This document provides the system description for the Water Treatment System for NGHI SON 2 Thermal Power Plant. Raw sea water from CW pump is directly fed to the pretreatment system and seawater must be treated by Lamella Clarifier, Ultra Filtration (UF), and Sea water Reverse Osmosis (SWRO) process as a source for the service water required. The service water shall be transfer to Demineralized Water Treatment System to make demineralized water which is consist of Brackish Water Reverse Osmosis (BWRO), Degasifier and Mixed Bed Polisher
INTRODUCTION
This document provides the system description for the Water Treatment System for NGHI SON
Raw seawater from the CW pump is directly supplied to the pre-treatment system, where it undergoes essential processes including Lamella Clarifier, Ultra Filtration (UF), and Sea Water Reverse Osmosis (SWRO) to produce the service water needed.
The service water shall be transfer to Demineralized Water Treatment System to make demineralized water which is consist of Brackish Water Reverse Osmosis (BWRO), Degasifier and Mixed Bed Polisher.
SYSTEM / COMPONENT DESCRIPTION
GENERAL REQUIREMENT
The water treatment system plant is designed for the production of service water, potable water, and demineralized water and consist of the following major equipment
• Pretreatment system and associated chemicals: Lamella Clarification system, Ultra Filtration (UF) system, coagulation and flocculant aid chemcial feed systems and sludge treatment system
• RO system and associated chemicals which consist of SWRO trains, antiscalant chemical feed systme, sodium bisulfite chemical feed system, Energy Recovery Device (ERD) with booster pumps, SWRO permeate tank,
• Demineralzied water system consisting of BWRO trains, a degasifier with blowers, mixed bed polisher (MBP) trains, caustic and acid chemical regeneration feed systems,
• Potable water system consisting of activated carbon filters and chlorination.
DESIGN AND FLOW PATH DESCRIPTION
Raw water passes through a static mixer, coagulation tank, flocculation tank, a lamella clarifier, and finally is collected into clarified water pond
Ferric chloride (FeCl3) and sodium hypochlorite (NaOCl) are directly dosed into the coagulant tank, while hydrochloric acid (HCl) is introduced into a static mixer on the raw water feed line This static mixer facilitates effective mixing of the acid before the treated raw water flows to the clarifier Additionally, an agitator in the coagulation tank ensures thorough mixing of the chemicals.
The effluent from the coagulation tank flows into the flocculation chamber, where a gentle agitator facilitates slow mixing In this tank, a coagulant aid, such as polymer, is gradually combined with the coagulated water to enhance the agglomeration of smaller flocs into larger ones This process of floc formation is crucial, as it improves the settling of suspended solids in the downstream clarifier.
Dosing rates for both coagulant and coagulant aid (polymer) is determined at the site based on jar tests and will be adjusted seasonally to account for changing water quality
Chemically pretreated water is directed through a basin equipped with inclined (Lamella) plates, facilitating the separation of solids As water ascends through these plates, solids descend, allowing for efficient separation The sludge that collects at the bottom of the clarifier is then pumped to a thickener using a sludge disposal pump for further treatment via a filter press.
The clarified water quality to be;
The clarified water (Turbidity≤4 NTU) is collected in a clarified water pond where it is pumped to the UF unit for further filtration and solids removal The filtrate (Turbidity≤0.1 NTU,
SDI≤3) from the UF is directed to the filtered water pond UF cleaning water source for the
UF will be filtered water stored in the same tank Air scour is employed to reduce the cleaning wastewater and extend the service run
The UF filtrate quality to be;
The SWRO system utilizes sodium bisulfite to dechlorinate the feedwater, ensuring the absence of residual chlorine before it enters the system Additionally, antiscalant is incorporated to mitigate the scaling potential of various ions, enhancing the overall efficiency and safety of the process.
The SWRO permeate quality to be;
The SWRO permeate is directed to the plant and fire water storage tank to serve as a reliable source of service water Additionally, it is channeled to the SWRO permeate tank, which supports the demineralized system comprising BWRO and MBP for boiler makeup water.
The BWRO permeate quality to be,
The permeate from the BWRO trains is directed to a permeate header, which supplies water to the Mixed Bed Polishers after it passes through a degasifier The brine from the BWRO is returned to the SWRO feed The Mixed Bed Polishers effectively remove remaining anions, cations, and CO2 from the RO permeate, resulting in ultrapure water that is stored in the Demineralized Water Storage Tank.
