PVC-U FRP lining (Glass coated/ Glass lined/ Glass fused/ Epoxy coated/ Epoxy lining) For outdoor storage, tanks are recommended to be made with a UV resistant paint, UV stabilised resin such as resin # 880059, and/or polyurethane foam insulation and mastic coatings equipped. Rubber lined tanks are not recommended as the hypochlorite’s oxidation characteristics may have effect on the rubber to be brittle.

Minimum thickness 5 mm Should be rated to 1.35 specific gravity

BS EN 13280/ /MS 1390 (FRP)/MS 1241 MS 1225-1/MS 1225-2 (PE/HDPE) Manufacturer specification ISO 28765

6 Product tank component materials:

Piping PVC PE PE-X FRP/GRP PVC-C

MS 628 MS 1058-2 MS 1736-2 ISO 10639/BS EN 1796 MS 1757-1

Fitting PVC PE PE-X FRP/GRP PVC-C

MS 628-3 MS 1058-3 MS 1736-3 ISO 10639/BS EN 1796 MS 1757-3

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Table 2. Materials for specific component (concluded)



Gasket Viton® or PTFE (Teflon®) EPDM or equivalent

Manufacturer specification ISO 4097 ISO 4633

Bolt All internal bolts, nuts, washers and anchor bolts which are in contact with water shall be of stainless steel. Hot dipped galvanised steel in accordance with MS 740 or equivalent standard; or of better grade material consistent with adjoining material.

Minimum grade SS304

Supplier certificate MS 740

*Other specification can be used provided the requirement of this standard shall be met.

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5. Design criteria Design of electro-chlorination equipment vary from one manufacturer to another. To accommodate these varied requirements, systems are generally configured with the following standard components and operate in the manner described below: 5.1 Salt/brine solution tank The salt/brine solution tank is used for batching and storage of brine solution. The salt/brine tank provides the required salt for electrolysis. Automated refill of the brine tank with softened water is recommended. The brine tank should be equipped with an ultrasonic level or other level sensor, side manhole, overflow and drain for operation and maintenance. The drain valve shall be positioned to allow for complete emptying of the tanks. Caged ladders, stairway and platforms with hand railing should be provided for access to the salt loading opening on the tanks. Visual inspection of the tank content will give the operator an indication for the need to fill the tank with salt. Example on the design calculation:

To produce 1 kg of Cl2 requirement: Salt = 3 kg of salt Electric = 4.4kwH Softened water = 125.24 L

Salt Requirement: Total dry salt consumption (kg/day) = Total required chlorination capacity (kg/hr) x 3 kg of salt x 24

Assuming brine density = 1 200 kg/m3 Brine solution required (m3/day) = Dry salt consumption/brine density If required for 3 days: = Brine solution required (m3/day) x 3 day

5.2 Brine pump The pump that can used either the centrifugal pump type, magnetic driven, hydraulic and mechanical diaphragm pump or peristaltic type for metering the feed of the brine. The pump may come with the accessories such as calibration column, Y-strainer, pulsation dampener, back pressure valve and pressure gauge. Properly sized peristaltic or brine feed pump may not require pulsation dampener or backpressure valves. The use of a leak detector switch in the lubricant compartment of the pump is recommended to detect hose failures/ruptures. 5.3 Water flow 5.3.1 Incoming water 5.3.1.1 Supplier shall ensure sufficient water pressure available to suit the systems requirements. For systems that utilise the incoming water pressure ( softened water) to deliver the product to the product storage tanks directly from the electrolyser cells, one have to consider that the pressure has to be sufficient to carry the product to the inlet of the product tank.

