The process and equipment covered by this scheme can satisfy to
produce water for domestic use or agricultural irrigation as
1.1 Production application: domestic drinking water and agriculture
1.2 System capacity: 200m³/d(25℃)
1.3 System recovery rate:40%
1.4 System configuration: pre-treatment, SWRO desalination unit
(with energy recovery device) and assisting units.
2. Technological Process
Seawater →feed water pump→multimedia filter→5μm security filter→1μm
security filter→HP pump→RO device(with energy recovery
device)→fresh water tank
3. pretreatment equipment
The multi-media filter is to remove suspended solids and colloid
particles in raw water. Coagulant is added by dosing pump before
raw water entering into multimedia filter. Then flocculus formed by
coagulant and colloids is removed through the filter, meeting the
requirements on RO feed water (SDI15﹤5, turbidity﹤1NTU).
This system comprises of 2 sets of FRP filter with
diameterφ1200*1850, and flow is 8-12m³/h. It is filled with refined
quartz sand and anthracite with the height 1000mm. Multimedia
filter is controlled by multi-way valve to automatically back
Bactericide is added into filter inlet pipes, and its dosage is
controlled within free chlorine 0.1-0.3mg/L.
When confirming coagulant types and dosage, it usually adds ferric
or polyaluminium chloride, as well as polyacrylamid. Coagulant
dosage is controlled within SDI<5 ( coagulant amount 5-10mg/L).
Adding reductant (sodium bisulfite) is to neutralize free chlorine,
and it is added in the front of security filter or before RO
system. Dosage is 2-3 times as much as free chlorine.
Adding anti-scalant is to prevent carbonate and sulfate from
scaling precipitation. It is added in the front of security filter
and its dosage is around 5mg/L.
4. SWRO system
RO system mainly consists of double grade security filter, HP pump,
SWRO membrane element, pressure pipe, and RO tank and connected
instruments. This system adopts 1st pass SWRO process, and production flow is 200m³/d.
To prevent the particles in raw water and pipes from entering into
HP pump and RO module, two security filters are selected one after
another as RO pre-treatment. Precision of 2 sets of filters is 5um
and 1um respectively. Under normal working conditions, filter
element should be changed in time when the pressure difference
between inlet and outlet of filter is above 1 bar. Filter structure
can allow to change filter element rapidly.
5. HP pump
The pressure difference is the working power of RO device. Raw
water is lifted by HP pump to the working pressure of RO, which is
usually 5.0~6.0Mpa, making RO process stably operate, namely to
overcome that seawater osmotic pressure, driving permeate water
molecule through RO membrane into fresh water flow.
Membrane module of this system employs world advanced TFC composite
membrane( “USA DOW”), which has high desalination rate and high
flux of SW30-400 with dimension 8″×40″ as follows:
effective area (㎡)
②Confirm of RO membranes
In order to reach the system recovery rate of around 40% , the
first stage is selected with three branches of pressure
vessels(each vessel containing four membrane elements), and the
second is selected with one branch pressure vessel containing four
membrane elements. There are sixteen membrane elements in the RO
(Ps: it is theoretically adopted 20membrane elements, but we take
customer’s cost, placing space, etc into account, it is also ok to
use 16 elements as long as system recovery rate up to 40%. )
7. Energy recovery device
iSave21 Pressure Exchanger devices actually includes energy
recovery part and booster pump. They’re made of a high purity,
aluminum oxide ceramic that’s corrosion-proof, three times more
abrasion-resistant than steel, and provides unmatched durability.
The simplicity and modularity of this design allows for optimum
scalability, quick startup, and no required maintenance. The
iSave21, can achieve greater than 95% energy recovery efficiency.