The produced Demineralized water qualtity to be,
• Total Silica as SiO2 ≤ 0.01 ppm
The mixed bed polisher resin is regenerated on a weekly (168 hr) basis, using acid and caustic
The regenerated wastewater flows to chemical wastewater pond which is combined with UF cleaning chemical waste The combined chemical wastewater is transferred to Waste Water Plant
The potable water system utilizes potable water pumps to draw service water from the plant and fire water storage tank, which then passes through activated carbon filters designed to effectively remove organic contaminants.
The filter effluent is treated with sodium hypochlorite to maintain a residual chlorine level in the potable water tank The system operates based on the water level in the tank; the activated filter activates when water is needed and shuts off the service inlet valve to the activated carbon filter once the tank is full Periodically, the activated carbon filter undergoes backwashing using water from the plant and fire water storage tank, with the resulting wastewater directed to the chemical wastewater pond.
MAJOR EQUIPMENT DESCRIPTION
PRETREATMENT SYSTEM
The Raw water pretreatment system comprises of following major equipment:
The coagulant is dosed into the coagulation tank and the coagulant dosing system consists of following equipment:
A 38% ferric chloride solution will be utilized as the coagulant, delivered to the site and stored in the coagulant dosing tank The dosing will be adjusted based on the established rate determined from jar tests conducted on-site, ensuring optimal treatment of the feed water.
3.1.2 Polymer (Coagulant Aid) Dosing System
The polymer is dosed into the flocculation tank as a coagulant aid The Polymer Dosing System comprises of the following equipment:
Sodium hypochlorite will be dosed to maintain residual chlorine in the raw water Sodium hypochlorite dosing system comprises of the following equipment:
To lower the pH of raw seawater, hydrochloric acid (HCl) solution will be dosed into the system This acid is transported from a vertical storage tank with a capacity of 22 m³, which supplies acid for the entire plant, including applications for mixed bed regeneration and ultrafiltration (UF) cleaning.
The Clarified Water Pond, constructed from concrete and internally painted, serves as a reservoir for clarified water sourced from the Lamella Clarifier, supplying feed water to the UF feed pump Additionally, this pond is equipped with a Level Transmitter for monitoring water levels.
Ultrafiltration (UF) is a process that filters particles on the basis of size In membrane separations,
UF is typically used to separate or remove relatively large particles, such as microbes, bacteria, and macromolecules with molecular weights greater than approximately 300,000 Daltons or sizes greater than approximately 0.08 μm
The UF membrane filtration system is designed to effectively treat feed water with high suspended solids, ensuring it meets the quality standards required for reverse osmosis (RO) feed water This system features membrane modules mounted in a compact skid assembly, optimizing space and simplifying operation Constructed from polyvinylidene difluoride (PVDF), the membrane fibers offer excellent chemical and mechanical stability, enhancing the system's overall performance.
Clarified seawater is pumped through UF filters using UF Feed Pumps To safeguard the UF membrane fibers from large debris and inhibit crustacean growth, raw seawater is pre-screened with strainers that have a pore size of 120 μm or smaller This pre-screened water is subsequently directed to the UF membrane skids for further processing.
The UF membrane system operation consists of filtration, flushing, air scouring, Maintenance
Cleans (MC), Recovery Cleans (RC), and Membrane Integrity Test (MIT) are essential processes in filtration, where feed water is pressurized externally on the membrane fiber, facilitating its flow into the inner lumen in an outside-in configuration.
UF employs a dual flushing process for effective control, consisting of feed flushing and filtrate flushing The feed flushing is powered by the UF feed pump, while the cleaning pumps facilitate the filtrate flushing Cleaning water, sourced from filtered seawater in the filtered water pond, is utilized for this process Consequently, all cleaning wastewater is directed to the seawater waste pond, where it is combined with other seawater waste before being transferred to the outfall.
Cleaning pumps are essential for the effective cleaning of UF membranes, utilizing hydraulic and maintenance cleaning methods with chemicals These processes involve the use of UF cleaning pumps, sodium hypochlorite dosing pumps, and hydrochloric acid dosing pumps The cleaning cycle is automatically initiated by a PLC timer, which activates the system every 24 hours.
Air scouring blowers are essential for the effective air scour of UF membranes Each UF membrane module is equipped with air manifolds and a housing at the bottom, designed to efficiently deliver air.
