In order to enhance employees' understanding of reverse osmosis (RO) equipment, Amanda Water Treatment Engineer Ares conducted training sessions for the company's staff on industrial and residential RO systems. The training covered four main areas: the standard components of RO systems, an overview of industrial and residential RO equipment, how to identify RO system models, and common issues with RO systems along with solutions.
I.Standard Components of Reverse Osmosis (RO) Systems
1.Principle of Reverse Osmosis
Osmosis is a fundamental natural process where water or another solvent from a low-concentration solution passes through a semi-permeable membrane into a higher-concentration solution.
Reverse osmosis, on the other hand, involves applying pressure to the high-concentration side of the membrane. When this pressure surpasses the osmotic pressure, the solvent moves in the opposite direction of natural osmosis. As a result, the low-pressure side of the membrane yields the permeate, or purified water, while the high-pressure side contains the concentrated solution
2.Filtration Precision of Reverse Osmosis
Reverse osmosis filtration precision is categorized into microfiltration, ultrafiltration, nanofiltration, and reverse osmosis, with each level providing progressively higher filtration precision.
3.Pretreatment Unit
3.1 Multimedia Filter The multimedia filter removes most visible suspended solids, reducing water turbidity. The top layer of anthracite prevents filter media collapse caused by uneven water distribution within the filter.
Other filter media can be added according to specific filtration needs, such as:
· AKM: A filter media made from glass that can replace quartz sand. It offers the advantages of slight adsorptive properties and a surface resistant to bacterial growth, which helps prevent secondary contamination.
· KDF: A high-purity copper-zinc alloy with varying product compositions that may result in slightly different effects. It primarily removes heavy metals and inhibits microbial growth.
· Manganese Sand: Composed mainly of manganese dioxide, it is used to remove iron and manganese from water. Manganese sand is typically chosen when the iron content in water is high.
· Fluoride Removal Media: This term does not refer to a specific product but includes commonly used media such as activated alumina and tricalcium phosphate granules, which remove fluoride ions from water.
3.2 Activated Carbon Filter
Common types include granular activated carbon (GAC) filters, known as UDF, and high-density compressed activated carbon filters, known as CTO. The main difference between these two lies in the form of the activated carbon: UDF uses granular carbon, while CTO consists of sintered carbon. Due to its sintered structure, CTO has a denser composition, providing superior filtration and adsorption performance, but it is more prone to clogging. In contrast, UDF, with its granular form, is less likely to become blocked by large particles in the water.
Activated carbon filtration is effective at adsorbing residual chlorine in water. While residual chlorine is uncommon in industrial water treatment, it is significant in residential water treatment. Municipal water suppliers use disinfectants like sodium hypochlorite (NaClO) or chlorine dioxide (ClO₂) to prevent bacterial and viral growth during long-distance water transport. This process leaves trace amounts of positively charged chlorine ions in the water, which are harmful to human health. Activated carbon can adsorb these chlorine ions completely. (Reverse osmosis filtration should only proceed when the residual chlorine level is below 0.1 ppm.)
3.2.1-2 Resin Softener and Antiscalant Dosing System
These two types of equipment are used to prevent the formation of scale. In industrial applications, antiscalant dosing systems are commonly preferred due to their lower cost. However, resin softeners offer superior treatment results. Resin softeners remove calcium and magnesium ions directly from the water, effectively softening it. In contrast, antiscalant dosing systems work by adding antiscalants to the water, which inhibit the tendency of calcium and magnesium ions to form scale but do not remove these ions from the water.
3.3 Precision Filter
The precision filter primarily uses polypropylene (PP) fibers for filtration, with a filtration accuracy range of 1-100 microns; most products are typically rated at 5 microns. The quality of PP can be assessed by its weight and rigidity. Generally, heavier and less deformable PP indicates better quality and higher filtration accuracy.
4.Core Units of Reverse Osmosis
High-Pressure Pump: Its main function is to provide sufficient pressure to push water molecules through the semi-permeable membrane. The quality of the pump is crucial for the continuous and stable operation of the water treatment system.
RO Membrane Housing: Also known as an RO membrane pressure vessel, its primary role is to provide a sealed pressure container for the RO membrane and protect it from external physical damage, ensuring the system operates normally. RO membrane housings can be classified by:
1.Material: stainless steel or fiberglass-reinforced plastic (FRP).
2.Connection Type: quick-connect, threaded, or clamped connections.
3.Structure: end port or side port.
4.Diameter: 4-inch or 8-inch.
5.Length: one-membrane to seven-membrane housings.
RO Membrane Size: The size and surface area of the RO membrane are directly proportional to the water production rate. A larger membrane surface area results in a higher water production capacity.
