1000 tons/day soybean protein extraction production wastewater treatment

1. Design basic data

1.1 Design processing scale

Design the scale of comprehensive wastewater treatment: The project needs to treat 281772.6t/a (939t/d) of wastewater, the project design treatment capacity is 1000t/d, the civil engineering is expected to be designed according to the total design water volume, and the equipment is designed according to the total water volume; the land planning is 45*20 meters.

1.2 Sewage station inlet water quality

The sewage station provided by the owner needs to treat the following water quality:

According to the owner, the specific water quality of production wastewater is as follows:

1.3 Sewage station effluent quality

1.3.1 Recycled water quality

The quality of recycled water shall comply with the "Water Quality for Industrial Water Use in Urban Wastewater Recycling" (GB/T19923-2005)

The recycled water effluent from the project's production wastewater after treatment meets the requirements of Table 1 of "Water Quality for Industrial Water Use in Urban Wastewater Recycling" (GB/T19923-2024) for cold open circulating cooling water make-up water. The recyclable water volume is 210,000 m3/a. The water demand of the project's cooling circulation system is 542,700 m3/a. Therefore, the recycled water generated after the treatment of the project's production wastewater can be fully reused without being discharged.

Table 1 Recycled water is used as cooling water in the water quality standards for industrial water sources. The specific indicators are as follows:

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1.3.2 Drainage quality

The concentrated water produced by the sewage treatment plant meets the sewage plant takeover standards and is taken over to the Jiangcheng sewage treatment plant.

The water quality of external drainage shall comply with the Class B standard in Table 1 of the Comprehensive Sewage Discharge Standard (GB8978-1996) and the Water Quality Standard for Sewage Discharge into Urban Sewers (GB/T31962-2015). The specific water discharge indicators are:

1.4 Wastewater discharge from the whole plant

2. Wastewater treatment process design

According to the characteristics of raw water, the requirements of the owner, the scale of land, and in line with the principles of economic applicability, energy conservation and emission reduction, a plan of resource treatment using advanced biochemical + membrane separation technology is proposed. After treatment, all the deep-treated product water is reused as production cooling circulating water supplement water and domestic miscellaneous water. The treatment process of this plan is designed as "air flotation + AO integration + MBR + ultrafiltration + reverse osmosis water production for cooling circulating water, and reverse osmosis concentrated water for external discharge" process.

2.1 Design processing efficiency of each process section

2.2 Wastewater treatment process flow chart

2.3 Description of core processes for wastewater treatment

2.3.1 Flotation tank

The function of flotation is to separate low-density substances such as grease in wastewater by density screening, so as to float out the lighter grease and grease, thereby achieving the separation of water and oil substances.

2.3.2AO integrated simultaneous nitrification and denitrification process

The core of the AO integrated (integrated nitroso simultaneous denitrification) process is to control the simultaneous progress of nitrification and denitrification reactions in one tank, so that the microbial flora of the two reactions can coexist in the system, thereby achieving efficient removal of ammonia nitrogen, total nitrogen and COD. At the same time, it can reduce the power consumption required for aeration, and by extending the residence time, reduce the amount of residual sludge, and save sludge treatment costs.

2.3.3MBR membrane system

The effluent from the AO integrated pool directly enters the MBR membrane pool. Through the efficient interception of the membrane, all bacteria and suspension are intercepted in the membrane pool. At the same time, it can effectively intercept nitrifying bacteria, so that the nitrification reaction proceeds smoothly and NH4-N is effectively removed. At the same time, it can intercept macromolecular organic matter that is difficult to degrade, prolong its residence time in the reactor, and maximize its degradation. The sludge at the end of the membrane pool is returned to the front section through the sludge return pump, and the excess residual sludge is discharged from the system, thereby controlling the concentration and activity of the activated sludge in the system.

2.3.4 Introduction to Ultrafiltration Technology

Ultrafiltration is a pressurized membrane separation technology, that is, under a certain pressure, small molecular solutes and solvents are allowed to pass through a special membrane with a certain pore size, while large molecular solutes cannot pass through and remain on one side of the membrane, thereby partially purifying the large molecular substances. When water passes through the ultrafiltration membrane, most of the colloids and particles contained in the water can be removed, and a large amount of suspended organic matter can also be removed.

2.3.5 Reverse Osmosis Technology

Reverse osmosis is also called reverse osmosis (RO). It uses a certain pressure to separate the solvent in the solution through a reverse osmosis membrane (or semi-permeable membrane). Because it is opposite to the direction of natural osmosis, it is called reverse osmosis. According to the different osmotic pressures of various materials, the reverse osmosis method with a pressure greater than the osmotic pressure can achieve the purpose of separation, extraction, purification and concentration.