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5.3.1.2 Quantity or flow of the water supplied shall be consistently available for the EC system. It is recommended that the water used for EC system, to be independent from any other usage at the treatment plant. Shared usage of water supply may cause the EC system to be halted due to temperature and conductivity limitations. EC system supplier should emphasis in writing to client on these water supply requirements to avoid any disputes during project execution. Supplier shall ensure there is clean water for NaOCl production in the event of the water treatment plant (WTP) “restarting” after the it shuts down for maintenance, power supply interruptions or whatever possible reasons. 5.3.1.3 It is highly recommended that the EC system shall has its own independent stored clean water supply for at least 3 hours of EC production needs. The quantity of water needed for 3 h of EC production is subject to the EC system’s capacity. It is recommended that for every 1 kg/h of chlorine production equivalent, 170 L of water stored per hour. 5.3.2 Softened water 5.3.2.1 Soft water shall be used for electro-chlorination process (see Figure 2 for example of water softener). Softeners should be supplied with under a set of “duty-standby” units for every EC system installed. To avoid interruption to the EC production process, the softeners shall be automatically switched over when one unit of softener is under regeneration process. Frequency of softener’s regeneration shall be based on:

− softened water hardness measurement; or

− timer based; or

− flow based. This can be accomplished by using dual resin tanks with automatic changeover during regeneration cycles shown in Figure 3. 5.3.2.2 Softened water requirement varies for each EC system. User shall request from the EC system supplier on the softened water input requirement for the system supplied.

Figure 2. Water softener

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Figure 3. Typical duplex softening system (courtesy of Black & Veatch)

5.3.2.3 The high pH within the cell during electrolysis will rapidly precipitate dissolved calcium and magnesium salts naturally present in some waters, forming scale on the electrode surfaces and reducing electrolysis efficiency. Calcium and magnesium ions in the water can develop into a hard scale in piping systems and other equipment. In on - site generation systems, the scale will coat the electrodes in the cells and, over time, reduce their efficiency, thus increasing their electricity demand. It can also inhibit flow through the cell and cause blockage. When the sodium hypochlorite and hydrogen cannot exit the cell, pressure will rise and, if ignored, the cell may burst.

5.3.2.4 The use of softened water is for prevention of calcium and magnesium hardness from depositing onto the electrode’s surface. It extends the service life of the electrode cell and reduce the frequency of the need for chemical cleaning. Use of hard water may increase the potential of electrode damage.

5.3.3 Water cooling system 5.3.3.1 When required, EC systems manufacturer/supplier should provide the system’s operating parameter’s requirements which includes the incoming water supply’s temperature. Water supply temperature is important as it has direct effect on the product (NaOCl) temperature, the electrode package (anode and cathode metal plates), the electrode packages housing (cell tube and components) and plastics pipe works after the cell package. 5.3.3.2 EC system users should always take note on the incoming water temperature requirement in order to prevent any damages to the cell package and to avoid generation to chlorates in the product. Water cooling systems could be of chiller (water or air cooled) or heat exchanger type, subject to the suitability, costs and operational concerns of the user. 5.4 Cell 5.4.1 Cell (electrolytic cell) designs vary from one manufacturer to another. The materials used to construct the cell body shall be made of FRP/PVC or any other relevant standard materials. The materials shall be resistant to the type of chemical it comes into contact with, whether water, brine solution or sodium hypochlorite. Materials used to construct the electrolyser cell housing should be able to withstand the temperature of the fluid when electrolysis is in process.

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5.4.2 The electrolyser system is designed to produce hypochlorite with a chlorine concentration minimum 6 % w/v. There should be low liquid level sensor in the cell, high rectifier voltage, cell high temperature sensor to safeguard the shutdown sequence of the electrolytical cell. 5.5 Transformer /rectifier 5.5.1 Power supply to the EC system shall be independent and shall not be shared with other system in use. Alternating current (AC)/direct current (DC) rectifiers converts AC to DC. DC current is supplied to the electrodes. DC is required for electrolysis process to attract anions at the anode and cations at the cathode as the electrodes are maintained at a constant polarity. Use of AC would lead to uneven deposits of ions at the electrodes and complete electrolysis process would not take effect. 5.5.2 EC systems installed shall have surge protection systems. At places where the power supply is inconsistent or have regular power outages, it is recommended to have a voltage regulator installed for the EC systems. 5.5.3 It is recommended to have a separate/individual power meter installed at the main power supply control panel to monitor the actual power consumption of the EC system and its related peripherals such as water cooling system, water booster pumps, brine pumps, air dilution blowers and other components. Any abnormalities in terms of power usage for the EC system could be detected and early rectification could be useful to avoid any major damages to the systems. 5.5.4 In the event of any of the EC system’s main component failure, the rectifier(s) shall shut down and cut off the power supply immediately. The communication between the electrolyser’s key components and the rectifier shall be designed seamlessly for safety shutdown features. 5.5.5 The EC system shall have indication for each of the rectifier(s) for:

− real time operating voltage;

− real time amperage;

− voltage operating range and set points; and

− amperes operating range and set point. 5.5.6 The rectifier shall have the following safety features:

− output voltage monitored by Programmable Logic Controller (PLC); and

− output current monitored by PLC. 5.5.7 The design shall take into account nominal power consumption of all electrical drives and power consumption. 5.6 Hydrogen venting and blowers 5.6.1 A degassing chamber at cell or hydrogen vent piping/degassing pipes connected to the cell shall be provided which are connected to blowers for forced air dilution to the system. The blowers can be centrifugal type by direct motor driven type or belt driven type. Proper

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mounting of the blowers shall be considered. The air blowers should be sized to dilute the generated hydrogen gas to less than 1 % by volume of hydrogen or 25 % lower explosion limit (LEL). Each fan should be rated at not less than 100 times the maximum hydrogen production rate of an electrolyser. 5.6.2 To prevent corrosion of the blower and prevent hypochlorite fumes from entering the room, it is recommended that a check valve with drip leg be installed. Figure 4 below shows clear PVC drip leg tubes and check valve bodies. This assembly is designed to protect the blower from corrosion.

Figure 4. PVC drip leg tubes and check valve bodies

5.6.3 The vent pipes termination should include insect screen to prevent intrusion of insects, birds or small animals. It should face down to prevent rain water from pouring in. The method for monitoring the proper amount of air flow through the vent stack dilution line and/or the tank outlet dilution line is with an orifice plate. This flow detection method uses the following components.

− orifice plate spool assembly which is an orifice plate bolted between two flanges;

− differential pressure switch; and

− tubing to connect the orifice plate ports to the differential pressure switch ports.

An air flow switch can also be provided for the monitoring purposes. 5.6.5 All tanks should be vented. The vent should exceed the size of the tank’s largest inlet or outlet nozzle by two inches. The vents should have a vinyl insect screen attached to the end to keep debris or insects out of the tank. 5.6.6 The most common cause of damage to FRP and plastic tanks is lack of venting during filling or emptying operations. Every atmospheric pressure rated tank shall be protected at all times by properly sized vent pipes in order to prevent build-up of pressure or vacuum conditions. This includes not only the ingress of air and egress of gasses when emptying and filling the product tank, but is also required under normal conditions when changes can occurs in the temperature to the contents of the product tank consequent to the elevation of temperature newly generated product when discharged to the tank.

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5.6.7 The system should be equipped with a hydrogen separation equipment for safety purposes. Hydrogen gas generated shall be diverted to atmosphere immediately upon generation. For safety purposes, hydrogen accumulation along with the product generated in the product delivery pipe into the product storage tanks is not allowed. The Electrolyser system shall shut down with alarm when the hydrogen gas (H2) are not discharge properly or there is a blockage. The air blower used for the hydrogen removal shall conform with ATEX Directive as hydrogen gas is an explosive substance. Hydrogen gas shall be diluted to < 4.1% (lower than lower explosion limit LEL) before released into the atmosphere. 5.8 Pipe work The purpose of the internal distribution and brine removal piping is to maximise the salt dissolving rate. Due to the piping arrangement, dissolver internal piping is normally field erected to assure damage free equipment for start up operation of the dissolver. The supplier/users shall confirm that:

− all piping is installed and properly connected;

− all threaded and flanged connections are tight; and

− hydrostatically test all piping to site specified pressures. Another best practice is to ensure piping for liquid streams is separated from electrical feed lines and that the pipe runs are not located above rectifiers or other electrical components. Pipe, valves and fittings should be designed for severe sun exposure (UV rays) and ozone conditions in rare occasions. 5.9 Systems control The control panel should control and(or) monitor all functions and operational parameters including, but not limited to the following: a) cell safety devices such as cell temperature; b) transformer/rectifier; c) DC amperage and voltage; d) hypochlorite tank levels; e) hydrogen dilution system and safety; f) hydrogen detection; g) alarm history; h) softener water and brine flow; i) conductivity of brine solution entering the electrolyser cell; j) level of brine and storage tank; k) password control for adjustment of parameters working range of brine tank levels, product tank levels, cell voltage and amperes range and cell temperature; l) real time, brine tank level readings or indicators either on localised panel display or via

HMI; and m) water pressure into the cell.

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5.10 dosing system 5.10.1 Sodium hypochlorite (the product) dosing system shall be of duty - standby basis. Materials of construct for the dosing system and its delivery line shall be hypochlorite resistant (corrosive resistant). Any metallic component is not recommended. 5.10.2 Positive displacement dosing pumps or motive water-ejector system are recommended. Dosing system for hypochlorite shall be sized based on the % concentration of the product generated in line with the dosage required by the user. Under normal conditions, a chlorine equivalent dosage of 3 ppm to 5 ppm is used in Malaysian potable water treatment plants. 5.10.3 Required dosing rate for pumps for pre and post design capacity = Pre or post chlorine dosage per % hypo dosing requirement or L/hr of % sodium hypochlorite converted from required chlorine dosage in kg/hr. Pumps shall be sized with allowance to the required % sodium hypochlorite dosing capacity. 5.10.4 The hypo dosing system operations shall be independent of the EC operations. However, the hypo dosing system could be linked to the treatment plants SCADA systems. 5.11 Product storage 5.11.1 Product storage system shall be of minimum 2 units, for maintenance and stock security purposes. Product storage tanks shall be equipped with level sensors to provide real time level readings to the EC systems controls. For systems that has air blowers installed to dilute the hydrogen at the product storage tanks, it is compulsory that all tanks shall be sufficiently ventilated by the air blower. 5.11.2 In any event where the blower is non-functional, the EC system shall stop operating, for safety reasons. 5.11.3 Storage system designed shall be of First In, First Out (FIFO) basis. It is recommended that the storage tanks to be sheltered from direct sunlight. Ambient temperature of storage area should be below 40º C. These systems are designed to provide usually 1 to 3

days of stored sodium hypochlorite but the designed is depending on the specific plant location, layout, operations, and applicable regulations/legislations. 5.12 System layout The space requirements of an electro-chlorination system should include, in addition to the system components, the recommended maintenance clearances for each item of equipment. A sample layout is presented in Figure 5.

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Figure 5. Typical layout of on site-generation system (courtesy of Black & Veatch) The system illustrated above is housed in a closed process building. The sodium hypochlorite storage tanks and the brine tanks are provided with containment. The remaining equipment may be installed inside a curbed area to contain incidental spills.

6. Installation The on-site installation of the EC and its peripherals shall comply with the manufacturer’s recommendations and local authorities’ procedures and safety regulations. During commissioning of the EC system, no open flame or sparks (static of live) generating equipment shall be present. System shall not be commissioned if the air blower/hydrogen thinning system is not operational.

7. Maintenance It is highly recommended that EC system users to have periodic maintenance on the EC system and its components according to the manufacturer’s recommendation. Prior to purchase or installation of the EC system, users are recommended to obtain from the manufacturers/suppliers, the spare parts lists, period of service requirement, replacements parts and its costs. Maintenance and service works shall be from manufacturer authorised and competent personnel to avoid any accident or damage to the systems. EC system users are recommended to request for certificate of competency of the servicing personnel.

