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Simple process
According to the source water characteristics and water production requirements, the following process is adopted:
System description
This system is divided into four parts: pretreatment, reverse osmosis, and sterilization system.
A． Pretreatment system
Pretreatment devices include raw water pumps, dosing systems, mechanical filters, activated carbon filters, fine filters and other equipment. Mainly solve the following problems:
(1) Prevent scaling on the reverse osmosis membrane surface (including the deposition of CaCO 1, CaSO 1, S 2So 1, CaF 2, SiO 2, iron, aluminum oxide, etc. on the membrane surface);
(2) Prevent clogging by colloidal substances and suspended solid particles;
(3) Prevent organic matter from clogging;
(4) Prevent microbial fouling;
(5) Prevent oxidative damage to the membrane caused by oxidizing substances;
(6) Ensure the inlet water temperature and maintain stable water production of the reverse osmosis device.
This ensures the stable operation and service life of the reverse osmosis device.
1. Original water tank
The raw water tank is used to store water from the external network for the pretreatment system.
2. Raw water pump
This system is equipped with a low-pressure water pump to pressurize raw water and provide power source for the pretreatment system.
3. Flocculant dosing system
There is a certain amount of colloidal substances in raw water, and their particle size range is 10-10 -4mm -6. Due to its own dynamic stability and electrification, it is stable in water and direct filtration has almost no effect. The flocculant added to the raw water is basic aluminum chloride (PAC) or high-efficiency flocculant ST. It forms flocs with colloids, particles and other impurities in the raw water, which is beneficial to being filtered by the filter material in the fine sand filter, improving the filtration effect, reducing the turbidity and pollution index of the effluent, and ensuring the SDI of the RO device inlet water is ≤ 4. The dosage of PAC is generally around 2mg/1, and the specific dosage depends on the site conditions.
4. Mechanical filter
This system is equipped with a mechanical filter filled with refined quartz sand to intercept suspended matter, colloids and other impurities in the incoming water. The backwashing time of the equipment is determined by the turbidity of the incoming water, which depends on the turbidity of the raw water.
During backwashing, compressed air is sent into the water at the same time to scrub the filter material. The compressed air intensity is 18-25 liters/second·m.2。
5. Activated carbon filter
This system is equipped with an activated carbon filter. The filter is filled with coconut shell activated carbon, which is used to remove residual chlorine and organic matter, some pigments and harmful substances in the raw water, and reduce the COD content.
Because the irregular inner pores of activated carbon itself make it a breeding ground for microbial growth, a steam high-temperature sterilization device was added. Control the number of bacterial colonies in the effluent to prevent microorganisms from blocking the reverse osmosis and ensure the quality of the effluent.
The backwashing time of the equipment is determined by the turbidity of the incoming water, which depends on the turbidity of the raw water.
During backwashing, compressed air is sent into the water at the same time to scrub the filter material. The compressed air intensity is 18-25 liters/second·m.2。
6. Fine filter
A fine filter is installed in front of the RO device. The purpose is to prevent the pre-mechanical filter or activated carbon filter from operating abnormally (such as the filter layer has not been formed after backwashing or other human factors) for final inspection to prevent particles in the water from entering the ultrafiltration membrane module and damaging the membrane surface.
The fine filter uses polypropylene honeycomb filter element to improve filtration accuracy. When the pressure difference between the filter element reaches 1.0㎏/㎝ 2, the filter element in the filter needs to be replaced.
7. Antiscalant dosing system
Since the source water contains calcium and magnesium ions, and the desalination rate of reverse osmosis is as high as 97%, the concentrated water side is highly concentrated and will produce precipitations such as calcium carbonate, magnesium carbonate, and magnesium sulfate. Precipitation attached to the surface of the reverse osmosis membrane will block the channels of the membrane elements, causing an increase in pressure difference, a decrease in water flux, and a decrease in desalination rate, affecting the normal operation and service life of reverse osmosis. Therefore, a scale inhibitor device is installed in front of the reverse osmosis device for protection to prevent scaling on the concentrated water side of the reverse osmosis device.
B. reverse osmosis system
This system is equipped with a set of 6m 3/h reverse osmosis desalination device.
The reverse osmosis device is the most important part of the system. Whether the design is mature and reasonable not only directly determines whether the RO system can meet the design requirements, but also affects the service life of the RO membrane. The water treated by the RO device can remove most inorganic salts and almost all organic matter and microorganisms.
The RO device has no phase change during the water quality separation process, high desalination rate, small equipment size, automatic operation, strong adaptability, wide application range, and no pollution. The RO devices assembled by our company are mainly imported famous brand components.
(1) RO membrane: American Dow Company
(2) High-pressure pump: Hangzhou South
(3) Automatic flushing device: supporting assembly
1. High pressure pump
The high-pressure pump is selected from Hangzhou Nanfang Company; the pump is made of high-quality stainless steel and has the characteristics of small size, high efficiency, and low noise.