UF air blowers This air provides shear to the membrance surface, dislodging debris, which is then flushed from the system
The above-ground Filtered Water Pond is designed to collect filtered water from the UF trains, supplying the necessary water for their cleaning Constructed from concrete, the interior of the pond is also painted to enhance its functionality and durability.
The Filtered Water Pond is equipped with a Level Transmitter, ensuring optimal water levels Additionally, the outlet header of the UF trains features a turbidity analyzer that monitors and indicates the quality of water entering the pond.
SWRO SYSTEM
The RO System for service water production comprises of following major equipment:
• 3 x 33% SWRO High Pressure (HP) Pump equipped with VFD
• 3 x 33% Energy Recovery Device (ERD) with booster pump with VFD
The water supplied to the SWRO trains is maintained at high pressure, with careful monitoring to ensure adequate suction pressure for the high-pressure (HP) pumps Additionally, specific installations will be implemented along the same line to enhance system efficiency.
• Pressure transmitter at both suction and discharge of HP pumps
• On/Off feed isolation valve to isolate all three trains
• Static mixer for antiscalant and sodium bisulfite
• On/Off dump valve to divert feed in case of ORP alarm which may indicate presence of chlorine residual in the feed water to the SWRO trains
RO membranes are sensitive to residual chlorine, necessitating the use of a de-chlorination chemical in feed water Sodium metabisulfite, in powdered form, serves as the effective de-chlorinating agent Upon mixing with water, it converts into sodium bisulfite solution (SBS) Due to the rapid nature of the dechlorination reaction, it is advisable to dose SBS upstream of RO cartridge filters for optimal performance.
SBS Dosing System comprises of the following equipment:
Chemical solution preparation will be conducted manually To manage any residual chlorine, a feed dump valve is installed after the cartridge filters on the RO feed water line, allowing diversion of water to the seawater waste pond Residual chlorine detection is ensured through two redundant instrumentation systems: the ORP monitor and the chlorine residual monitor.
Antiscalants are essential for preventing membrane scaling caused by exceeding solubility limits, particularly during the final stages of reverse osmosis (RO) processes By targeting the formation of salt nuclei, these chemicals effectively inhibit scaling, especially when calcium carbonate concentrations can reach four to five times higher than in the feed water An efficient antiscalant dosing system includes specialized equipment designed to ensure optimal performance and protect membranes from damage.
To safeguard SWRO membranes from small particulate matter, cartridge filters are utilized as the final line of defense These filters effectively shield the membranes from both suspended and non-suspended solids, ensuring optimal performance and longevity of the SWRO system.
4 x 33% capacity Cartridge Filter is provided in this plant, rated at 5 àm nominal particle size
These Cartridge Filters are provided with suitable vent and drain valves that are manually operated
Cartridge filters are equipped with a differential pressure transmitter that monitors the pressure difference between the inlet and outlet To ensure optimal performance, it is essential for the plant to implement a policy of replacing the cartridges every two to four weeks Additionally, if the differential pressure transmitter indicates a "high alarm setpoint" before the scheduled replacement, the cartridges must be changed immediately.
3.2.4 SWRO High Pressure (HP) Pumps with VFD
The SWRO high pressure pump provides the reverse osmosis pressure required to produce required permeate water quantity and quality as projected by the RO computer projection
Each SWRO train is equipped with a properly sized RO high-pressure pump, and variable frequency drives (VFDs) are installed for these pumps to effectively manage flow and pressure.
The SWRO membrane system will utilize a PLC to control the pumps, ensuring a consistent permeate flow that adapts to variations in feed water temperature and membrane age Notably, the SWRO high-pressure pump will be positioned away from the RO frame or trains, while the variable frequency drive (VFD) will be housed within the motor control center (MCC).
Reverse osmosis trains utilize thin film composite (TFC) membranes arranged in a single-stage array to generate the necessary permeate flow Each SWRO membrane assembly consists of 36 pressure vessels, with each vessel housing 7 membrane elements The complete RO train is organized in a frame to streamline installation, commissioning, operation, and maintenance processes.
The SWRO train consists of feed headers, a permeate header, and a reject header, with a concentrate control valve regulated by its own flow loop to ensure consistent recovery This control loop, in conjunction with a VFD-controlled pump, maintains a stable system recovery rate of 45%.
The SWRO train is equipped with pressure transmitters at the membrane feed, total concentrate, and total permeate headers A PLC continuously calculates the differential pressure between the feed and concentrate, triggering an alarm when the membranes require cleaning.
