Archives: Case Study

Introduction  

The town of Ruwais lies 250km west of Abu Dhabi, the capital of UAE where the largest oil well fields and petrochemical industrial complex are located.

The successful operation of this entire complex is managed by Abu Dhabi National Oil Company’s (ADNOC) professional and dedicated workforce. ADNOC has constructed a township providing the most modern amenities for all its employees and other associated companies. The township is named Ruwais Housing Complex.

ADNOC plans for continued growth necessitated the expansion of the present township. While conforming to its commitment to maintain the highest standards of environmental protection, and its augmentation of the township’s infrastructure was part of this planned work. This included expansion of the drinking water supply and a modern wastewater treatment plant.

Metito was awarded the multi-million US Dollar utilities expansion project against tough competitive bidding. Project execution involved complying with the international standards, as well as the specifications drawn by ADNOC and its consultants CRSS International. Metito successfully completed this most challenging task to the entire satisfaction of the project owners.

Scope of Work 

This included the detailed engineering, manufacture, inspection, supply, installation, testing and commissioning, start-up, performance test and training of personnel at site.

Plant General Information                                                        

The drinking water and wastewater treatment facilities are extensive and mainly comprise the following units:

• Drinking water treatment, storage and pumping
• Sewage pumping stations
• Sewage treatment plant
• Sludge digestion & handling facilities
• Irrigation pump station
• Electrical and control equipment
• SCADA System
• Miscellaneous site works

Plant Technical Characteristics

Drinking Water Treatment, Storage and Pumping

Drinking water from the main water supply line is stored in two 20,000 US gallons capacity storage tanks. A fully automatic chlorination system renders water suitable for drinking purposes. The disinfected water is delivered to the housing complex through a set of transfer pumps. The minimum water supply pressure is maintained through the use of two 129m³ hydro-pneumatic tanks. The tanks are in carbon steel construction and designed as ASME (U) STAMPED pressure vessels. All associated compressors, controls and monitoring devices are designed for fully automatic operation.

Sewage Pumping Stations

Raw sewage from the housing complex is transferred to a main sewage lift station through two intermediate pumping stations from the plant located at distances of about three and five kilometers. Each intermediate pumping station is provided with two sewage lifting pumps, each having a capacity of up to 100 m³/h. From the main sewage lift station. sewage is pumped to the wastewater treatment plant. Four pumps transfer the sewage to the treatment site. The pump capacities vary from 260m³/h to 560m³/h. The lift station equipment is installed about 11 m below ground, and the dry well is furnished with advanced ventilation and odour control equipment.

Wastewater Treatment Plant

This includes the following units:

• Raw sewage metering station
• Inlet headworks
• Aeration tanks
• Clarifiers
• Secondary coagulation, flocculation and settlement
• Travelling bridge gravity filters
• Sludge digestion and handling
• Gas chlorinating equipment
• Effluent pumping station
• Irrigation pumping station

Inlet Headworks

The inlet headworks comprise grit removal and disposal facilities to remove the heavy grit particles, followed by automatic and manual screens that remove large floating and suspended objects from raw sewage.

Aeration Tanks

Partially treated raw sewage enters two circular aeration tanks 44m in diameter. To achieve economy, the tanks are constructed as earthen basins with waterproof liners. The integrity of the liners is continuously monitored through a uniquely designed leak detection grid installed under each liner. Each aeration tank is combined with an anoxic zone for effective de-nitrification. Two 75kW Brush Rotors are installed in each basin to meet the aeration requirements.

Clarifiers

The aerated sewage passes through two circular clarifiers 13.5m in diameter. The effluent flows through a peripheral inlet and central collection system, and the clarifiers are equipped with gear-driven central cage and rake mechanism. Sludge is raked into a central cone at the bottom of the clarifier. The pipework is arranged to provide continuous sludge re-circulation and excess sludge discharge.

Secondary Coagulation, Flocculation and Settlement

Biologically stabilised treated waste is further treated by a coagulation and flocculation process, and fine suspended solids are again removed by the sedimentation process with the help of two 5Om x 5Om x 4.5m deep settlement tanks. Like the aeration tanks, these tanks are also designed as earthen basins with waterproof liners and continuous monitoring leak detection.

Travelling Bridge Gravity Filters

Clarified water is treated in the gravity filters to further improve the quality of water. The filters are provided with traveling bridge backwash equipment mounted on a frame structure that moves along the filter via a mechanism powered by a reversing motor. The backwash equipment. comprising a moving stainless steel hood and the submersible pump is mounted on this bridge. Hydraulically sized orifices are provided to collect the backwash water  uniformly.