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8. Service life When EC systems are well maintained, the expected lifetime of the electrolytic cell is typically between 5 and 7 years. Feedstock quality, in this case the salt and water used to form the brine and feed the cell, is the primary factor that will determine both the required maintenance cycles for the EC systems as well as the electrolytic cell performance and lifetime. Several components of either the salt or the water used to feed an EC system can produce deleterious effects on the electrolytic cell, with the three primary mechanisms of cell failure being anode passivation, electrode wear, and formation of deposits within the cell.

9. Safety The purpose of the safety section is to provide a general overview of the safe operation of the plant. The plant shall follow the best safety, health, and environmental standards and practice in the industry. 9.1 The plant shall be complying with the Occupational Safety and Health Act, 1994 (OSHA 1994) and Factories and Machinery Act, 1967 (FMA 1967), and all the related regulations as well as relevant code of practice and guidelines made under the two Acts and its regulation. The Acts provide general duties of employers to the employees and to persons other than the employees (hereafter referred to as operators). The Acts also imposed general duties of designers, manufacturers, importers, and suppliers to ensure the plant is designed and constructed to be safe and without risk to safety and health. All the equipment and component of the plant shall be designed and constructed in accordance with the codes or standards recognised or recommended by relevant authorities’ bodies. 9.2 One of the general duties of an employer is to carry out a risk assessment. The employer shall identify the potential hazards arising from the plant, evaluate the risk associated with hazards identified, and implement risk control in order to ensure the safety of the operations, reduce the risk of injury or illness to operators and damage to the equipment, property, and environment. Potential hazards at the plant primarily from the use of machinery and equipment, work process, or work activities performed by the operators. 9.3 A risk assessment should consider the following but not limited to:

− internal temperature;

− internal pressure;

− flow rate;

− alarm systems;

− safety shutdown;

− over-pressure protection;

− gas production;

− commissioning/ maintenance/ calibration activities;

− power supply to electrodes;

− proximity/ orientation to surrounding persons and equipment; and

− raw material and chemicals handling.

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9.4 The risk control can be implemented by referring to the hierarchy of control in which priority is given from the highest level of protection to the least, which is elimination, substitution, engineering controls, administrative controls, and personal protective equipment (PPE).

9.5 Employer shall also consider the risk of accumulation of explosive gases from the operation of the plant and provide mitigation plans. Appropriate measures shall be taken into consideration and/or explosion-proof equipment shall be selected. 9.6 Safe work procedures which describe the process and safe work measures should be prepared to allow operators to perform their task safely. 9.7 Information, instruction, and training to the operators shall be provided by the employer to ensure safety standard is observed. Employer needs to make available information on the chemical especially of any risk to which their inherent properties may relate to the safety and health during the use, handling, processing, storage, transportation, or disposal. Safe work procedures and safety data sheet (SDS) shall be made visible and posted in a protective envelope on the wall of the storage. The dosage of installation for the use of the operator and other personnel of water suppliers shall also be made available. 9.8 It is important to follow best practices for chemical handling including the use of suitable personal protective equipment (PPE), such as respiratory protection, gloves, glasses, safety shoes, and protection clothes. There shall be a provision of showers near the working area for emergency purposes. 9.9 First aid box and eyewash fountain shall be provided outside the chlorinator room. 9.10 Housekeeping, repair and equipment maintenance programme shall be well established. 9.11 Maintenance and services work shall be conducted by a competent and/or trained person.

10. Performance and test/inspection requirement The expected performance for electro-chlorination according to design shall be as given in Table 3.