Flow indicating transmitters are provided at the permeate lines The flow monitoring of permeate will provide an indication
Each train permeate line will be equipped with a conductivity analyzer to monitor the conductivity of the produced water Additionally, a sample valve will be installed on each permeate line to identify any membrane malfunctions that may occur due to sudden increases in conductivity values.
The concentrate stream from SWRO Unit is connected directly to the seawater waste pond The
The SWRO permeate is directly channeled into the SWRO permeate tank, and based on the tank's water level, the permeate flow is subsequently directed to the plant and fire water storage tank according to its intended use.
3.2.6 Energy Recovery Device with Booster Pumps with VFD
The concentrate from each train of the SWRO system is directed to an energy recovery device, which effectively lowers the overall power consumption of the high-pressure pump motor for each train.
The energy recovery device will be based on isobaric technology The concentrate from the energy recovery device will discharged to the seawater waste pond
During a prolonged shutdown, the 1 st SWRO membranes will be flushed with SWRO permeate water Flushing pumps will be provided for flushing of the SWRO HP pumps, SWRO trains,
ERD system and the high pressure piping system The flushed water through the membrane will be discharged to a trench that will drain into the seawater waste pond
Two flushing pumps will be provided and will be suitably sized to flush one train at a time
Flusing valve will be interlocked with the feed valve
A Clean-in-Place (CIP) system will be installed for efficient membrane cleaning and will include a mechanism for delivering preservation solutions as needed This permanent installation is designed to chemically remove biological, particulate, or scale fouling from the membrane at regular intervals, ensuring the restoration of differential pressure to its clean or normal levels.
The system will be permanently sited The site of the system will be dedicated area of the RO building
A pH sensor will be in the cleaning loop to monitor the chemical quality The system will be piped to each bank of RO modules by fixed pipework
The CIP System for both SWRO and BWRO comprises of the following equipment:
BWRO SYSTEM
The BWRO System comprises of following major equipment:
• 3 x 50% BWRO High Pressure (HP) Pump equipped with VFD
SWRO Permeate tank is routed to BWRO Units as pretreatment systems of MBP units BWRO units are composed of two (2) BWRO feed pumps, two (2) BWRO cartridge filters, three (3)
BWRO HP pumps with VFDs, two (2) BWRO trains
3.3.1 BWRO High Pressure Pumps with VFD
Two (2) BWRO train is supplied with three (3) BWRO HP Pump sized adequately for the duty
The BWRO High Pressure Pump speed will be controlled by a variable frequency drive (VFD)
The PLC will be programmed to ensure a consistent permeate flow by controlling the pumps, regardless of variations in feed water temperature or the age of the membranes Additionally, the SWRO high-pressure pump will be positioned separately from the RO frame and membrane rack, with the variable frequency drive (VFD) installed in the motor control center (MCC).
The BWRO membrane assembly for each train features a two-stage configuration with a 3:2 array of membranes, comprising seven membrane elements per pressure vessel The complete reverse osmosis (RO) train is organized within a frame to streamline installation, commissioning, operation, and maintenance processes.
The BWRO train consists of feed headers, a permeate header, and a reject header To achieve a consistent recovery rate of 87%, the concentrate control valve operates through its dedicated flow loop, complemented by a VFD-controlled pump This integrated control system effectively maintains optimal performance throughout the process.
The BWRO train is equipped with pressure transmitters located at the membrane feed, total reject, and total permeate headers A PLC continuously calculates the differential pressure between the feed and reject, triggering an alarm when the membranes require cleaning.
Flow indicating transmitters are provided at each of the permeate lines on each stage of the
Monitoring the flow of permeate at each stage of the BWRO system is essential for identifying potential malfunctions Any irregularities in flow may indicate issues related to one or more membranes within that specific stage.
A conductivity analyzer will be installed at the common permeate header to monitor the conductivity of the water produced by the BWRO system Additionally, sample valves will be placed along each stage's permeate line to quickly identify any membrane malfunctions, indicated by sudden increases in conductivity values.
The reject stream from the BWRO unit is directly linked to the SWRO feed line, while the BWRO permeate is routed into the influent header of the Degasifier, previously referred to as the BWRO Permeate Tank, along with the plant and fire water storage tank.
