Case Studies-Wastewater Treatment at A Paper Mill in The Philippines

Current status and requirements of paper mill wastewater treatment

Papermaking is an organic polluted wastewater with high organic wastewater concentration, high suspended solids content, and difficult biodegradation. The SS and COD concentrations of waste paper wastewater are relatively high, and COD is composed of insoluble COD and soluble COD. Usually, insoluble COD accounts for the majority of the total COD composition. When SS is removed from the wastewater, most of the insoluble COD is removed at the same time. Therefore, the main problem to be solved in treating waste paper wastewater is removing SS and COD.

In addition, the BOD5 value in waste paper wastewater is low; the ratio of BOD5 to COD is generally 0.15-0.25, and the biodegradability is poor. The coagulation treatment method can only remove part of the BOD5, and the removal of most of the BOD5 should be mainly solved by biochemical methods.

The following factory mainly uses waste paper as raw material. Therefore, the wastewater quality is waste paper wastewater. It primarily comes from the wastewater generated during waste paper's pulping, screening, flotation, and papermaking. The main components of wastewater are fine suspended fibers, paper fillers, waste paper impurities, and a small amount of pectin, wax, sugar, and various organic and inorganic compounds added during the papermaking process.

The paper mill wastewater treatment plant purchased Yosun environmental protection equipment and applied it to the wastewater treatment process.

（Photo of the installation site of wastewater treatment equipment at a paper mill in the Philippines）

Paper mill wastewater treatment process and treatment effect

The treatment process adopted is: sump -> hydraulic screen -> coagulant tank -> flocculant tank -> Dissolved Air Flotation (our product) -> anoxic tank -> MBBR tank 1 -> MBBR storage tank 2 -> LAMELLA(our product)  -> filter -> discharge.

The short fibers and impurities in the waste pulp are intercepted by the hydraulic screen and collected for recycling. The wastewater enters the regulating tank to adjust the water quality and adjust the water volume to reduce the adverse effects of fluctuations in water quality and volume on subsequent biochemical treatment. The wastewater in the regulating tank is pumped into the flotation tank, where coagulation and flocculants are added to form floccules through reaction. The tiny bubbles released by the dissolved air water preparation system quickly lift the floccules to complete the solid-liquid separation. Most of the pollutants in the wastewater are removed, and the flotation sludge is discharged into the pulp reuse sludge tank. The water in the clear water area of the air flotation machine enters the MBBR pool, where the macromolecular organic matter in the wastewater is converted into small molecular organic matter, and finally decomposed into CH4 and CO2, and then enters the oxidation tank. Under the aeration state of the rotary fan, the microorganisms in the pool further decompose and digest the pollutants in the water through aerobic action, degrading the organic matter into water and carbon dioxide, so that the water quality is purified. After contact oxidation treatment, the wastewater containing suspended microbial particles enters the sedimentation tank for mud-water separation, and the supernatant is filtered through a multi-media filter tank to meet the discharge standard or be reused.

In the pretreatment process of papermaking wastewater, flotation or sedimentation is usually used. By adding coagulants, most of the SS can be removed, and most of the insoluble COD and some soluble COD and BOD5 can be removed to improve the sewage quality, so that the treatment effect of the entire sewage treatment system can be optimized.