Sludge Digestion and Handling

Sludge from the biological and clarifier stages is pumped to two 1,150 m³ digester tanks, where it is digested and stabilised under aerobic conditions. Two centrifugal air blowers, each having a capacity of 3,300 m³/hr, supply the required air. Digested sludge is pumped to a circular sludge thickener 15m in diameter, from which thickened sludge is pumped to the sludge drying beds. Underflow from the sludge drying beds and supernatant water from the sludge thickener is returned to the inlet headworks for recovery.”

Gas Chlorinating Equipment

The complete chlorination equipment is housed in a separate building. Two wall-mounted, vacuum-operated, solution feed, sonic flow type gas chlorinators are supplied to provide chlorine solution to the chlorine contact tank and filters. An automatic switchover facility ensures the continuous supply of chlorine, and the gas feed flow is controlled automatically. Ancillary equipment installed include an on-line chlorine analyzer, chlorine leak detection and gas monitoring and chlorine emergency kit.

Irrigation Pumping Station

The irrigation reservoir receives treated water from the wastewater treatment plant for storage and distribution. The reservoir is provided with inlet control valves and four sets of pumps to supply water to the irrigation system. The water passes through online automatic self-cleaning filters and a hydro-pneumatic tank to maintain minimum pressure in the system.

Electrical and Control Equipment

These include state of the art SCADA, process control panels, MCC’s, cabling, wiring, earthing, plant and street lighting and lightening protection. An ATS/MTS with bypass facility is provided to avoid parallel operation of main and generator incomers to the MCC in line with the latest Water and Electricity Department (WED) requirements. PLC based control panels are located near the individual plant facilities. These are water supply system and other facilities. All control stations are connected to the SCADA system over a multi drop communication link. The SCADA system operates on a dedicated digital leased line to provide continuous information. Drinking water is received from Ruwais refinery located 25km away, and the SCADA system transmits the necessary information to the refinery for an assured supply of drinking water to the housing complex. The link between the two locations is maintained by a fiber optic communication network.

The entire water treatment package was successfully commissioned and put into operation to the full satisfaction of ADNOC. The project is a clear demonstration of Metito’s commitment to provide its clients with the most advanced treatment technologies whilst meeting the most stringent international and local standards.

Introduction

The Egyptian economy experienced a massive growth in the early part of 2003, resulting in an increase in demand for electric power. As part of its utilities’ expansion plan, the Egyptian government decided to construct a new power station at Nubaria, the township located 120km north-west of Cairo, and awarded the project to Metito. The project was designed to utilise Egypt’s abundant natural gas resources and high- efficiency turbines which are characterized by their low carbon dioxide emissions.

As part of the project, Metito constructed several water and wastewater treatment plants to cover the entire scope of water treatment requirements for the site.

Scope of Work

Metito was in charge of the design and erection of the complete electromechanical works for the water and wastewater treatment plant package, including:

• Nile River intake chlorination utilizing sodium hypochlorite shock dosing
• Raw water pre-treatment system incorporating solid contact clarifies followed by dual media filters to provide 225m³/h for process water and 40m³/h for potable uses
• Potable water system utilizing activated carbon media filtration and disinfection
• Ion exchange demineralization plant comprising 3 streams of skid-mounted activated carbon polishing filters, clarification exchangers, degassers, anion exchange columns and mixed bed vessels, producing 1500m³/h per stream
• Chemical wastewater neutralization for waste generation
• Wastewater treatment package that includes; clarification, filtration and neutralization
• Oil separation package to cater for 100m³/h of oily water separation through an API separator and DAF units
• Sanitary sewage treatment package to handle a daily flow of 400m³/day
• Sludge dewatering system utilizing two sludge thickeners and filter presses
• Five chemical injection systems for steam turbine units to control biological growth, condition the water for the condensate system, deaerator, heat recovery boiler drums and circulating water
• Turbine steam and water analysis systems comprising two analyzer shelters each housing sample conditioning equipment, instrumentation, probes, analyzers, racks and cabinets
• Fully automated SCADA work stations