A forced draft type of degasifier with air fans are provided to remove carbon dioxide from
BWRO permeate flows into a packing material bed, where carbon dioxide is driven to the top of the column by an upward current of clean, filtered air.
The basin is also considered as BWRO permeate tank.
MIXED BED POLISHER UNITS
Mixed Bed Polisher (MBP) System comprises of the following equipment:
• 1 x 100% Regeneration System with hot water tank
The Regeneration System comprises of the following equipment:
• 1 x 100% Acid Dosing Tank (shared with wastewater neutralization acid dosing tank)
• 2 x 100% Acid Dosing Pumps (shared with wastewater neutralization acid dosing pumps)
• 1 x 100% Caustic Dosing Tank (shared with wastewater neutralization caustic dosing tank)
• 2 x 100% Caustic Dosing Pumps (shared with wastewater neutralization caustic dosing pumps)
A set of MBP Feed Pumps (2 x 100%) is provided for MBP Feed
The mixed bed polisher (MBP) features two 100% vessels that utilize anion and cation mixed resins to effectively polish BWRO permeate, resulting in high-quality demineralized water suitable for boiler makeup Operating under a pressure of approximately 4 bars, the MBP efficiently transports the treated water to the demineralized water storage tank.
Mixed bed units undergo regeneration with dilute hydrochloric acid and sodium hydroxide approximately once a week This fully automatic regeneration process is triggered by a totalizer or when the effluent conductivity surpasses the high setpoint alarm.
POTABLE WATER SYSTEM
The Potable Water System utilizes carbon filtration and chlorine treatment on SWRO permeate, ensuring compliance with WHO guidelines and Vietnamese regulations for safe drinking water.
Potable Water System comprises of the following equipment:
Potable water from the treatment system is directed to a potable water storage tank from where it is distributed to the potable water distribution lines
Service water from plant & fire water storage tank passes through activated carbon filters (ACF) for color and odor removal Two (2) ACF – one operating and on standby – are provided
Sodium hypochlorite will be dosed to maintain residual chlorine in the potable water line
Sodium Hypochlorite Dosing System comprises of the following equipment:
The filling of chemical solution into the dosing tank is done manually.
CHEMICAL STORAGE
3.6.1 Acid Storage, Unloading / Transfer System
Acid Storage Tank of vertical cylindrical type are provided Acid is supplied by chemical delivery trucks
A single fume scrubber is utilized to eliminate humidity from the air within both tanks, ensuring optimal conditions Additionally, a service line is linked to the scrubber to effectively treat all acid emissions.
3.6.2 Caustic Storage, Unloading / Transfer System
The system features a vertical cylindrical Caustic Storage Tank designed to prevent crystallization of caustic by maintaining its temperature It is equipped with a flange immersion type heater, ensuring the caustic remains hot during cold weather conditions.
3.6.4 SBS, COAGULANT AID STORAGE, UNLOADING / TRANSFER SYSTEM
FINAL TREATMENT OF WASTE WATER FROM WTP
All the chemical waste generated in the Demineralization Plant is transferred to the Chemical
The Chemical Waste Water Pond is designed to effectively manage and neutralize waste produced during the regeneration of a Mixed system It is strategically connected through drain pipes that are installed within concrete trenches, ensuring proper containment and treatment of wastewater.
Bed Polisher Unit, MBP non-chemical waste, ACF backwash waste, BWRO brine, and RO CIP waste
The system comprises of the following equipment:
• 1 x 100% Chemical Waste Water Pond (below ground),
• 2 X 100% Chemical Waste Water Transfer Pumps,
• 2 x 100% Acid Dosing Pumps (shared with MBP regen acid dosing pumps)
• 2 x 100% Caustic Dosing Pumps (shared with MBP regen caustic dosing pumps)
When the chemical waste water is received in the chemical waste water pond, initiation of neutralization operation starts:
• The neutralization acid & caustic dosing pumps start
• The dosing of chemicals is initiated based on the pH reading from the pH Transmitter
• Wastewater recirculation start while acid / caustic addition takes place
Once the pH has reached acceptable value, the valve on the recirculation line closes and the discharge side valve opens and the waste is discharged to the sump
3.7.2 Disposal of Sea Water Waste
All the sea water waste generated in the Demineralization Plant is transferred to the Sea Water
The Sea Water Waste Water Pond is specifically designed to accommodate the disposal of seawater waste produced from various processes, including Auto Strainer backwash, SWRO brine, thickening, filter pressing, clarifying, and off-spec RO waste, as well as UF cleaning waste.
