Introduction
Sugar wastewater mainly comes from the sugar production process and the comprehensive utilization of sugar by-products. It is mainly the wastewater discharged from the sugar production process using beets or sugarcane as raw materials, mixed with chute wastewater, sugar pressing wastewater, distillation wastewater, ground washing water and other comprehensive wastewater.
Characteristics of sugar wastewater
Sugar wastewater is organic wastewater with high COD and BOD, good biodegradability and high chroma. Direct discharge into rivers can easily cause hypoxia and eutrophication of water bodies, affecting the survival of plankton and protozoa in water bodies. In severe cases, algae will reproduce wildly, causing the death of aerobic organisms in the water due to hypoxia, and eventually leading to the deterioration of water bodies.
Sugar wastewater treatment technology At present, the treatment technology of sugar wastewater mainly includes physical and chemical method and biochemical method. Due to the good biodegradability of sugar wastewater, biochemical method is often used for the treatment of this wastewater at home and abroad. The biochemical method mainly includes anaerobic treatment, aerobic treatment, anaerobic-aerobic treatment, etc.
1. Physical and chemical method The physical and chemical method is mainly used for pretreatment of wastewater. The method includes: coagulation sedimentation method, adsorption method, ion exchange method, extraction method, diffusion dialysis method, electrodialysis method, etc.
2. Anaerobic biological method The anaerobic treatment of wastewater is very suitable when the organic matter content is high. Due to the small amount of sludge produced during anaerobic treatment, the requirement for nutrients is low. At the same time, the methane produced can be used as a potential energy source to eliminate the pollution of gas emissions. The investment cost is generally low, and the operation and management costs are much lower than aerobic processes. It has been widely used in the treatment of sugar industry wastewater.
Upflow anaerobic sludge blanket reactor (UASB) is a representative form of anaerobic treatment. In the reactor, wastewater enters evenly from the bottom and moves upward. The lower part of the reactor is a sludge bed with a higher concentration, and the upper part is a suspended sludge bed with a lower concentration. Under normal circumstances, when treating beet sugar wastewater, the volume load can reach 20.7kgCOD/(m3·d), and the COD removal rate is about 82%.
The UASB process also has the following disadvantages: there is no mature design method for the three-phase separator; the cultivation of granular sludge is difficult, and it takes a long time to start up and form stable granular sludge for the first time; most UASB reactors need to properly control the concentration of suspended solids in the inlet water to prevent blockage and short-circuit; the impact load resistance is not strong, and the effluent water quality does not reach the effluent water quality of the traditional secondary treatment process.
3. Aerobic biological method Aerobic biological method mainly includes activated sludge method and biofilm method.
Sequencing batch activated sludge method, the main structure is SBR reaction tank, in which the processes of water inlet, reaction, sedimentation, decanting, sludge discharge, etc. are completed in sequence. Compared with the continuous activated sludge method, this process has the advantages of fewer treatment structures, aerobic stability of sludge, strong resistance to shock load, high oxygen utilization rate, low probability of sludge expansion, and stable treatment effect. This process is usually used in combination with other processes in actual engineering.
Circulating activated sludge system, this process adopts circulating water inlet in operation mode, and the reactor is divided into three zones: selector, anoxic zone and main reaction zone. This process improves the design of activated sludge selector, and has flexible design and operation mode, which not only reflects the advantages of SBR such as simple process and few buildings, but also overcomes some shortcomings of SBR.
Biofilm/activated sludge combined process, this combined process is a sewage biological treatment technology that combines activated sludge method with biofilm method. On the one hand, it has the characteristics of high load of biofilm method, thus reducing the volume of structure and investment; on the other hand, it also has the characteristics of sufficient solid-liquid contact of activated sludge method, high removal efficiency of organic pollutants, and stable and good effluent quality.
4. Anaerobic-aerobic treatment process Anaerobic biological treatment is suitable for the treatment of high-concentration organic wastewater, and has the advantages of low energy consumption, high removal load, and recycling biogas as energy, but its effluent is difficult to meet the discharge standard; while aerobic biological treatment is suitable for treating wastewater with lower concentration, and has the advantages of good effluent quality after purification.
