Use of seawater advised for construction sector

28 June 2011

The possibilities of using seawater directly for earthwork and some other segments of construction ought to be studied in order to reduce the massive consumption of potable water in the industry, a Doha-based civil engineer has suggested...

“Seawater use in the construction industry is very limited presently on account of corrosion related problems,” Saad Haqqi Ahmed al-Joudi told the first seminar hosted by Qatar Green Building Council’s Water Interest Group (WIG) on Monday.

There is an increasing need to use seawater in the Gulf, in the light of the scarcity being experienced for potable water, the main source of which is energy intensive and polluting desalination plants.

“Options should be explored if seawater could be used more in construction by, for example, separating concrete structures - that are prone to be affected by salinity – with polythene,” he said.

There are other methods to reduce the use of potable water in construction, according to the Iraq-born al-Joudi, who has worked in Asia, South East Asia, Middle East and the Gulf for nearly three decades.

“The use of potable water in concrete mixing could be reduced through the use of plasticisers. If the water used to wash the concrete mixers and trucks is recycled it can be profitable for the operators of such plants and better for the environment.”

Concrete curing is yet another area in construction where lot of water is required. Water spraying and two of the popular techniques used.

“Curing compounds can replace water in this regard,” al-Joudi stated.

Cement blocks used for construction also require a large quantity of water for making and plastering them.

“There are lighter and cleaner options for cement blocks and these methods use very little water,” he said.

The human consumption of water at construction sites and labour camps was also touched upon by al-Joudi, the director of Commodore Qatar Contracting Company.

“Instead of disposing off the waste water after transporting them to dump sites, processes for recycling of this water in the sites itself should be encouraged,” he said while adding that some companies are already doing this.

One of the subsequent presentations dwelt on the same topic, with Gulf Contracting Company (GCC) operations manager Andrew Ford introducing Bionest wastewater solutions.

Elaborating on a Qatar first for eco-friendly wastewater treatment, he said how GCC is turning 1.4mn gallons of sewage from one of its labour camps into as much recycled water per month and saving about QR2.4mn a year.

At the core of the Bionest system is a submerged fixed film reactor using a ribbon-shaped non-biodegradable polymer media.

The whole treatment train consists of a settling tank, the bio-reactor with aeration and disinfection.

The biomass (good bacteria) develops and firmly attaches to both sides of the media. The major portion of the reactor is aerated through linear air pumps and fine bubble air diffusers, which provide ideal conditions for better treatment.

In the remaining portion of the Bionest reactor, a high level of dissolved oxygen assists the oxidation process, in a calmer environment, ensuring no solids will escape and the final effluent will be colourless and odourless.

To bring the treated effluent to a reuse quality, a final disinfection is required.

Chlorination, ultraviolet, or ozonation are among the options.

“We have not had to remove the sludge from the Bionest system in one of our camps housing 1,600 workers for the past 10 months, in contrast to the 10 times daily cleaning of the tanks earlier,” Ford pointed out while highlighting the efficiency of the system.

Bionest, represented by GCC in Qatar, also offers Oasis mobile wastewater treatment solution, housed in standard 40ft containers.

“The mobile unit is being deployed on a trial at Qatar University,” he said. There are three fully operational Bionest systems in Qatar.