The source water tank (raw water tank) and sterile water tank are core equipment used for water storage and buffering in water treatment systems, located at the starting and ending points of the treatment process, respectively. Their functions and working principles vary significantly depending on the stage they are in. The following provides a detailed explanation of its function and working principle:
1、 The function and working principle of the source water tank (raw water tank)
1. Core role
The source water tank is the “raw water buffer station” of the water treatment system, mainly used to store the raw water sources to be treated (such as tap water, groundwater, well water, etc.), providing stable and continuous water supply for subsequent treatment units, and avoiding the impact of fluctuations in raw water supply (such as unstable pressure and sudden flow) on system operation.
The specific functions include:
Balancing inlet pressure and flow rate: If the raw water is directly taken from the municipal pipeline network or well, the pressure and flow rate may fluctuate due to factors such as peak water usage periods and pump start stop. The source water tank can be adjusted through buffering to ensure stable water flow into the pre-treatment system (such as flow rate fluctuations of ≤± 5%).
Preliminary sedimentation impurities: Large suspended particles (such as sediment and rust) in the raw water can naturally settle in the source water tank (settling time ≥ 30 minutes), reducing the load on subsequent filters (such as sand filters) and extending the service life of the filter material.
Prevent equipment from idling: Monitor the water level in the tank through a liquid level sensor. When the water level is below the set value, the front-end water pump will be linked to shut down, avoiding damage to subsequent processing units (such as high-pressure pumps and filters) due to water shortage and idling.
Adaptive intermittent water supply: If the raw water supply is intermittent (such as a well with timed pumping), the source water tank can store a certain amount of water to ensure 24-hour continuous operation of the water treatment system.
2. Working principle
The operation of the source water tank is based on the simple logic of “gravity buffer+liquid level linkage”, and the process is as follows:
Inlet stage: Raw water enters the source water tank through a pipeline, and the water level inside the tank gradually rises (the inlet method is usually top overflow or bottom inlet to avoid impact and agitation of sediment).
Precipitation stage: When the water flow is stationary in the tank, large particles of impurities (density>1g/cm ³) sink to the bottom of the tank due to gravity, and the upper clear water enters the next stage.
Water outlet stage: After the water level in the tank reaches the set height, the bottom outlet (10-20cm higher than the tank bottom, avoiding sediment) transports water to the pre-treatment system (such as a sand filter) through a water pump.
Liquid level control: Install liquid level sensors (such as float switches and ultrasonic sensors) inside the tank to monitor the water level in real-time
When the water level reaches or exceeds the high liquid level (such as 80% of the tank capacity), stop the inflow of water;
When the water level is ≤ low level (such as 20% of the tank capacity), start the front-end water pump to replenish water. At the same time, if the water level is too low (such as ≤ 10%), trigger an alarm and shut down subsequent equipment to prevent idling.
3. Structural features
Material: mostly made of 304 stainless steel (corrosion-resistant, suitable for drinking scenarios) or PE material (low-cost, suitable for industrial wastewater), large tank bodies are poured with concrete (requiring anti-corrosion lining).
Structure: cylindrical or square, with a conical bottom design (for easy drainage), equipped with:
Water inlet (with valve to control flow);
Water outlet (located in the middle upper part, avoiding sediment);
Discharge outlet (located at the bottom, regularly discharging sediment);
Overflow port (to prevent overflow due to high water level);
Liquid level sensor interface.
2、 The function and working principle of sterile water tank
1. Core role
A sterile water tank is the “pure water storage terminal” of a water treatment system, used to store purified water that has undergone deep purification (such as reverse osmosis, EDI) and sterilization treatment, ensuring that the water quality is not contaminated during storage and transportation. It is mainly used in scenarios such as medicine, food, electronics, etc. that require extremely high levels of water quality and sterility.
The specific functions include:
Aseptic storage: By designing materials, structures, and auxiliary sterilization devices, it prevents microorganisms (bacteria, molds) and dust from entering the tank and contaminating pure water (microbial concentration ≤ 10CFU/mL).