The system comprises of the following equipment:
• 1 x 100% Seawater Waste Pond (below ground),
Once seawater waste is collected and the pond reaches a high level, the transfer pump activates to discharge wastewater into the sump The pond's slope and drain pit facilitate the settling and accumulation of solids, which will be regularly removed by a potable pump to ensure proper maintenance.
OPERATION
The Water Treatment System consists of three subsystems:
Each system will be controlled and monitored from the local control rooms via the PLC panel with operator station Each system will have PLC panel with operator station
Appropriate interfaces between local control panel and the plant DCS will be provided
(hardwired & soft signals) The important status of the Water Treatment System will be monitored from the plant DCS
When raw seawater is accessible, it is directly pumped into the pre-treatment system using CW pumps This initiates the pre-treatment process, which includes the addition of various chemicals, such as acids, to ensure optimal water quality for subsequent treatment stages.
Hydrochloric acid (HCl) is added to the feed line before the inline static mixer to optimize pH levels for effective coagulation The static mixer guarantees thorough mixing of the acid prior to entering the clarifier Following this, the water continues into a shared feed channel that links the coagulation tank and flocculation tank, where sodium hypochlorite (NaOCl) is also introduced.
Coagulant (FeCl3) is added to the coagulation tank to eliminate dissolved iron and organic matter while enhancing particle size for efficient settling Water flows through a flash mixer and overflows into flocculation tanks, where a coagulant aid (Polymer) is introduced to help bind and form larger flocs from the colloidal particles.
In the water treatment process, water from the flocculation tanks is mixed using a paddle-type slow mixer before flowing into a common feed channel This water then gravitates into two clarifier basins, which feature inclined (lamella) plates for efficient separation Each basin is equipped with a sluice gate for isolation As the treated water enters the clarifier, it moves upward through the inclined plates, allowing the effluent to exit at the top while solids, or sludge, settle at the bottom due to gravity.
The sludge scraper operates continuously to remove precipitate from the floor of the clarifier, preventing sludge buildup This accumulated sludge is connected to two disposal pumps via pipelines, which transfer the sludge to a thickener for treatment Finally, the processed sludge is handled by a filter press.
Clarified water from the basins is collected into common channel where clarified water is piped into a common clarified water pond by gravity
Service: Removal of particulates using a clarification process and chemical aids Inlet Flow: 2 x 550 m 3 /h (Inst Max)
Thickened Sludge Transfer Pumps – Qty: 2 x 100%
Retention Times: Coagulation Tank: 5 minutes
Flocculation Tank: 20 minutes Chemical Dosing: Coagulant: 11.2 liters/hr
Polymer: 770 liters/hr Thickener hydraulic loading: 4 m 3 /m 2 /day
Transfer By: Gravity to clarified water pond
Pumps for sludge waste Next Process: Ultra Filtration System
UF feed pumps generate the necessary pressure to push feed water through the pre-screen and UF membranes at the designed flow rate This process involves forcing water through the fiber into the lumen using an outside-in flow path The resulting filtered water is then directed from the UF skid to a filtered water pond To minimize the accumulation of foulants on the membrane surface, the filtration duration is determined by projection results and fine-tuned according to operational experience.
Filtrate flow is continuously monitored using a flow transmitter on the feed line and regulated by a flow control valve If the flow exceeds the upper limit or drops below the lower limit for a specified duration, the system will automatically shut down and enter a fault state.
If the transmembrane pressure (TMP) exceeds the established threshold for a specified duration, the system will automatically shut down and enter a fault state To ensure filtrate quality, an effluent turbidity analyzer continuously monitors turbidity levels and notifies operators if they surpass acceptable limits.
Air Scouring: In order to maintain optimal performance and to prevent irreversible fouling, UF membranes require cleaning at regular intervals
Membrane aeration blowers deliver low-pressure air to the base of the membrane module for effective air scouring This process involves a systematic approach of air scouring, draining, and refilling to eliminate debris from the membrane surface, thereby enhancing its performance.
Regular maintenance cleaning is essential for optimizing the performance of UF membranes, as air scours alone cannot fully restore their permeability due to irreversible fouling from adsorption To effectively recover membrane performance, maintenance cleans are conducted at scheduled intervals, combining chemical soaking with air scouring While feed water may be used, filtrate from the filtered water pond is preferred for its lower suspended solids and chlorine demand The maintenance cleaning process utilizes hydrochloric acid (HCl) to remove inorganic scaling and sodium hypochlorite (NaOCl) to oxidize organic foulants After the maintenance clean, the waste is directed to a chemical waste pond and subsequently neutralized before disposal.
