An example of papermaking wastewater treatment by mechanical filtration process

Taking the wastewater treatment project of a papermaking enterprise as an example, the paper introduces the effect of fiber filtration flocculation SBR mechanical filtration process in treating papermaking wastewater. The designed water volume is 3000m3 / d.

According to the actual situation and future development plan of the company, a paper enterprise has formulated a set of corresponding sewage treatment scheme, in order to meet the national environmental protection requirements and adapt to the development of the company. The production process of the enterprise is as follows: commercial pulp and waste paper → hydraulic pulper → screening (wedge wire drum screen) and purification → beating → papermaking → calendering and rewinding → finished products → warehousing. Self made pulp and paper machine are the main causes of wastewater.

Suspended solids, easily and hardly degradable organic matter, pH and chroma are the main pollutants in the process of pulping and papermaking. The wastewater discharge is 3000m3 / h.

Brief introduction of technological process

• After the industrial wastewater comes out of the workshop, it first enters the first structure grid, and most of the suspended solids in the water can be removed by the screening effect of the wedge wire screen grid.
• After the removal of suspended solids, the sewage enters the grit chamber, and after sedimentation, the large inorganic particles in the water are removed.
• The effluent is then pumped into the solid-liquid separator, which is mainly used to remove particles with diameter of more than 0.3mm.
• The wastewater entering the regulating tank is then pumped into the chemical flocculation sedimentation device, which can effectively remove 90% of the suspended solids and colloidal substances in the water. At the same time, the effluent can be refluxed by gravity. Part of the return water is used for continuous production, and the other part is sent to the SBR tank for further treatment.

Equipment Selection

• Design and selection of wedge wire screen grille: underground grille, brick concrete structure, steel material, height of 1.2m, width of 0.6m, plane size of 3.0m × 0.6m.
• The form is designed as two gratings in front and back, and the front and rear gratings are both grid bars. The difference is that the front grid spacing is 10 mm and the rear grid spacing is 5 mm.
• The desilting basin is a rectangular brick concrete structure, and the construction mode is a combined construction; The design flow is QH = 140m3 / h, and the effective residence time is HRT = 10min.
• Hydraulic rotation fiber recovery machine: capacity: 150m3 / h, quantity: 1 set.
• Regulating tank: the structure is designed as underground rectangular steel concrete; Design flow: QH = 140m3 / h, effective residence time: HRT = 6h, V effective = 840m3, quantity: 1 set; Submersible sewage pump: model wq150-15, performance parameters: q = 150m3 / h, H = 15m, quantity: 2 sets (one for use and one for standby, equipped with automatic coupling).
• Chemical flocculation sedimentation device: diameter of main machine: Φ 8000mm, height: 5500mm; Quantity: 1 set, water treatment capacity: q = 140m3 / h; Floor area: 50m2; Dosing pump: model: ihg15-80, q = 1.1m3/h, H = 8.5m, n = 0.36kw, quantity: 1 drug dissolving and storing mixer, reducer: model: xld3-17-0.75, speed: 88r / min, n = 1.5KW, quantity: 2 flowmeters: model: lzb-25, 60-600l / h, quantity: 2; Centralized control cabinet: quantity: 1 main machine field control cabinet: quantity: 1.
• Reuse pool: Structure: rectangular steel concrete structure, underground type; Reuse water: 50% of the treated water is reused, and 50% of the treated water goes into the subsequent biochemical treatment part; QH = 70m3 / h, HRT = 4h, veffective = 280M3; Quantity: 1; Lifting pump: model wq80-10, performance parameters: q = 80m3 / h, H = 10m, quantity: 2 sets (one for use and one for standby, equipped with automatic coupling).
• SBR tank: the design structure is semi underground rectangular steel concrete; Design flow: QH = 70m3 / h, effective residence time: HRT = 36h, V effective = 2520m3; Quantity: 1 block, divided into two compartments; Aeration head: BG = I type, quantity: 1 540; Roots blower: quantity: 1 set; Performance parameters: q = 42m3 / h, P = 49kpa.
• Middle pool: designed as underground rectangular steel concrete; Design flow: QH = 70m3 / h, effective residence time: HRT = 4h, V effective = 284m3; Quantity: 1; 9. Mechanical fiber filter; Model: xgg-80. Treatment capacity: 80 m3 / h, filtration rate: 30 m / h.
• concrete structure; Size: D × h=6.0 × 5 (H) m, sludge pump: model zw50-30, performance parameters: q = 50m3 / h, H = 30m, quantity: 2 sets.
• Sludge drying yard: rectangular brick concrete structure, size L × W × h=28 × eighteen × 1.5m × 2。

After the completion of the project, the effluent quality is good. After monitoring, the effluent quality of the plant meets the discharge limit specified in the discharge standard of water pollutants for pulp and paper industry (GB3544-2008), and the effluent quality index of the plant meets the discharge requirements. The process has the advantages of activated sludge process and biofilm process. It has the advantages of less investment cost, small floor area, easy operation and management, and has the value of engineering application and promotion.