Location

Shuwaikh, Kuwait

Application

Potable water production

Construction

Doosan Heavy Industries & Construction

Capacity

350,400 m³/d (92.5 MGD)

End-user

Ministry of Electricity and Water (MEW)

Source

Seawater

Start-up

2011

background

The Shuwaikh seawater reverse osmosis (SWRO) plant is a large-scale desalination plant in the Persian Gulf. It is the first desalination plant in Kuwait to use RO technology for seawater treatment and also the world’s largest SWRO plant using dissolved air flotation (DAF) and pressurized inside-out ultrafiltration (UF) as pretreatment steps. The combination of DAF and UF was chosen to guarantee reliable plant operation as the seawater in the area is highly saline, rich in organic components and known for occasional harmful green algae blooms.

Together, DAF and UF can efficiently remove high concentrations of suspended solids (SS) and small-sized colloidal particulates. As a result, the high-quality RO feed water that is produced has a consistent silt density index (SDI) value of less than 3.0 at all times.

UF Performance

X-Flow UF performance chart

Scope of supply

5840 x Seaguard 40 UF membrane
20 x Skids

red tide events

The Shuwaikh SWRO site faces occasional red tide events that can last up to 10 days at a time, and green algae blooms. During such events, the combined DAF and UF pretreatment has proven successful in removing the increased number of particles caused by the abnormal growth of algae with turbidity levels of up to 31 NTU. The high turbidity of the seawater leads to a higher effluent turbidity from the DAF units, which can have negative effects on the UF performance. First, the increased number of particles and colloids can plug the membrane pores. Also, extracellular polymeric substances excreted from algae can lead to increased membrane fouling, which is difficult to remove with normal backwash.

During the red tide event in May 2012, only limited measures were necessary to guarantee reliable operation of the UF system and provide optimum pretreatment for the RO system. To control the high turbidity, coagulation of DAF was enhanced and chemically enhanced backwash (CEB) frequency of the UF system was increased. These two simple actions ensured a continuous supply of high-quality pretreated seawater to the SWRO system, thereby preventing production reductions or shutdown and ensuring a reliable supply of potable water to the city of Kuwait.


data logging

As an example of the UF performance, above the operating data from one UF skid in operation is shown before, during and after the red tide event (May 5-10, 2012). The blue line shows development in membrane permeability over time.

The orange line shows development of transmembrane pressure (TMP). The data confirms stable UF performance during the red tide event, which allowed continuous operation of the SWRO desalination plant.