Do You Know How to Operate a Swimming Pool Water Treatment System?
How can a swimming pool maintain water that is crystal clear while remaining safe and non-toxic? This is where the pool water treatment system comes into play. Impurities in the pool water primarily consist of dirt, bacteria, cosmetics, body oils, and sweat introduced by swimmers, as well as debris, dust, and leaves that accumulate in the pool, along with bacteria and algae. Most of these impurities are insoluble in water. Due to their varying specific gravities, some float on the surface, some remain suspended in the water, and others settle at the bottom. The movement of these impurities-rising or sinking-occurs over time, with the speed influenced by both specific gravity and water flow.
If there is no circulation system for the pool surface, that area becomes a "dead zone" (stagnant water); similarly, without circulating flow and filtration at the bottom, the pool floor becomes a dead zone. When treated water enters the pool, it must be distributed evenly to avoid dead zones and short-circuiting (where water bypasses the main treatment path). A swimming pool water treatment system primarily comprises the water circulation system, filtration system, and disinfection system. How do these systems operate?
I. Swimming Pool Water Circulation System
The circulation system centers on the circulation pump. This pump provides the power necessary for processes such as purification, filtration, heating, and disinfection. It ensures that the required circulation volume and turnover rate are met, overcomes resistance within the equipment, and provides the necessary pressure for water to enter the pool.
Common circulation methods include the counter-flow system, the mixed-flow system, and the standard flow system.
The standard flow system is simple to construct and cost-effective; however, it is prone to dead zones and the accumulation of floating debris on the surface, which requires manual removal. In this system, the entire volume of circulating water is introduced through inlets located on the end or side walls (below the water surface), while the corresponding volume of used water is drawn out through outlets at the bottom for purification before being returned to the pool.
The counter-flow system offers relatively uniform water distribution but has higher construction requirements-including the need for a balance tank-and is susceptible to water short-circuiting. In this circulation method, the entire volume of circulating water is fed into the pool through inlets or channels located at the pool bottom. Used water is then collected via overflow channels situated along the outer edges of the pool walls, purified, and returned to the pool for continued use.
The mixed-flow method imposes stringent construction requirements and is rarely adopted. In this system, 60%–70% of the circulating water is collected via overflow return channels along the pool walls, while the remaining 30%–40% is collected through return outlets at the pool bottom. These two streams are combined, purified, and then returned to the pool through the bottom inlets.
II. Swimming Pool Water Filtration System
Swimming pool sand filters purify water by using a specialized medium-quartz sand-to trap microscopic debris on the sand's surface. Once installed and filled with quartz sand, the system operates by using a pump to drive pool water through the piping and into the filter unit. As the water passes through the sand bed, fine dirt and dust particles are filtered out. The purified water exits the bottom of the filter and returns to the pool via the piping system, completing the circulation cycle.
These filters are constructed from fiberglass-reinforced plastic (FRP), offering resistance to deformation, corrosion, and wear. When water flows through the quartz sand bed, impurities and organic matter are trapped, effectively filtering the water. The more debris the bed captures, the clearer the filtered water becomes, indicating higher filtration efficiency. However, the filter requires periodic backwashing and drainage to remove accumulated debris; failure to do so can compromise subsequent filtration performance.
III. Swimming Pool Water Disinfection System
Common methods for disinfecting swimming pool water include chlorination, ozonation, and copper-silver ion disinfection.
A major advantage of liquid chlorine disinfection is the residual disinfecting effect provided by the chlorine; it is also cost-effective, easy to use, and does not require complex equipment. However, chlorine gas is toxic, so safety precautions are essential during use to prevent leaks. Furthermore, chlorination often generates various harmful substances-specifically disinfection by-products known for their carcinogenic, mutagenic, and teratogenic effects, such as chloroform and chloroacetic acid. Additionally, liquid chlorine is ineffective against *Cryptosporidium* and its oocysts; consequently, traditional chlorination is gradually being replaced by other disinfection methods.
Ozone disinfection systems are categorized into partial-flow and full-flow ozone dosing systems.
Copper-silver ion disinfection has become a mature technology. Practical tests demonstrate optimal results when combining 0.4 mg/L of copper ions and 0.04 mg/L of silver ions with a small amount of another disinfectant. Notably, experiments regarding drinking water have shown excellent results at concentrations well below safety standards; thus, this technology is widely applied in drinking water and circulating cooling water systems. Copper-silver ion disinfection offers several advantages: it produces no toxic by-products and causes no secondary pollution; the agents are colorless, odorless, and chemically stable; performance is unaffected by temperature, ensuring long-lasting bactericidal effects; and the system requires no dedicated personnel for management or maintenance.
IV. Swimming Pool Heating System
With increasing national emphasis on environmental protection, heating methods relying on coal or oil have largely been banned. While natural gas connections often incur exorbitant fees (sometimes hundreds of thousands), air-source heat pumps offer a welcome alternative. Air-source heat pumps designed for swimming pools extract heat from the ambient air (acting as a low-temperature heat source) and transfer it to the pool water. The system primarily consists of the heat pump unit and a circulation pump. The circulation pump draws cooler pool water into the unit's heat exchanger (typically a titanium coil) for heating before returning it to the pool; this process typically raises the water temperature by 3°C per cycle. Over time, the pool water gradually reaches the design temperature, at which point the unit shuts down.
Swimming pool water treatment is a complex process; therefore, when planning to build a pool, it is essential to engage a professional company for the design. Regardless of the specific water treatment method chosen, the ultimate goal is to effectively manage and maintain pool water quality.