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Table 3. Acceptance criteria for electro-chlorination systems

Parameter Acceptance criteria Test method/

Inspection

Salt Food grade quality Annex A

Water hardness Less than 10 ppm CaCO3 Annex B

Product quality pH range: 9 - 10.5

Annex B Minimum concentration: 0.6 %w/v

Specific gravity: 1.35

System capacity As rated Annex B

Energy consumption As rated Annex B

11. Marking Each equipment shall at a minimum be marked with the following information: a) manufacture’s name or trademark;

b) manufacturing serial number; c) installation date (MM/YY);

d) date of systems commissioning; e) systems capacity in Kg Cl2/hr equivalent; and f) citation of this standard.

The markings shall be printed, made visible and adhered to the equipment.

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Annex A (normative)

Salt inspection requirement

A1. Marking and labelling

A1.1 The salt shall be supplied in clean dry packing. Packaging material should be double

layer, water resistant with inner layer of polyethylene liner. Each salt bag shall have markings

as the following:

a) pure dried vacuum salt, trade name and grade type;

b) net weight;

c) country of origin;

d) production lot/batch number;

e) date of manufacturing or packing; and

f) other markings as required by law (i.e. halal).

A2. Storage

The salt bags shall be delivered and protected from sun and rain. Storage containers during

delivery shall be compatible and will not affect the purity of the salt. The means of storage in

transit and delivery shall not have been used previously for any toxic and hazardous materials.

A3. Analysis

A Certificate of Analysis (COA) on the quality of the salt shall be submitted for every

consignment. A comprehensive COA by a accredited laboratory shall be submitted on every

6 months basis form one of the lots supplied.

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Annex B

(normative)

Test method and inspection for electro-chlorination systems

B1. Water hardness

B1.1 Water hardness shall be maintained below 10 ppm CaCO3 in order to prevent system

scaling and to satisfy the maintenance terms of the system warranty.

B1.2 Conduct a test for water hardness according to an established laboratory method.

B1.3 This test allows the analyst to use different sample volumes to vary equivalencies. Select the appropriate sample volume. B1.4 Record ppm hardness as CaCO3.

B2. pH B2.1 pH shall be tested according to an established laboratory method. B2.2 pH range shall be from 9 to 10.5.

B3. Specific gravity B3.1 The purpose of the specific gravity test is to measure the ratio of water to salt within aqueous brine solution in order to economically and efficiently produce sodium hypochlorite. By obtaining an accurate specific gravity reading, the operator can determine the amount of salt and make adjustments accordingly. B3.2 Conduct a test according to the appropriate method as provided by the system’s manufacturer or commercially available test kits for sodium hypochlorite. B3.3 Record the measurements as shown on by measuring equipment i.e. thermometer and hydrometer.

B3.4 Reading the salinity chart

Salinity chart is used to calculate the amount of salt in aqueous solution in units of grams per liter (10 g/L = 1% NaCl). By using this chart, ones can learn whether need to add or subtract salt to the solution.

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NOTE. This test can be conducted with either the non-electrolysed "pure" brine solution or the output of the electrolytic cell after producing sodium hypochlorite at dedicated concentration. The specific gravity of the sodium hypochlorite is roughly the same as that of the non-electrolysed brine solution.

B3.5 Gather the temperature and hydrometer readings that have measured in order to cross reference them with the salinity chart.

B4. Chlorine testing

B4.1 The purpose of this testing is to determine the percentage of total available chlorine in sodium hypochlorite generation output solution by using the established method such as drop count method of chlorine bleach testing.

B4.2 The result can be calculated as follows: Available chlorine, % = 0.05 x Number of drops available chlorine (parts per thousand) = 0.5 x number of drops

B5. System capacity B5.1 Calculation for determining the EC system output in terms of Kg/hr of chlorine

equivalent is as follows:

- Determine the concentration of the NaOCl (sodium hypochlorite) generated from the system via test method provided by the system’s manufacturer or commercially available

test kits for hypochlorite concentration.

- Assume the concentration is X gm/L.

- Measure the output flow (liquid NaOCl) of the EC system in terms of L/h. Assume if output is Y L/h.