Classification of Reverse Osmosis Membranes:
· By Pressure: ultra-low pressure, low pressure, brackish water, and seawater desalination.
· By Resistance: standard and anti-fouling.
· By Application: residential and industrial use.
5. Common Terms in Reverse Osmosis
System Recovery Rate: The percentage of raw water that is converted into purified water after treatment. For example, a 75% recovery rate means that for every 100 liters of raw water, 75 liters are converted into purified water.
System Salt Rejection Rate: The percentage of dissolved impurities removed from the water by the system. A higher salt rejection rate indicates the system is more effective at removing salts from the water.
Single-Stage (Double-Stage) Reverse Osmosis System: A single-stage system means that the raw water undergoes one pass through the reverse osmosis process, while a double-stage system subjects the water to two passes, further improving water quality.
Multi-Stage, Multi-Unit Configuration: "Stages" refer to the number of reverse osmosis membrane elements the raw water passes through, while "units" indicate that the produced brine is passed through reverse osmosis again. Multi-stage systems improve recovery rates, while multi-unit systems enhance the desalination rate.
Wastewater Ratio: The ratio of the volume of purified water produced to the volume of wastewater generated.
Conductivity (TDS): This indicates the total amount of dissolved substances in water. The higher the conductivity, the more impurities are present in the water. Conversely, lower conductivity indicates fewer impurities.
II. Introduction to Industrial and Residential Reverse Osmosis Equipment
1. Industrial Reverse Osmosis Equipment
Common industrial reverse osmosis processes:
2.Comparison Between Residential and Industrial Reverse Osmosis Equipment
Residential reverse osmosis systems can be seen as a scaled-down version of industrial reverse osmosis systems. The basic principles are the same: raw water first passes through a pre-filtration system to meet the standards required for entry into the reverse osmosis membrane. The water is then pressurized by a high-pressure pump and passes through the membrane to produce purified water.
The key difference lies in the fact that industrial systems often handle more complex water conditions, so their pre-filtration systems tend to vary accordingly.
Additionally, the functions of high-pressure and low-pressure switches in industrial RO systems differ from those in residential systems. In industrial systems, the low-pressure switch cuts off power when water pressure is too low to prevent the high-pressure pump from running dry and causing damage. The high-pressure switch cuts off power when water pressure becomes too high, preventing excessive internal pressure that could damage the reverse osmosis membrane and housing.
In residential RO systems, the low-pressure switch activates the system when water pressure is sufficient and shuts it down when the pressure is too low. The high-pressure switch stops the system from producing water when the storage tank is full and the pressure reaches a set threshold.
III. How to Determine the Model of Reverse Osmosis Equipment
Core points for determining the equipment model:
1. Distinguish whether it is a single-stage, double-stage, or even triple-stage system.
2. Observe the number of reverse osmosis membrane housings.
3. Identify the model of the reverse osmosis membrane housing.
4. Determine the specifications and quantity of the reverse osmosis membranes used in the entire system.
5. Ask the customer for the flow rate and head parameters of the high-pressure pump.
IV. Common Issues with Reverse Osmosis Equipment and Troubleshooting Approaches
Common Issues:
1. Leaks (e.g., loose pipe connections, flanges, quick-connect fittings, etc.)
2. No Water Production or Low Water Production (e.g., inadequate pretreatment leading to membrane clogging)
3. System Fails to Start (e.g., insufficient water pressure, power supply issues, pump failure, controller malfunction, etc.)
4. Poor Water Quality (e.g., system design issues, fluctuations in feed water quality)
5. System Instability (e.g., unstable supply pressure, low water temperature)
Troubleshooting Approach:
Overall First, Then Local:
Start with the overall system—check equipment status, feed water conditions, product water quality, pretreatment system, and high-pressure pump. Then focus on local issues—inspect membrane elements, pipes, valves, and the control system.
Pressure is the Core Indicator:
Ensure that the feed water pressure meets the requirements. Check whether the pressure drop across individual membranes is too high, and verify that the pressure switch settings are correct.
Flow Rate is the Key Indicator:
When designing the reverse osmosis system, determine the flow rate based on the customer's water production needs, water quality requirements, and the feed water quality.
Analyze the Overall System First, Then Focus on Specific Areas:
Pay attention to details that are easily overlooked, such as a customer forgetting to open the wastewater valve, which could cause system failure.
After the theoretical training, the Amanda team visited the reverse osmosis equipment factory, where Amanda Water Treatment Engineer Ares provided an on-site explanation of the construction of reverse osmosis equipment.
Through this training, the Amanda sales team gained a clearer understanding of reverse osmosis equipment, especially its principles. They now have new ideas and better solutions for addressing customer inquiries. Overall, attention to detail is key to success. With continuous learning and improvement, the Amanda team will become even stronger.
