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Breakthrough of low temperature and low turbidity water treatment: engineering application of polymer iron sulfate turbidity removal performance
2025-03-13
Low temperature low turbidity water (temperature <10℃, turbidity <30 NTU) has long been regarded as a technical difficulty in the field of water treatment because to its high colloid stability and low flocculation efficiency. With its unique ferric sulfate and engineering adaptability, polyric sulfate (PFS) has achieved breakthrough application in this field in recent years and become one of the core technologies to improve the rate of water quality standards.
1. Difficulties in low temperature and low turbidity water treatment and the advantages of PFS technology
1. Low temperature and low turbidity water treatment challenge
Low temperature restriction: the decrease of water temperature leads to the weakening of molecular kinetic energy, the hydrolysis rate of coagulant decreases by about 2-4 times, the formed flocs are loose and fragile, and the settlement cycle is extended by 30% -50%.
Low turbidity characteristic: the low concentration of suspended matter (<50 mg/L) leads to the stable charge of colloidal particles, and the traditional aluminum salt flocculant is difficult to achieve effective instability through a single electric neutralization.
2. Core technical advantages of PFS
Rapid hydrolysis characteristics: PFS can still be rapidly hydrolyzed at low temperature to produce a multinucleated hydroxyl complex (such as [Fe_3 (OH) _4] ^ {5 +}), which rapidly neutralizes the negative charge of the colloidal surface through a high positive charge density (above + 30 mV).
Strengthening adsorption bridge: its polymer chain structure can cross the energy barrier in low temperature environment, directly adsorb fine particles to form dense alum flower (particle size> 1 mm), and the settlement rate is increased by 40% -60% compared with traditional agents.
Synergy of oxidation: trivalent iron ion (Fe³) can still oxidize some soluble organic matter (such as humic acid) at low temperature, which can be removed by flocculation, and the turbidity removal rate is increased by 15% -20%.
2. Key scenarios and cases of engineering application
1. Municipal drinking water treatment
A northern water plant (raw water temperature 4℃, turbidity 15 NTU) used PFS instead of polyaluminum chloride (PAC), the addition amount decreased from 50 mg/L to 30 mg/L, the settlement time of catkins was shortened from 45 minutes to 25 minutes, and the factory water turbidity was stable at less than 0.5 NTU.
2. Industrial circulating water system
Printing and dyeing wastewater reuse: under 10℃ working conditions, PFS and anionic polyacrylamide (AP AM) reuse, the turbidity removal rate increases from 78% to 95%, and the sludge production is reduced by 20%.
Preparation of ultrapure water in electronics industry: nanoscale silicon particles (particle size <100 nm) were removed by PFS complexation pretreatment, and the subsequent reverse osmosis membrane contamination cycle was extended by more than 3 times.
3. Engineering optimization strategy and technological innovation
1. Dynamic input and addition control technology
Based on the turbidity / temperature online monitoring system, the dynamic adjustment of PFS dosage (10-80 mg/L) is realized to avoid the turbidity rebound and iron ion residue caused by excessive addition.
Case: A sewage treatment plant adopted fuzzy PID control algorithm, the cost of the agent was reduced by 18%, and the ferric concentration of iron ions in the effluent was stable <0.1 mg/L.
2. Compound and efficiency increase process
PFS + PAM combination: after electrical neutralization of PFS, add 0.1-0.5 mg/L APAM enhanced flocs strength, which is suitable for very low turbid water quality with turbidity <10 NTU.
Pre-oxidation enhancement: the combined potassium permanganate (0.2-0.5 mg/L) pre-oxidation, crack the colloid protective layer of organic matter at low temperature, and the PFS dosage is further reduced by 25%.
3. Equipment adaptation and adaptability improvement
Tubular mixer optimization: by increasing the G value (> 500s ¹), the mixing time is shortened to 10 seconds, and the yield of alum peanut is increased by 30%.
Gas flotation-precipitation coupling process: the dissolved air flotation unit is added at the front end of the sedimentation tank, and the microflocs (0.2-0.5 mm) formed by PFS is enriched twice, and the turbidity removal rate is increased by 8% -12%.
4. Technical economy and environmental benefits
Comparison of operation cost: PFS ton water treatment cost is reduced by 0.05-0.12 yuan less than that of PAC, the sludge is reduced by 15% -30%, and the corrosion rate of equipment is reduced by more than 50%.
Sustainability advantage: No aluminum ion residue characteristics make it meet the GB 5749-2022 drinking water standard to avoid the risk of neurotoxicity of traditional aluminum salt.
5. Future development direction
Development of intelligent dosing system: predict water quality fluctuation combined with machine learning model, and realize automatic and accurate regulation of PFS injection.
Research and development of composite agents: to develop a composite preparation of PFS with biological enzymes and nanomaterials to further improve the capture capacity of low-temperature nanocolluids (<10 nm).
Through the innovation of engineering technology, polymer iron sulfate is promoting the leap of low temperature and low turbidity water treatment from "standard difficulty" to "efficient economy", providing key technical support for water supply safety and industrial water saving in high and cold areas.