B5.2 Therefore, to calculate the actual capacity of the EC system, the following formula is used:

X (gm/L ) × Y(L/hr) = XY gm/hr of Cl2 equivalent output of EC system

EXAMPLE. Concentration of NaOCl generated was measured to be 7.5 gm/L. Output flow of

EC system was measured to be 250 L/h. Therefore, capacity output of EC system is calculated

to be:

7.5 gm/L × 250 L/hr = 1 875 gm/hr of Cl2 equivalent. i.e.,1.875 kg/hr system.

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B6. Energy consumption B6.1 Energy conversion efficiency (ECE)

The energy used by a cell is calculated by measuring the voltage (V) and current (I) across the cell over a fixed time (t) and calculating the energy used (after suitable conversions of units to yield kW.h) as:

Energy = V × I × t The total (mass) of available chlorine produced over that same timeframe (t) is determined from the volume and available chlorine concentration of the solution produced in time t as described above. ECE is then calculated as:

ECE = Energy (kW•h)/mass of total available chlorine produced ECE is used to estimate the electrical energy requirements and energy costs of electro-chlorination operation.

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Bibliography [1] EN 14805:2009, Chemicals used for treatment of water intended for human

consumption – Sodium chloride for on site electrochlorination using non- membrane technology

[2] BS EN 901:2013, Chemicals used for treatment of water intended for human

consumption - Sodium hypochlorite [3] BS EN 16370:2013, Chemicals used for treatment of water intended for human

consumption – Sodium chloride for on site electrochlorination using membrane cells [4] Conversion to on-site sodium hypochlorite generation, Water and wastewater application, Lewis publishers [5] Development of a small-scale electro-chlorination system for rural water supplies,

University of the Western Cape [6] M20, Water chlorination/chloramination practices and principles, AWWA [7] M65, On-site generation of hypochlorite, AWWA [8] White’s handbook of chlorination and alternatives disinfectants,5th edition, Wiley [9] Water treatment manual: Disinfection, Environmental Protection Agency, Ireland

© SPAN 2020 - All rights reserved

Acknowledgements SPAN and SIRIM Berhad would like to thank the organisations who have contributed their ideas, time and expertise in the development of this technical specification. Mr Izaidi Ahmad (Chairman) Suruhanjaya Perkhidmatan Air Negara

(SPAN) Ms Noraslina Mat Zain (Technical Secretary) SIRIM STS Sdn Bhd Ms Muzalifah Mohamad (Project Coordinator)

Suruhanjaya Perkhidmatan Air Negara (SPAN)

Ir Edwin Choo Greendex Sdn Bhd Ms Noor Asriah Ramli/Ms Norhazimah Mohamad

Jabatan Keselamatan dan Kesihatan Pekerjaan

Ms Shirley Heng Shin Air PBA PP Sdn Bhd Mr Roslan Azizan/Ms Wan Norisah Wan Awang

SIRIM QAS International Sdn Bhd (Product Certification and Inspection Department)

Ms Rohaidah Ibrahim SIRIM QAS International Sdn Bhd (Testing Services Department)

Datuk Chan Kam Wai/Datin Choo Mei Foo Solidium Sdn Bhd Mr Ahmad Farhan Ahmad Misbah/Mr Mohd Jamil Esmahadi/

Syarikat Air Melaka Sdn Bhd

Prof Madya Ir Dr Faridah Othman/ Dr Wan Zarina Wan Jaafar

Universiti Malaya

© Copyright 2020

All rights reserved. Unless otherwise specified, no part of this module may be reproduced or utilised in any form or by any means, electronic or mechanical, including photocopying, recording or otherwise, without prior written permission from SPAN.

SPAN TECHNICAL SPECIFICATIONSuruhanjaya Perkhidmatan Air Negara (SPAN) is a technical and economic...

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Transcript of SPAN TECHNICAL SPECIFICATIONSuruhanjaya Perkhidmatan Air Negara (SPAN) is a technical and economic...