(1) Design Basis

1.1 Raw Water Quality: Local municipal tap water; specific water quality unknown.

1.2 Product Water Application: Purified water

1.3 System Output: Stage 1 output 3m³/h (25°C), Stage 2 output 2m³/h (25°C)

1.4 Product Water Quality: Reverse osmosis desalination rate ≥97-98%

1.5 System Requirements:

(1) Water Supply to Plant: Flow ≥4m³/h, Water Temperature 10-35°C

(2) Power Supply to Plant: 15KW/380V, Three-phase Four-wire

(2) Process Description

    Note: System process diagram attached separately

 

2.1 Raw Water Pretreatment Section:

(1) Prevent fouling by colloidal substances, suspended solids, organic matter, and microorganisms.

(2) Prevent oxidative damage to membranes from oxidizing agents.

(3) Maintain stable permeate production from the reverse osmosis unit.

(4) Ensure stable operation and extended service life of the reverse osmosis unit.

(5) The above is based on the following feedwater requirements for the reverse osmosis system:

Silt Density Index (SDI) ≤5    Residual Chlorine (ppm) <0.1

Turbidity <1.0 NTU Water Temperature Range 15-35°C

Lysing Index (LSI) <10

2.2 Raw Water Tank (Customer-Supplied or Procured) (Select Product)

A 5000L stainless steel or plastic tank stores raw water for pumping to downstream water treatment equipment.

2.3 Raw Water Pump

The raw water pump is selected based on a pre-treatment water production capacity of 4 m³/h. One “LINXIAO” model CMF8-30 pump is chosen, with a single-unit flow rate of 6 m³/h, head of 31m, and power of 1.85Kw. This pump features a vertical stainless steel structure, characterized by compact size, high efficiency, and low noise.

2.4 Chemical Dosage System

Adjusts the pH of the feedwater to the secondary reverse osmosis system to ensure the quality of its permeate.

One imported chemical dosing pump is used, equipped with a 40L PE chemical tank.

2.5 Multi-Media Filter

The system is configured with one stainless steel fine sand filter measuring Ф500×1500mm. The filter bed is filled with

well-graded quartz sand with a bed depth of 900mm. Single-unit flow rate: 5.0m³/h; water production: 4m³/h. Fully automatic valve assemblies are connected via stainless steel piping, with treated water SDI ≤5.

2.6 Activated Carbon Filter

The activated carbon filter adsorbs organic matter, residual chlorine, and harmful substances from raw water while reducing COD levels.

This system incorporates one stainless steel activated carbon filter with dimensions Ф500×1500mm. The filter is packed with coconut shell activated carbon, featuring a bed depth of 900mm, a design flow rate of 6m³/h, and a treated water capacity of 4m³/h. Fully automated valve assemblies are connected via stainless steel piping.

2.7 Water Softener

The water softener adsorbs hardness from raw water. As raw water passes through the exchanger, sodium ions exchange with magnesium, calcium, and other cations in the water. This process softens the water, removing or significantly reducing calcium and magnesium salts (producing soft water). This system incorporates a stainless steel filter with dimensions Ф500×1500mm. The filter is packed with cation resin, featuring a bed height of 900mm. Designed for a flow rate of 6m³/h, it processes 5m³/h of water. The fully automated valve assembly utilizes stainless steel piping connections.

2.8 Precision Filter

A precision filter is installed to prevent fine particles in the water from entering the RO membrane elements after the high-pressure pump. One stainless steel precision filter is configured, housing seven 1-meter-long 5μm melt-blown filter cartridges with a water production capacity of 8m³/h. The filter can be maintained for approximately one month. Replace the filter cartridges when the pressure differential across the filter inlet and outlet reaches 1.5kg/cm². The filter structure complies with quick-change requirements.

2.9 High-Pressure Pump

The high-pressure pump is calculated based on the RO system's water production requirements. At 20°C, the RO unit's feed water flow is 4m³/h with an operating pressure of 1.25MPa. The primary pump uses a vertically assembled “TIANHAO” SMP4-160 model, with a flow rate of 4 m³/h, head of 140 m, and power of 3 kW. The secondary pump uses a vertical assembled “TIANHAO” SMP4-160 model, with a flow rate of 4 m³/h, head of 140 m, and power of 3 kW. This pump features a compact size, high power, and low noise.

 

3.0 Reverse Osmosis Section:

The reverse osmosis unit serves as the core desalination component of this project. Water treated through reverse osmosis effectively removes the vast majority of inorganic salts, organic matter, microorganisms, and bacteria. The rationality of its design directly impacts project investment costs, overall system operational efficiency, service life, and operational reliability and simplicity.

3.0-1 System Equipment Selection

The membrane elements utilize polyamide composite membranes supplied by DOW, representing the current international state-of-the-art. These elements feature a three-layer composite structure: an outer layer of aromatic polyamide approximately 2000 angstroms thick, supported by a layer of

microporous polysulfone layer. They withstand high pressure with excellent resistance to mechanical stress and chemical corrosion, achieving 99% removal rates for NaCl, CaCl₂, and MgCl₂.

The pressure housing utilizes fiberglass-reinforced plastic (FRP) tubular casings manufactured by our company, specifically designed for spiral-wound membrane elements. The inner

walls are smooth to inhibit bacterial growth and feature corrosion resistance.

3.0-2 Reverse Osmosis Membrane Assembly

  The primary reverse osmosis unit incorporates 3 single-core pressure membrane tubes housing 3 BW30-365 membrane elements, with an inlet flow rate of 4 m³/h

Operating pressure: 1.25 MPa; Recovery rate: 70-75%; Membrane water production: ≥2.5 m³/h Secondary reverse osmosis unit: Equipped with 2 single-core pressure membrane tubes and 2 BW30-365 membrane elements. Feed water flow: 3 m³/h; Operating pressure: 1.15 MPa; Recovery rate: 80-85%; Membrane water production: ≥2 m³/h

3.0-3 Randomly Configured Products

The reverse osmosis unit is equipped with instruments that directly display critical parameters such as water flow rate, pressure, inlet/outlet conductivity, and the dedicated programmable logic controller (PLC) for the reverse osmosis equipment.

3.0-3 Automatic Flushing System

The primary RO unit employs automatic flushing control. Upon each startup/shutdown and after every 2-3 hours of operation, automatic valves activate to flush the membrane surface for 90-120 seconds. The secondary RO unit uses manual flushing control. During each operation cycle, manual valves are adjusted to open/close the flush valve at startup/shutdown. This effectively prevents membrane surface contamination, extends chemical cleaning intervals, and prolongs membrane service life.

 

Type	Water producing quantity T/H	Electric power	Reclaim rate%	Ultra pure Water Conductivity ( MΩ•cm)	Film quantity	Raw water electrical conductivity US/CM
FRO-0.5T	0.5	1.5	50	≥15MΩ•cm	3	≤300
FRO-0.75T	0.75	3.5	50	≥15MΩ•cm	5	≤300
FRO-1T	1	4.5	75	≥15MΩ•cm	6	≤300
FRO-2T	2.0	5.0	75	≥15MΩ•cm	6	≤300
FRO-2.5T	2.5	6.0	75	≥15MΩ•cm	6	≤300