Key Benefits

• A total solution for the power plant water and wastewater treatment needs
• Efficient design that takes into consideration the stringent requirements of the owner and the project manager
• Client ease of mind with all requirements handled by one contractor; Metito
• Novel technology and reliable design that meant trouble free operation
• Technologies with minimal carbon footprint and the use of low carbon emission equipment therefore minimal environmental impact
• Timely execution of the water and wastewater treatment plant package which was imperative for the start-up of power plant
• Full local support from a well-established company with local presence and global knowhow, guaranteeing world-class quality deliverables

Introduction

National Fertilizer Public Company Ltd. of Thailand (NFC) constructed a modern NPK fertilizer plant, that included a Phosphoric Acid manufacturing unit, within the complex. As a natural result, the wastewater had an abnormally high content of various highly toxic pollutants like Phosphoric Acid & Fluorides coupled with Sulphates. The characteristics of this wastewater and the amount of waste to be treated, coupled with the strict environmental discharge regulations, required a tailor-made water management solution, and special treatment processes.

Due to the nature of the project and to such stringent requirements set by NFC, Metito was chosen and entrusted to execute the wastewater plant and other water treatment facilities. The plant was then classified as one of a few of its kind in the world.

Scope of Work         

Metito took charge of the complete design, engineering, manufacture, inspection, testing and supply on FOB basis, supervision of installation & commissioning, start-up and performance testing for the complete water and wastewater treatment plant packages. The packages included;

• Process Wastewater Treatment Plant with a capacity of 100m³/hr to treat waste streams from the various production units. The plant units include a Hastelloy-C heat exchanger, a 1200m³ Acidic water-lined equalisation basin, automatic lime handling and dosing system, two lime silos each measuring 6.5m diameter and 31m high, pre-contact tanks, 15m diameter primary and secondary clarifiers, and belt press sludge thickeners with polymer dosing units
• Water Pretreatment System treating 310m³/h of raw water for process use, through solid contact clarifiers
• 20m³/h Ion Exchange Demineralisation Plant in two streams with anion and cation columns
• Ion Exchange Plant Chemical Waste Treatment Collection and Treatment System
• 168m³/day Extended Aeration Sanitary Drainage and Treatment System
• Distributed Control System for controlling all plant operation

Key Benefits                            

• A total solution for the fertilizer plant water and wastewater treatment needs
• An optimum design that takes into consideration the stringent requirements set by the owner and the project consultants
• More efficient project management since all packages are handled by one contractor: Metito
• An efficient wastewater treatment plant that takes into consideration the tough and varying quality of the feed waste with a practical Zero Liquid Discharge (ZLD)
• A reliable design that meant trouble-free operation and minimum downtime
• Full local support and customer service, in a world-class quality, from a well- established company

Introduction

Sousa is a touristic city located on the south Mediterranean coast. It is home to several beach resorts that are flocked by thousands of tourists every year. The city constitutes one of the major income inducing areas for the Tunisian government, and such the Tunisian government decided to establish a new water treatment plant. The new plant has a capacity of 26,000m³/day for potable use, and can accommodate the increasing demand for the water in this busy area.

The client, SONEDE (Societe Nationale d’Exploitation et de Distribution des Eaux), tendered the project on an urgent basis in a bid to meet the anticipated increase in demand which was expected in the summer of 2004. Metito was entrusted by SONEDE to execute and deliver the plant within 4months from date of award. The project encompassed the complete design, manufacturing, installation and commissioning of the plant, followed by two months performance reliability test. Classroom and field training of client personnel were also part of the services rendered under this contract.

Scope of Work

Metito’s responsibility included the design and supply of the following electromechanical process equipment, arranged in 3 streams:

• Prechlorination system utilizing two sodium hypochlorite injection systems
• Coagulation and flocculation systems utilising alum and polymers
• 3 flash mixing tanks
• 3 flocculation tanks
• Packaged prefabricated steel tube settler clarifiers
• 3 break tanks
• Filter feed and backwash pumps
• 3 automatic dual media multi-compartment filter vessels
• PLC controls with Man-Machine interface

Key Benefits

• A total solution that accommodates the water needs at Sousa
• Prompt support for seasonal requirements
• Timely execution without compromising quality or the capacity required to kick off the project, which were both imperative for the project
• A packaged plant that could be easily and quickly deployed
• A reliable design that meant trouble free automatic operation and minimum downtime
• Full local support, and customer service, in a world-class quality, from a well established company

Introduction

Under the visionary leadership of Sheikh Mohamed Bin Rashid Al Maktoum vice president and prime minister of UAE and Ruler of Dubai, Palm Jumeirah township was inaugurated as an iconic project constructed off the coast of the emirate of Dubai. The project was built in the shape of a palm and has extended the stretch of Dubai coastline by more than 120 km. As Palm Jumeirah is the only modern structure seen from space, so is Metito’s on-site sewage treatment plant achieving many firsts.