Stable water supply pressure: The pure water stored in the tank can be output through gravity or a pressure pump to balance the instantaneous flow fluctuations of terminal water use (such as during peak water usage in hospitals, the water in the tank can be quickly replenished to avoid sudden drops in pipeline pressure).
Water quality maintenance: Prevent water quality stratification (such as uneven dissolved oxygen and trace salt analysis) when pure water is left standing through a circulation system (such as a tank agitator or pipeline circulation pump), ensuring uniform effluent water quality at the end.
Satisfy aseptic process requirements: In the scenario of pharmaceutical water (such as injection water), aseptic water tanks need to be equipped with online sterilization devices (such as pasteurization) to regularly disinfect the tanks and pipelines, in compliance with GMP standards.
2. Working principle
The core of a sterile water tank is “sealed and anti contaminated+sterile maintenance”, and the process is as follows:
Inlet stage: Pure water after reverse osmosis and ultraviolet sterilization enters the tank through a sterile pipeline (316L stainless steel, polished inner wall). The inlet is usually designed as a spray type to avoid the generation of bubbles (which may carry microorganisms) due to impact.
Aseptic storage stage:
The tank is completely sealed, and the top is connected to the atmosphere through a sterilization grade breathing filter (a hydrophobic membrane with a pore size of 0.22 μ m), which balances the pressure inside the tank and intercepts microorganisms and dust in the air.
If the storage time is long (such as>24 hours), start the agitator (speed 5-10r/min) or circulation pump in the tank to slowly circulate the water flow and prevent microbial growth (stagnant water can easily lead to bacterial growth).
Water outlet stage: The water is transported to the terminal water point through a sterile water pump (sanitary grade centrifugal pump, with smooth impellers and no dead corners), and the pipeline adopts a full flow design (no air retention) to avoid secondary pollution.
Regular sterilization: Sterilize weekly or monthly according to the usage scenario using the following methods:
Pasteurization: circulate hot water at 80-85 ℃ in a tank for 30 minutes to kill microorganisms (suitable for food and pharmaceutical scenes);
Ozone sterilization: Introduce ozone (concentration 0.5-1mg/L), let it sit for 30 minutes, and then aerate to remove residual ozone (suitable for industrial pure water).
3. Structural features
Material: Must be 316L stainless steel (low leaching, chemical corrosion resistance), with mirror polished inner walls (Ra ≤ 0.8 μ m) to prevent microbial adhesion and growth.
Structure: cylindrical (no dead corners design), equipped with:
Aseptic water inlet (with sanitary grade quick connect fittings);
Aseptic water outlet (fully welded to the pipeline, without any thread dead corners);
Respiratory filter (0.22 μ m, steam sterilized);
Blender (sanitary grade, with sterile mechanical seal for shaft seal);
Liquid level sensor (sterile type, such as capacitive sensor, to avoid contact contamination);
Manhole (with silicone sealing ring for easy internal cleaning).
3、 The core difference between the two
Comparison Dimension Source Water Tank Aseptic Water Tank
Front end of water treatment system (pre-treatment) and end of water treatment system (purified)
Purified pure water (sterile, low pollution) with impurities in the raw water to be treated
Core objective: Stable inflow of water, initial sedimentation, sterile storage, and prevention of secondary pollution
Material requirements: 304 stainless steel/PE (basic anti-corrosion is sufficient) 316L stainless steel (high cleanliness, sterilization resistance)
Auxiliary device liquid level sensor, sewage outlet breathing filter, agitator, sterilization device
summarize
The source water tank is the “front-end buffer station” of the water treatment system, which ensures stable inflow of water through buffering and preliminary sedimentation; A sterile water tank is a ‘terminal storage station’ that ensures pure water is not contaminated during storage through sealed design and sterile control. Although both are water storage devices, they differ significantly in structure, function, and working principle due to their different links and water quality requirements, jointly ensuring the continuous operation and effluent quality of the water treatment system.
Post time: Aug-05-2025