Water. Desalination + reuse
Issue link: https://fhpublishing.uberflip.com/i/513849
TECHNOLOGY May-June 2015 | Desalination & Water Reuse | 35 | Businesses that play a pivotal part in the economy of the Oman are under persistent threat from a microscopic organisms in the sea. Oman's Sohar Industrial Port Area (SIPA) is home to major petrochemical, iron and steel, methanol, and fertilizer plants, as well as three power stations. Since its inception in 2006 it has drawn some US$ 15 billion in investment and holds a strategic place in the future development of the Oman. As the sole water services provider at SIPA, Majis Industrial Services (Majis) too has a signifcant role in the economy of the sultanate. Algae: a tide of trouble Table 1. The tenfold higher concentration of Gonyaulax polygramma in the backwash water compared to the intake seawater was unprecedented. SIPA's industrial units require water for cooling and process purposes as well as potable water along with wastewater collection, treatment, and re-use for irrigation. To meet SIPA's demand for water services, Majis has two seawater pumping stations – one under construction – with a combined capacity of 700,000 m 3 /h. It has also two reverse osmosis desalination capabilities – RO1 and RO2 (see box Testing conditions). Since 2006, SIPA has had to address some of the most severe challenges on record arising from harmful algal blooms (HABs). Algal blooms – created by the proliferation of water-borne phytoplankton – have been observed for more than 30 years in the Sohar region of the Oman. Some of the algae involved are potentially lethal to fsh and other sealife. But with SIPA's emergence over the past decade as one of the sultanate's largest industrial parks, the algal blooms have become a signifcant economic threat to the industries there. Majis' records of algal bloom events began in 2008 when a severe algal wave – known in the Gulf region as the Red Tide – disrupted operations at SIPA resulting in huge economic loss. The Sohar refnery's Phytoplankton Seawater (cells/litre) Backwash (cells/litre) Cylindrotheca closterium 125,000 25,000 Pleurosigma normanii 25,000 Pleurosigma sp 25,000 Ceratium furca 25,000 Dinophysis caudate 25,000 Gonyaulax polygramma 5,637,500 53,125,000 Prorocentrum sigmoides 375,000 Protoperidinium steinii 25,000 Protoperidinium depressum 62,500 Total 5,825,000 55,000,000 own reverse osmosis desalination plant was shutdown for four months and all of the RO membranes had to be replaced. In 2011 and 2013 green algal blooms had a similar impact. SEvErE CHaLLENGES The intense Red Tide of 2008-9 was particularly signifcant as it forced the complete closure of industrial units and the loss in revenues was enormous. In September 2013 Majis experienced a severe jellyfsh attack which was followed by a green HAB event lasting almost six months until March 2014. This came in the middle of the period during which RO1 was scheduled to be commissioned. While the jellyfsh were up to 20 cm in diameter, through the pressure of sheer numbers, some breached the bar screens, but were captured by the band screens. Some were killed by mechanical action and chlorination and their subsequent decomposition resulted in the downstream self-cleaning flters (SCF) becoming clogged with a layer of fsh paste. This created a pressure drop across the SCF so the pressure at the inlet of the microfltration pre-treatment system feed pumps was insuffcient and caused the system to trip. _________ Khurram Shahid and abdullah al Sadi, Projects Department, Majis Industrial Services SAOC ___ The water services provider at the industrial port at Sohar in the Oman has learned the hard way, how to combat the seasonal algal wave that can grind vital reverse osmosis desalination and other water treatment to a halt. Despite unprecedented assaults the notorious Red Tide has been tamed. Case study call The Middle East Desalination Research Centre (MEDRC) is calling on the desalination industry worldwide to submit case studies that might be included in a guidance manual on marine algal blooms The manual will include "strategies and pretreatment methods, particularly in SWRO plants, to treat the increased suspended solids and organic loads associated with HABs," said MEDRC. Case studies from thermal as well as SWRO plants are required. MEDRC said the manual would include discussions on risk assessment frameworks to ensure drinking water safety is maintained in the face of a toxic marine HAB along with HAB management response plans. Don Anderson, Siobhan Boerlage, and Mike Dixon will edit the manual. People wishing to contribute should contact Kevin Price (mkevinprice@medrc.org) at MEDRC.