Being host to some of the world’s renowned dignitaries and celebrities meant that all associated utilities demanded challenging innovations, adherence, and commitment to maintaining the highest standards of environmental protection and architectural aesthetics. The location of the plant on prime land left extremely limited space for plant buildings and respective facilities. Architecturally, the treatment plant is inside a circular building constructed below ground to keep it invisible. The given geometry, limited space and underground conditions presented a very difficult task of arranging the equipment, facilities, and utilities. Metito employed the MBR (membrane bio-reactor) process technology which is the latest technology in treating waste. This process requires a considerably reduced footprint than other conventional schemes and has the added advantage of producing high-quality treated water.

Special designs were adopted for an approach to allow operational access and equipment maintenance. Limited headroom dictated the use of a specially designed serpentine monorail that covers the whole workspace. The status of the location demanded zero tolerance for any unpleasant odor emissions.

The ventilation system, dehumidifier and odor control units in the workspace were carefully designed taking into consideration these stringent demands.

Scope of Work

This included the detailed engineering, manufacture, inspection, supply, storage, installation, testing and commissioning, start-up, performance test and training of personnel at site. It also included operation and maintenance of the plant for eight years.

Plant General Information

The sewage treatment facility mainly comprises the following units:

• Inlet-works
• Biological treatment
• Sludge handling
• Chemical cleaning
• Electrical and control system

Plant Technical Characteristics

Raw sewage from the residential community is transferred to a main sewage lift station through two intermediate pumping stations.

The sewage treatment plant is designed to treat 18,000 m³/day of domestic sewage. The collected raw sewage is received through a 600 mm diameter underground main, and the incoming flow is metered before it enters the treatment units.

Plant Data Summary

Average daily flow	18.000 m3/day
Peak daily design flow	21.700 m3/day
Peak factor	2.5
Peak hourly flow	1875 m3/hr
Peak flow duration	2 hours

Influent Analysis

Temperature	22 -35	0C
BOD5	250	mg/l
COD	500	mg/l
TKN	55	mg/l
Assumed biodegradable TKN	50	mg/l
Suspended solids	250	mg/l
Phosphates	8	mg/l
Alkalinity	Min. 210	mg/l
Oil & Grease	< 40	mg/l
pH	6 – 9
Ammonia nitrogen	35	mg/l
Ambient Temperature	10 minimum 50 maximum	0C 0C

 Treated Water Quality

BOD	< 10	mg/l
COD	< 50	mg/l
TKN	< 5	mg/l
Suspended Solids	< 10	mg/l
Ammonia – Nitrogen NH3(N)	< 3	mg/l
Total Nitroge (TN)	< 30	mg/l
Fecal Coliform	< 10	mg/l

Process Description

Inlet Works

Metered raw sewage from the mains is released into a concrete channel through two 3mm perforated plate fine screens operating on a duty/standby basis. While screenings are removed, the screen surface is cleaned by spray nozzles as the basket is rotates. For clean and easy handling, the collected waste from the screens is compacted and dewatered up to 40% w/w. A Vortex type grit removal system with grit classifier is installed after the screens to remove heavy grit particles.

Partially treated raw sewage enters two compartment equalization tanks The tank is constantly purged with enough air to maintain the sewage in agitation and prevent it turning septic.

Downstream membrane treatment is divided into six process trains to cater for plant turndown and to provide flexibility in operation. The common pump sump has six duty/ six standby feed pumps dedicated to transfer sewage to the Anoxic tanks.

The biological treatment of each process train comprises the following process units:

Anoxic Tank

The anoxic tank receives partially pretreated equalized sewage that has been intimately mixed with recycled flow from the anoxic recycle pumps. The returned flows contain nitrate due to the nitrification of ammonia in the membrane tank. Bacteria utilize the soluble and particulate COD in the incoming sewage to effect de-nitrification under anoxic conditions. Submerged mixers in each anoxic tank keep the bacteria in suspension and homogenously mixed with the soluble nitrate.

Aeration Tank

Sewage from the anoxic tanks passes to the aeration tanks by gravity. The aeration tanks provide an aerobic environment to ensure nitrification of ammonia and oxidation of BOD achieved by the provision of high efficiency fine bubble diffused aeration. The air supply to the diffuser system is monitored and controlled automatically to maintain optimum residual dissolved oxygen (DO) concentration in the tanks.

