Desalination & Industrial Water Conditions & Solutions

gradient of precision

material and structural preliminary screening

Seawater Desalination Conditions

Open Seawater Intake: Normal Season

• Conditions: Seawater contains sand, shell fragments, algae, and organic matter; load varies with tides.
• Issues: Fine filter cartridges handle the main solid removal task, clogging within hours; marine organisms enter subsequent equipment.
• Identification: Online turbidity, chlorophyll, TSS, particle size, SDI15 trends with tidal patterns.
• Solution: Intake grates/screens → Coagulation/DAF or multi-media → 10–20 µm protection → 5 µm absolute-grade RO cartridge guard filtration.
• Accuracy / Structure: Grate 1–10 mm; coarse filter 50–200 µm; guard 10 → 5 µm.
• Materials: Seawater side PP/PVDF/FRP or seawater-resistant metal; filter cartridges PP/Nylon.
• Acceptance: SDI, turbidity, filter ΔP, and replacement cycle before RO.
• Boundaries: 5 µm filter cartridges serve as a safety barrier and should not receive high solid load from the original water.

Storm-Induced High Turbidity Seawater

• Condition: Sudden increase in mud, clay, and colloids.
• Issue: Multi-medium breakthrough, rapid pressure rise in cartridge guard filters; risk to high-pressure pumps from particulate matter.
• Identification: Raw water/filtrate turbidity, SDI, particle size, aluminum/iron and coagulant dosage.
• Solution: reduce flux → coagulation-sedimentation/DAF → multimedia or ultrafiltration → 20/10 µm protection → 5 µm absolute-rated filtration.
• Accuracy / Structure: 20→10→5 µm grading; final grade 5 µm absolute.
• Materials: High-capacity PP depth + pleated PP; housing resistant to seawater.
• Acceptance: Filters maintain planned cycle; turbidity/SDI before RO restored.
• Boundary: If cartridge changes are frequent within 1–3 months, check pre-treatment first, not to add more filters.

Beach Wells/Underground Water Extraction

• Operating Conditions: Turbidity is low, but may contain iron, manganese, sulfides, and fine sand.
• Issue: After aeration, iron and manganese oxidize and precipitate, forming deposits in the cartridge guard filter and before the RO.
• Identification: Dissolved/Total Iron and Manganese, ORP, Oxygen, Particle Size, SDI, and well pump start/stop.
• Solution: Gas stripping/oxidation precipitation based on water quality → 10 µm → 5 µm Absolute Grade; low colloids can simplify large-scale pretreatment.
• Accuracy / Structure: 10 µm protection
• Materials: PP filter; wet parts designed for chloride ion and corrosion.
• Acceptance: Filter color, iron and manganese, ΔP, SDI of RO feedwater.
• Boundary: Low turbidity does not equate to no scaling or iron contamination.

Final Cartridge Guard Filtration Before SWRO

• Operating Conditions: Completed conventional or membrane pretreatment, entering the high-pressure pump.
• Issue: Fragments from pretreatment, corrosion products from pipes, or resin particles entering the RO.
• Identification: Measure Turbidity before RO, SDI, Particles, and Filter Cartridge ΔP; Inspect the Filter Cartridge for Contaminants Upon Disassembly.
• Solution: 10 µm can serve as upstream protection; final 5 µm absolute grade, with pressure gauge/differential pressure transmitter interlocked.
• Accuracy / Structure: <10 µm is the lowest; recommend 5 µm absolute grade.
• Material: Synthetic non-degradable PP/Nylon; no fiber shedding.
• Acceptance: Clean ΔP, final ΔP, single cartridge flow rate, and replacement cycle.
• Limitations: While backwashing is possible, it is not suitable as the sole final safety filter.

Industrial Circulating Water, Boilers, and Reclaimed Water

Side Stream Filtration for Cooling Towers

• Condition: The circulating water contains 1–50 µm corrosion products, dust, and biological debris.
• Issue: Heat exchanger fouling; high differential pressure and energy consumption with full flow fine filtration.
• Identification: TSS, turbidity, particle size, iron, bypass ratio, and blowdown volume.
• Solution: Take a recirculation stream from 3–10% bypass → 50–100 µm for backwashing coarse filtration → 10–25 µm polishing; use pleated filters for low solids content.
• Accuracy / Structure: 50–100 µm coarse; 10–25 µm fine.
• Material: Backwashing sand filter/disk type/metal mesh; use pleated PP for small systems.
• Acceptance: Turbidity, heat exchanger differential pressure, blowdown and makeup water volume.
• Limitations: Pleated filters cannot replace microbiological control and water chemistry management.

Power plant condensate corrosion products

• Conditions: High flow rate hot condensate with iron oxide and copper particles.
• Issue: Particles entering the boiler/resin bed; high cost of one-time fine filtration.
• Identify: iron, copper, particles, temperature, start-up/steady-state load, and backwash performance.
• Solution: Start-up phase 10 µm → Steady-state phase 1–5 µm for backwashing large area pleated filter cartridges; resin pre-coating may be necessary.
• Accuracy / Structure: Start-up phase 10 µm; operation phase 1–5 µm.
• Material: high purity PP or temperature-resistant structure; 70 in high flow rate.
• Acceptance: iron and copper removal, backwash recovery rate, ΔP, and rinse conductivity.
• Limitations: material maximum temperature and reverse ΔP must be verified against actual structure.

Wastewater, high-purity water, and small systems

High-purity water usage points

• Conditions: RO/EDI permeate used at branch, storage tank, or terminal water take-off points.
• Issues: pipeline biofilm and particulate matter causing point exceedance; low flow rates suitable for single-use components.
• Identify: particles, colonies, TOC, resistivity, temperature, and stagnation time.
• Solution: Circulation system hygiene control → 0.45 µm pre-coat → 0.2 µm PES capsule terminal point.
• Accuracy / Structure: 0.45/0.2 µm double-layer or 0.2 µm terminal.
• Material: hydrophilic PES/PSU, PP shell; low extractables, suitable for integrity testing.
• Acceptance: integrity, colonies, particles, TOC, and change time.
• Limitations: capsule can only protect a single point, not the entire loop biofilm.

Small/Emergency Seawater Desalination Systems

• Operating Conditions: Vehicle-mounted, shipboard, or island-based equipment; water intake varies significantly with limited maintenance access.
• Issues: Insufficient pre-treatment capacity; filter cartridge inventory and interfaces not standardized.
• Identify: worst turbidity, flow rate, pump suction, salinity, spare parts, and shutdown flushing.
• Solution: 100–300 µm cleanable screen → 20/10 µm depth filtration → 5 µm pleated filter → SWRO; provide a bypass flushing design.
• Accuracy / Structure：100–300→20→10→5 µm。
• Material：Standardized PP filter cartridges with seawater-resistant housing; unified end cap。
• Acceptance：Flow rate, conductivity, filter ΔP, energy consumption, and spare parts consumption。
• Boundary：Emergency equipment still requires disinfection and microbial management of produced water。

Fault Diagnosis