Water Journal : Water Journal April 2011
new products & services water APRIL 2011 159 loops and will ultimately evaluate water quantity and quality considerations in a single framework. For more information phone (02) 6201 5168 or go to www.ewatercrc.com.au. BAHRAIN'S WATER GARDEN CITY TO PROVIDE SUSTAINABLE SERVICES Bahrain is an archipelago of 40 islands in the Arabian Gulf midway between the Qatar peninsula and Saudi Arabia. On the north shore of the kingdom's capital city, Manama, a new mixed-used urban development aims to maximise the value of its key asset: water. Water Garden City incorporates luxurious marinas and beaches to create a premier seaside community in the heart of the Gulf's fast-growing financial district. Developer Albilad Real Estate is building the city on a 400-hectare site that has been reclaimed from the sea. Accommodating a potential population of 30,000 on land and another 10,000 afloat, the designers are challenged to provide ecologically sustainable infrastructure, including a gravity sewerage network. The design was cost-effectively achieved with the help of Bentley software. Scott Wilson, a global integrated design and engineering consultancy (now part of San Francisco-based URS Corporation) and lead consultant for the project, worked with sub-consultants to develop the master plan, which incorporates road corridors, building massing and land-side marina facilities, as well as a large-scale marina sculpture called The Pearl. Part of the land was previously reclaimed from the sea; for the remainder, Scott Wilson prepared specifications, carried out the tender evaluation, and supervised reclamation. Scott Wilson's engineers also completed conceptual designs for the Water Garden City project and are currently progressing with the preliminary infrastructure designs, including potable water, sewerage, storm water drainage, irrigation, district cooling, power, solid waste management, and telecommunications services. They used Bentley's SewerGEMS Sanitary, included in the SewerGEMS application for urban sanitary and combined sewer analysis and modeling to design the sewerage network for the project. The network design was submitted to the Ministry of Works, Sanitary Engineering Planning and Projects Directorate, and subsequently approved. The gravity sewer network proposed for the project included three intermediate sewage lifting stations. Minimum depth of manholes was assumed to be 1m, with the maximum depth of manhole limited to 5.5m to avoid dewatering problems during the installation of the sewer network and potential inflow of saline water during operation. Permissible velocities derived from the network modeling ranged from 0.6m per second (m/s) to 3m/s. "By using SewerGEMS, we achieved a savings of approximately 30 per cent to 40 per cent of the network design time compared to the previous design process using Excel spreadsheets," said Scott Wilson infrastructure design engineer Prasada Rao B.V.R.K. "Considerable time was also saved in developing the profiles of the sewer network. Thanks to SewerGEMS' ability to run directly within AutoCAD and MicroStation, we could generally achieve a 25 per cent savings in time spent in drawing production." BIO-CEL® MBR COMBINES THE BEST OF BOTH WORLDS The German-manufactured BIO-CEL composite membrane bioreactor (MBR) embodies the advantages of both capillary type MBRs and flat sheet designs, but without the disadvantages of each. The BIO-CEL, by virtue of its unique bonded composite polymer flat sheet membrane panel, is not only resistant to clogging and braiding with hair, but can be back-flushed under pressure using permeate in the same way as a capillary type membrane. Membrane Bioreactors (MBRs) have become recognised as a state-of-the-art wastewater treatment technology. With increasingly stringent discharge regulations and the desire to recover and reuse water wisely, they provide a safe and effective way to ensure a consistent high-quality effluent conforming to the required health standards. Most MBR plants today employ submerged type membrane systems where the surface of the membrane is directly exposed to plant MLSS. Dewatering occurs when a small negative pressure is applied to the filtrate side of the membrane wall, drawing clean water through the billions of microscopic membrane pores and leaving biomass behind. Biomass solids are cleared away by MLSS crosscurrent over the membrane surface, which is usually assisted by vigorous aeration turbulence. Submerged MBR systems basically fall into two categories: capillary tubular types including hollow fibre type systems; and flat sheet types which include the conventional rigid central permeate plate and outer frame type and the unique BIO-CEL semi rigid composite laminated structure membrane, which brings us to the question; which type is better? Capillary tube type MBR systems offer a high packing density and a smaller footprint for a given membrane surface area. Aeration scouring is usually coarse bubbles emanating from the centre of a bunch of membrane fibres. This type of membrane offers good performance but is prone to silting and braiding by hair which is almost impossible to remove. Efficient inlet screening helps but doesn't eliminate the problem. Capillary type membranes usually incorporate a reverse backwash cycle using permeate water to control pore fouling and maintain good flux rates. Standard plate and frame flat sheet type MBR modules offer good filtration performance and are not affected by silting and braiding. Plate and frame type flat sheet membrane packing density is much lower than capillary type membranes and low flow velocities at the membrane plate fixing ends can lead to blockages. Plate and frame type flat sheet membranes cannot be back- flushed using pressurised permeate. Developed by Microdyn-Nadir, a German company with over 40 years' experience manufacturing membrane filtration products, the patented BIO- CEL MBR module offers the best of both and more. The key to the BIO-CEL's performance is the unique bonded composite polymer membrane panel structure. Panels are Sewerage gravity network designed in SewerGEMS. The German-manufactured BIO-CEL composite membrane bioreactor.
Water Journal March 2011
Water Journal May 2011