Membrane Bioreactor Tanks

Six membrane bioreactor tanks serve the function secondary aeration tank, whilst also assisting in the provision of air for the biological degradation processes. Each membrane tank contains 12 membrane units arranged in a double-deck configuration. To prevent surface, fouling, and membranes are continuously scoured by air supplied through diffused air pipe distributors below the membrane block.

Provision was made to chemically clean the membranes, if and when required. A diffuser flushing system is used to periodically flux the coarse bubble diffusers. Flux rate control is a critical operational feature hence flow through the membranes is controlled by modulating the permeate control valve to required flowrate through the flow meter on the permeate line.

Recycle Pump Control

The recycle pumps are subjected to intermittent operation to ensure a maximum recycle rate it low flow conditions. Intermittent operation is set according to the pre- determined schedule by a PLC.

Disinfection

The membrane process removes a large portion of bacteria from the sewage. Chlorination using sodium hypochlorite is imparted into treated streams to remove or inactivate any pathogenic bacteria that may grow in the tanks.

Sludge Digestion and Handling

Biological sludge is pumped to sludge digesters where it is digested and stabilized under aerobic conditions. Digested sludge is pumped to a dewatering centrifuge to produce sludge of 20 – 25% dryness. Concentrate from the centrifuge is returned to the plant inlet for recovery.

Electrical and Control Equipment

This includes state of an art SCADA system, PLC control panels, and MCCs. SCADA is implemented with a graphical depiction of the process as well as the graphical representation of process parameters and plant data that is also archived and retrievable. Power to the STP plant is fed from the facility substation which is equipped with dual incomers mains supply from DEWA as well as emergency supply from a generator. The design of the control equipment has taken into consideration the necessity for separate and independent operation of the MBR streams. so that failures in the control equipment associated with one stream will result in the shutdown of the affected stream only.

Project execution involved complying with the international standards and specifications drawn by the consultants. Important factors such as availability of plant, efficient use of manpower, high reliability and simplicity of maintenance have been considered in the design. The plant utilized minimum space whilst maintaining the overall architectural requirements. Technically, it provided a modern up to date process that ensures consistent water treatment quality. Metito completed this most challenging task to the entire satisfaction of the owner, and the successful operation of this entire complex was subsequently managed by Metito’s workforce.

Introduction

To cater for the increasing demand for power and for the surge in industrial needs, the Electricity Generating Authority of Thailand (EGAT) decided to build stage II of the South Bangkok Combined Cycle Power Plant to produce an additional 744 MW of power. The multi-million dollar contract was directly awarded by EGAT to Metito against international competition. The project demanded execution to the most stringent requirements laid down by EGAT and their consultants Black and Veatch International, Kansas City and Sindhu Pulsirivong Consultants, Bangkok. The complete works including the performance guarantee tests had to be executed within the jurisdiction of ASME codes, and the project had to be completed within a critical time frame. Metito took on the challenge, and fully performed to the satisfaction of the respective authorities.

Scope of Work

The scope included the complete design, engineering, manufacture, supply, inspection and testing, fabrication, installation, commissioning and performance test of the water and wastewater treatment packages which comprise the following:

• Circulating water make-up treatment system utilising four automatic cyclone separators to treat a flow of 3780 m³/h. The system clarifies water from the Chao Phraya river, where suspended solids level varies widely due to strong tidal influences
• Ion exchange demineralization plant for cycle make-up system with a capacity of 147.6m³/h, including activated carbon filters, primary cation exchangers, forced draft degasser, primary anion exchangers and a mixed bed polisher, all in two 50% streams
• Chemical waste collection and treatment system operating on a 600 m³ batch treatment principle
• 90 m³/day extended aeration sanitary drainage & treatment system
• Auxiliary water supply units – 150 m³/h each
• Miscellaneous mechanical and architectural services along with HVAC, lighting, fire protection and communication systems
• DCIS based complete control systems for overall plant operation

Key Benefits

• A total solution for the power plant water and wastewater treatment needs
• An efficient design that takes into consideration the stringent requirements laid down by the owner and the project manager
• Client ease of mind since all packages are handled by one contractor, Metito
• A reliable plant that takes into consideration the varying quality of the feedwater
• A safe proof design that meant trouble free operation and minimum downtime
• Timely execution which was imperative for startup of the power plant
• Full local support from a well established company with ‘’Local Presence and Global Knowhow’’