Integrated ultrafiltration and reverse osmosis desalination systems
An open architecture desalination system having a field of water desalination using porous micro filtration or ultrafiltration (MF or UF) membranes followed by high pressure reverse osmosis (RO) membranes for salt removal. A novel integrated system with a unique process flow allowing use of multiple UF and MF membrane configurations on same platform is also disclosed. Additionally, the systemutilizes a noble process flow to enable high efficiency operation of the MF and UF membranes thus reducing footprint, longer life of the membranes and reduced energy.
1. A novel desalination system comprising:
i. a first-stage pre-filtration segment and a second-stage microfiltration or ultrafiltration (MF/UF) segment, the first stage pre-filtration segment hydraulically coupled to the second-stage MF/UF segment, a first built-in buffer tank and a third-stage reverse osmosis (RO) membrane segment following the second-stage MF/UF segment, the first built-in buffer tank hydraulically coupled to the third-stage RO segment, a second built-in buffer tank following the third-stage RO segment, the second built-in buffer tank hydraulically coupled to the second-stage MF/UF segment and to the third-stage RO segment, and a programmable logic controller;
ii. the second-stage MF/UF segment comprises a membrane bank, wherein the membrane bank is an inside-out membrane bank, an outside-in membrane bank, or a cross-flow membrane bank, wherein the inside-out membrane bank, the outside-in membrane bank, and the cross-flow membrane bank are interchangeable within the second-stage MF/UF segment;
iii. the first built-in buffer tank stores MF/UF filtered water and the second built-in buffer tank stores RO concentrate, wherein the first built-in buffer tank has a volume capacity to feed the third-stage RO segment without interruptions when the second-stage MF/UF segment goes through a backflush process, wherein the second built-in buffer tank has a volume capacity to backflush the second-stage MF/UF segment;
iv. the first built-in buffer tank is hydraulically coupled to the second built-in buffer tank;
v. the first-stage pre-filtration segment comprises a sequential combination of a centrifugal separator followed by a screen filter component in order to remove settleable and suspended particles;
vi. a single pump drives the first-stage pre-filtration segment and the second-stage MF/UF segment with intra-stage differential pressure measurement across the centrifugal separator, the screen filter component and the second-stage MF/UF segment;
vii. the screen filter component in part (v) has two parallel screen filters with 3-way isolation valves to replace one of the two parallel screen filters without interrupting system operation.
2. The novel desalination system of claim 1 , further comprising a plurality of two-way valves, wherein, the programmable logic controller controls the plurality of two-way valves for process control of the inside-out membrane bank, the outside-in membrane bank, or the cross-flow membrane bank within the second-stage MF/UF segment.
3. The novel desalination system of claim 2 , further comprising an operating interface in communication with the programmable logic controller for selecting a membrane specific process flow through the plurality of two-way valves for the second-stage MF/UF segment.
4. The novel desalination system of claim 1 , wherein, a pump drives backflush, clean-in-place of the second-stage MF/UF segment, wherein the pump further drives flush and clean-in-place of the third-stage RO segment.
5. The novel desalination system of claim 1 , wherein the second built-in buffer tank is used for backflush and clean-in place of the second-stage MF/UF segment, wherein the second built-in buffer tank is further used for flush and clean-in-place of the third-stage RO segment.
6. The novel desalination system of claim 1 , wherein backflush of the second-stage MF/UF segment with RO concentrate produces a high salinity surge in the third-stage RO segment causing disruption of bacterial growth and reduction in biological fouling.
7. The novel desalination system of claim 6 , wherein the high salinity surge in the third-stage RO segment produces a reverse permeate flow to effect removal of scalants and foulants from a membrane surface of the third-stage RO segment and to effect reduced long-term fouling.