The high-pressure pump is equipped with a soft-start device and a low-pressure protection device to prevent the high-pressure pump from causing strong water flow impact when starting and stopping, and damaging the high-pressure pump and reverse osmosis membrane elements.
2. Reverse osmosis device
The reverse osmosis device is used to remove most ions, organic matter, microorganisms and other impurities in the incoming water, so that the effluent water quality is highly purified.
(1) System equipment selection
The membrane module uses the BW membrane element provided by the American Dow Company, which represents the highest level in the world today. The surface layer is made of a negatively charged aromatic polyamide composite membrane material, which has good resistance to mechanical tension and chemical erosion. The module has a large membrane area and a relatively large water production flux.
The pressure membrane tube is made of fiberglass shell, with a smooth inner wall that is resistant to bacteria and anti-corrosion.
(2) Process design of reverse osmosis device
This system is equipped with a 3reverse osmosis device with a water production capacity of 6m/h. The reverse osmosis device is equipped with three 2-core pressure membrane tubes and six BW365 membrane elements with high desalination rate and high flux. Under the conditions of water inlet volume of 9m 3/h, operating pressure of 1.5Mpa, and recovery rate of 70%, the water production volume of the reverse osmosis device is 6m 3/h, and the desalination rate reaches more than 97%.
(3) Auxiliary configuration
The reverse osmosis concentrated water side is equipped with a solenoid valve, which performs low-pressure flushing every few hours and during shutdown to flush away pollutants on the surface of the reverse osmosis membrane and replace the concentrated water in the pressure membrane tube.
The reverse osmosis device is equipped with an on-site instrument panel that directly displays the pressure of the device's operating conditions, concentrated and fresh water flow, conductivity and other important parameters.
High and low pressure protection switches are installed at the inlet and outlet of the high-pressure pump to ensure safe and reliable operation of the reverse osmosis device.
3. Reverse osmosis cleaning device
No matter how perfect the pretreatment process is, various pollutants present in the water will always accumulate on the reverse osmosis membrane surface over time during long-term operation. As a result, the performance of the device (water production and desalination rate) decreases, and the pressure difference between the inlet and outlet of the component increases. For this reason, in addition to low-pressure flushing before daily starting and stopping the device, regular chemical cleaning is also required.
The cleaning device configured in this system can chemically clean the reverse osmosis device when the component membrane surface is contaminated by the feed water. At the same time, in order to prevent the accumulation of membrane surface pollution, the device adopts PLC program control and automatically flushes the membrane surface for 2 minutes every few hours, which can effectively prevent membrane surface pollution and extend its chemical cleaning cycle and membrane service life.
D. Sterilization system
1. Ozone equipment
This equipment consists of an ozone generator, cooler, air storage tank, and oil-free air compressor.
The gas source is air source, and the gas production rate is 100 grams per hour.
2. Oxidation tower
The reverse osmosis produced water enters the oxidation mixing tower. The ozone generated by the ozone generator enters the oxidation tower and passes through the ozone-resistant microporous metal titanium rods at the bottom of the mixing tower to evenly distribute the gas. It is fully mixed with the water in the oxidation tower to fully kill bacteria, viruses and other harmful substances.
3. Pure water tank
The reverse osmosis produced water is sent to the pure water tank for external network use.
4. Pure water pump
Transport the reverse osmosis produced water to the water point.
5. Metal titanium rod filter
A 0.45um ozone-resistant metal titanium core is installed at the outlet of the pure water pump as a terminal filter to further remove the remains of bacteria and viruses and impurities that may exist in the pipeline to achieve a thorough sterilization effect and improve the purity, thereby preparing high-quality and delicious oxygen-rich drinking purified water.
6. Overview of control system
System operation control method
The control levels are as follows:
(1) Preprocessing part
Mechanical filters and activated carbon filters are equipped with manual valve groups, and operation and backflushing are performed manually.
The dosing pump is interlocked with the raw water pump.
(2) Reverse osmosis part
PLC control of reverse osmosis device.
A conductivity meter is installed at the inlet and outlet of the reverse osmosis device.
The water outlet of the reverse osmosis high-pressure pump is equipped with high-pressure protection. When the outlet water pressure is higher than 2.0Mpa, the high-pressure pump stops running and the device enters the low-pressure flushing state.
There is a solenoid valve on the reverse osmosis concentrated water side, which automatically enters low-pressure flushing every few hours or when the high-pressure pump starts or stops.
state.
(3) Sterilization part
Pure water pump and pure water tank level interlocking.
7. System design technical requirements
(1) Process equipment
1. Multi-media filter (activated carbon filter)
(1) The connecting pipes of each equipment are made of high-quality stainless steel pipes and equipped with stainless steel butterfly valves.
(2) The pressure gauge is a diaphragm gauge.
(3) Equipment production requirements:
(a) All internal pipelines are connected to the body using flanges, and taking into account the convenience of maintenance and component replacement, the materials of internal components comply with the specified requirements, and the fasteners are made of the same material as the internal pipe fittings.