Maintenance cleans are scheduled at predefined intervals but can also be initiated by elevated transmembrane pressure (TMP), indicating high levels of suspended solids in the feed water Typically, these cleans are performed 1 to 2 times daily, with the frequency influenced by the quality of the feed water and specific operational conditions.
Recovery cleans are essential for maintaining membrane performance, conducted at intervals based on membrane efficiency and recovery performance These aggressive cleaning processes target foulants that regular methods, such as air scouring and maintenance cleans, may not eliminate The goal of recovery cleans is to restore the membranes' permeability to levels close to their original condition.
Recovery cleans involve a combination of intense air scouring and chemical backwashes, along with prolonged chemical soaking at higher concentrations Utilizing elevated temperatures can enhance the cleaning process The frequency of recovery cleans is tailored to specific site requirements, generally occurring monthly to semi-annually.
Service: Removal of particulates using a clarification process and chemical aids Inlet Flow: 572 m 3 /h (Inst Max, each)
Equipment: UF Feed Pumps – Qty: 3 x 50%
Retention Times: Filtered Water Pond: at least 20 minutes
Transfer By: Pumps to Filtered Water Pond for filtrate
Gravity drain to Waste water ponds for UF waste
Please find the typical deail UF cleaning procedure in Appendix A
During normal operation, recovery is monitored by flow transmitters at both the permeate and reject lines The reject control valve automatically adjusts recovery in response to changes in inlet water conditions A conductivity analyzer continuously checks the permeate conductivity; if it exceeds a preset threshold, the permeate dump valve opens after a time delay, allowing drainage until conductivity falls below the high alarm setpoint If conductivity does not return to acceptable levels, the unit will shut down and enter a flushing cycle.
The work exchanger type energy recovery device (ERD) effectively utilizes the residual pressure from the SWRO concentrate stream to enhance the supply pressure of filtered seawater To compensate for hydraulic losses within the membrane system and the ERD, a booster pump is employed, ensuring that the necessary influent pressure for the RO train is achieved.
DESCRIPTION OF CHEMICAL STORAGE & FILLING
The storage tanks serve to store hydrochloric acid (33%) and caustic solution (45%) used for water treatment plant (Pretreatment, RO, MBP, potable water and chemical waste neutralization systems)
Typcial chemical filling procedure shall be recommendded as followings,
1 Protective safety goggles face shield, protective suit, and rubber gloves must be worn when working on the equipment or manually pumping chemical solution
2 The chemicals supplier, before beginning the filling process requires the authorized user to give confirmation by his signature that release into a working plant will not constitute a danger and will witness the filling process upon completion
3 The storage tanks and pipework shall be checked at initial filling by carrying out successfully hydrostatic tests and checks with water
4 The filling into the storage tank shall be depending on the site condition; using own tank lorry pump or using transfer pump
5 The fillinig connection has to be identified for each chemical solution
6 The relative isolation valves shall be opened after connection accordingly, then the discharge pump to be turned on
7 Operator must check the level of storage tank and discharge pump to be turned off, then the relative valves to be closed out and hose to be disconnected
Note that food grade chemical is required for potable water treatment only and industrial grade chemical is recommended for others chemcial treatments.
