Ordinary activated sand filter: a reliable "guardian" in the field of water treatment
Today, as water shortage and pollution problems become increasingly prominent, efficient and stable water treatment equipment has become the key to ensuring water quality and safety. As a classic water treatment device, ordinary activated sand filters are widely used in municipal sewage, industrial wastewater, tap water pretreatment and other scenarios due to their advantages of continuous operation, easy maintenance, and high cost performance, becoming the "backbone" in the field of water treatment.
1. Definition and core structure
Compared with the enhanced type (such as the special type for phosphorus and denitrification), the ordinary activated sand filter is a continuous water treatment equipment that uses quartz sand as the filter material and integrates filtration and backwash functions. Its core structure includes:
- Filter body: cylindrical or rectangular tank, providing filtering space;
- Sand bed: It is composed of quartz sand with a particle size of 0.8-1.2mm, and the thickness is usually 1.2-1.5m. It is the core area for trapping impurities;
- Water distribution system: The top water is evenly distributed, and the bottom air distribution ensures the backwash effect;
- Backwash system: consisting of an air compressor and a backwash pump, which removes pollutants in the sand layer through combined air and water flushing;
- Cleaner: Located at the top of the filter, it cleans the rising dirty sand. The impurities are discharged with the wastewater, and the clean sand falls back to the sand bed.
2. Working principle: synergy of continuous filtration and backwashing
The characteristic of the ordinary activated sand filter is that filtration and backwashing are performed simultaneously without shutting down. Its workflow can be divided into two steps:
1. Filtration process: Raw water enters the filter tank from the top and passes through the sand bed from top to bottom. Suspended solids (SS), colloids, algae, etc. in the water are intercepted by the sand layer, and the purified water is discharged from the bottom outlet.
2. Backwash process: At the same time, compressed air and backwash water enter from the bottom, forming a fluidized area at the bottom of the sand bed (sand particles are suspended). The dirty sand rises to the top cleaner under the action of air flow and water flow. Through air stirring and water flushing, the impurities are stripped off and discharged with the waste water. The cleaned sand falls back to the sand bed due to gravity, completing the cycle.
This continuous operation mode avoids the downtime gap during backwashing of traditional filters and greatly improves processing efficiency.
3. Core advantages: Stable and reliable "King of Cost-Effectiveness"
The reason why ordinary activated sand filters are widely used is due to their significant advantages:
- Continuous operation, high efficiency: no need to shut down for backwashing, stable processing capacity, suitable for large-scale water treatment scenarios;
- Good filtration effect: the removal rate of SS can reach more than 90%, and it can also remove part of COD, BOD and phosphorus, and the effluent turbidity can be reduced to less than 5NTU;
- Easy maintenance: simple structure, no complicated wearing parts, routine maintenance only requires checking the sand layer height, backwash pressure and water quality indicators;
- Small footprint: integrated design, no need for additional backwash water tanks or sedimentation tanks, saving space;
- Low operating costs: The sand material has a lifespan of 5-10 years, and the energy consumption is only 1/3 of traditional filters, reducing long-term operating costs.
4. Application scenarios: covering water treatment needs in many fields
Ordinary activated sand filters have a wide range of applications. Typical scenarios include:
- Advanced treatment of municipal sewage: As a depth filtration unit after secondary treatment, it removes residual SS and makes the effluent meet Class A discharge standards or reuse requirements;
- Industrial wastewater pretreatment: such as food processing, textile, chemical and other industries, to remove suspended solids in wastewater and protect subsequent biological treatment or membrane treatment equipment;
- Tap water pretreatment: remove sediment, algae, and colloids in raw water to reduce the pressure of subsequent disinfection and purification;
- Circulating water system: circulating filtration of swimming pool water and landscape water to keep the water clear;
- Rural drinking water project: Treat suspended solids in well water or surface water to improve drinking water safety.
5. Key points of daily maintenance
In order to ensure the long-term stable operation of the equipment, the following maintenance matters need to be paid attention to:
1. Sand layer management: Check the height of the sand layer regularly. If the amount of sand is reduced due to wear or loss, quartz sand needs to be replenished in time;
2. Backwash system inspection: Check the air compressor pressure (usually 0.4-0.6MPa) and backwash water pressure (0.2-0.3MPa) every week, and clear the nozzles from clogging;
3. Water quality monitoring: Monitor the inlet and outlet water SS and turbidity every day. If the outlet water quality drops, the backwash intensity or frequency needs to be adjusted;
4. Equipment sealing: Check the sealing condition of flanges and valves every month to prevent water leakage;
5. Electrical maintenance: Check the sensors and motors of the control system every quarter to ensure normal operation.
Conclusion
Ordinary activated sand filters occupy an irreplaceable position in the field of water treatment due to their classic design, stable performance and high cost performance. Whether it is municipal engineering or industrial applications, it can effectively solve the problem of suspended solids removal and protect water quality safety. With the improvement of environmental protection requirements, ordinary activated sand filters will continue to play their role as "reliable guards", and will also be upgraded in the direction of intelligence and energy saving to better adapt to future water treatment needs.
(The full text is about 1050 words)