(b) Internal components are fixed and reinforced to withstand the impact of water flow.
(c) The manhole of the container can ensure the access of maintenance personnel to replace parts. The inner surface of the manhole and manhole cover is flush with the inner surface of the container. The holes are equipped with a complete set of components such as hole covers, washers, bolts, nuts and lifting rods.
(d) The water and air intake inside the equipment and the water and air collection devices distribute water and air evenly.
(e) All internal devices, pipe fittings, components, etc. of the container must be installed and fixed in the container before shipment to prevent missing parts and damage or loss during transportation.
(f) Except for special needs, the exterior of all equipment shall not be made of plastic material, and the material shall be equivalent to the anti-corrosion level of the equipment.
(g) The bottom water outlet device uses stainless steel winding pipe.
(h) The equipment is provided with legs.
2. Precision (security) filter
(1) The structure of the precision (security) filter meets the requirements for rapid replacement of filter elements.
(2) A discharge valve is installed on the water pipe entering the precision (security) filter.
(3) The operating flow rate of the precision (security) filter is not greater than 10m 3/h (based on the surface area of the filter element).
(4) The accuracy of the filter element of the precision (security) filter is 5u and 1u.
(5) The body of precision (security) filter equipment is made of stainless steel.
(6) The top of the precision (security) filter is equipped with an exhaust valve.
3. High pressure pump
(1) A pressure switch is installed at the inlet of the high-pressure pump to alarm and stop the pump when the pressure is low.
(2) The high-pressure pump is equipped with a soft-start device (to control the opening speed of the high-pressure pump) to slowly increase the pressure of the high-pressure pump to prevent the membrane module from being impacted by high-pressure water. A pressure switch is also provided to delay the alarm and stop the pump when the pressure is high.
(3) The high-pressure pump and accessories are made of stainless steel.
(4) The sealing method of the high-pressure pump takes anti-corrosion into consideration.
4. RO device
(1) The design flux of RO membrane elements shall not be greater than the maximum flux value specified in the 'Guidelines' of the membrane element manufacturer.
(2) The types and dosing points of the RO device’s water supply, and the selection of chemical cleaning devices are determined based on the characteristics of the membrane components of the reverse osmosis device selected.
(3) The water supply and concentrated water inlet and outlet pipes of each section of the RO device are equipped with interfaces to facilitate connection with the cleaning fluid inlet and outlet pipes during cleaning.
(4) The RO device concentrated water discharge is equipped with a flow control valve to control the water recovery rate.
(5) The RO device is equipped with a program start and stop device, which can delay automatic flushing after deactivation.
(6) Sampling points are set up in the product water pipe of the RO device. The number and location of the sampling points can effectively diagnose and determine system defects.
(7) The RO membrane module is installed on the combination frame, which is equipped with all pipes and joints, as well as all brackets, fasteners, clamps and other accessories.
(8) RO accessories (pipe joints and valves) and the working pressure of each section of the RO device should be matched.
(9) The water inlet pipe of the RO device adopts side water inlet.
(10) The design of the RO modular frame meets the seismic intensity requirements of the factory site.
5. Washing system
(1) The cleaning system includes cleaning boxes, cleaning pumps, security filters, detachable pipes connected to the RO device, and easy-to-disassemble sealing joints.
(2) The material of the cleaning system can be suitable for all cleaning fluids.
6. System pipelines
(1) The pipeline design of the entire system avoids dead corners to prevent the growth of bacteria, and is equipped with a flushing system.
(2) The water supply pipe out of the filter is made of stainless steel, and the pipes in the low-pressure part and the pipes in the high-pressure part are made of corrosion-resistant stainless steel with corresponding media.
(3) The flange adopts a flat welding raised surface structure according to the corresponding pressure grade standard.
(4) The uniformity of water distribution in the RO membrane module water supply system is considered.
7. Water pump
The anti-corrosion performance of raw water pumps, flushing water pumps, intermediate water pumps and metering pumps meet the requirements of the water quality used.
8. Drug injection system
(1) The volume of various drug solution tanks can meet the dosage of drugs for one day and night.
(2) The dosing metering pump is equipped with a filter at the inlet and a voltage regulator at the outlet.
(2) System instrument settings
1. Flow meter
(1) The water inlet pipe of the multi-media filter is equipped with a flow indicator meter.
(2) RO product water and concentrated water discharge equipment are equipped with flow indicators.
2. Pressure gauge
(1) Install pressure gauges on the inlet and outlet pipelines of security filters, multi-media filters, and activated carbon filters.
(2) Pressure indicating gauges are installed at the water inlet and concentrated water outlet of each section of the RO device.
3. Liquid level gauge
Various water tanks are equipped with liquid level gauges.
4. Chemical instruments
RO installs conductivity meters on jellyfish pipes and water outlets.
RO unit equipped with pH meter