INSTRUMENT AND CONTROLS
Typical instruments necessary for the safe and efficient operation of the plant will be provided as followings, however please refer to the Instrument List (NS2-YL00-P0GCF-120001) and Piping
& Instrument Diagram (NS2-XG02-P0GCF-120001) for the further details
1 Flow transmitter on inlet water supply for total amount of feed
2 Flow transmitter on product water of MBP for total amount of product
3 Level transmitter on each pond / storage tank
4 Turbidity analyzer upstream / downstream of a lamellar clarifier
5 Turbidity / pH analyzer downstream of UF system
6 pH / Cl2 / ORP / Conductivity / SDI analyzer upstream of SWRO
7 Flow transmitter at SWRO permeate and concentrate
8 pH / ORP / Conductivity analyzer upstream of BWRO
9 Flow transmitter at BWRO permeate and concentrate
10 Sodium / Silica / pH analyzer at common MBP product
The water treatment plant will be primarily controlled automatically by PLC The interface between the Master Plant Control System are through hardwired connection and redundant
MODBUS TCP/IP Important WTP process values are sent to the Plant DCS through MODBUS TCP/IP protocol over redundant serial links Refer to Control Configuration Diagram (NS2-
CODE AND STANDARD
The codes and standards applicable for these systems are as listed below:
2 American Society of Mechanical Engineers (ASME)
3 American National Standard Institute (ANSI)
4 American Society for Testing of Material (ASTM)
6 International Electro technical Commisson (IEC)
7 Instrument Society of America (ISA)
8 National Electrical Manufacturers Association (NEMA)
REFERENCE
1 NS2-XG02-P0GCF-120001 Piping & Instrument Diagram
2 NS2-XG08-P0GCF-120001 Process Flow Diagram & Mass Balance
3 NS2-CC07-P0GCF-120001 Calculation Sheet
4 NS2-XW03-P0GCF-120004 Design Criteria
5 NS2-XXXX-P0GCF-125002 Process Control Functional Description
6 NS2-YL00-P0GCF-120001 Instrument List
7 NS2-YF02-P0GCF-120001 Control Configuration Diagram
8 NS2-CQ02-P0GCF-120001 Operation & Maintenance Manual
APPENDIX A (TYPICAL) UF MEMBRANE CLEARING PROCEDURE
Step Transition - Feed pump speed adjustment 10 10 O O X X X X X X X R→S S S S
Step Transition - Valve positioning and blower speed adjustment 5 15 O→X O→X X→O X X→O X X X X S S S→R S
Step Transition - Blower speed adjustment and valve positioning 5 145 X X X O O X X X X S S R→S S
Step Transition - Feed pump speed adjustment 10 155 O X O X X X X X X S→R S S S
Sequence duration (s) 190 Notes: O=open valve R=Run pump
Sequence duration (min) 3.2 X=Closed Valve S=Stop Pump
Pump ramp-up/down speed: Average
Cumulative chem free waste volume (m3)
The system includes various components essential for efficient operation: the Feed (AV-01) directs the Filtrate (AV-05) to the Top Drain (AV-06) and Drain (AV-07), while the Air Scour (AV-03) enhances filtration Filtrate is managed to Drain (AV-08), and air is supplied for MIT (AV-04) The MC/RC Feed (AV-02) is supported by the Chemical Injection Feed Pump (P-1) and MC/RC Pump (P-2) Additionally, the Air Blower (B-1) and Chemical Dosing Pumps (DP-1/2/3) play critical roles in maintaining system efficiency.
Step Transition - Feed pump speed adjustment 10 10 0.00 0.00 O O X X X X X X X R→S S S S
Step Transition - Valve positioning and blower speed adjustment 5 15 0.00 0.00 O→X O→X X→O X X→O X X X X S S S→R S
Step Transition - Valve positioning and blower speed adjustment 5 145 10.26 0.00 X X X→O O→X O→X O→X X X→O X→O S S R→S S
Step Transition - RC pump and chemical pump speed adjustment 10 155 10.26 0.00 X X O X X X X O O S S→R S S→R
Step Transition - RC pump and chemical pump speed adjustment 10 465 33 10.26 0.09 0.09 X X O X X X X O O S R→S S R→S
Step Transition - Valve positioning and blower speed adjustment 5 1075 10.26 0.09 X X O X X→O X X X X S S S→R S
7 Air Scour and Pressurized Chemical Drain 10 1390 10.26 5.52 5.61 X X X O O X O X X S S R S
Step Transition - Valve positioning and blower speed adjustment 5 1395 10.26 5.61 X→O X X→O O→X O→X X→O O→X X X S S R→S S
Step Transition - Feed pump speed adjustment and valve positioning 10 1405 10.26 5.61 O X O X X O X X X S→R S S S
10 Chemical Rinse Air Scour and Drain 60 1565 6 16.22 5.61 X X X O O O X X X S S R S
Step Transition - Valve positioning and blower speed adjustment 5 1570 16.22 5.61 X→O X X→O O→X O→X O→X X X X→O S S R→S S
Step Transition - Feed pump speed adjustment 10 1485 16.66 5.61 O O X X X X X X X R S S S
Sequence duration (s) 1485 Notes: O=open valve R=run pump
Sequence duration (min) 25 X=closed valve S=stop pump