COD Removal from High Salt Wastewater in the Food Industry

1. Preface

As the saying goes, food is the most important thing for the people. China has a large population and a high demand for various staple snacks.

At the same time, the food industry also generates a large amount of wastewater, especially in the case of pickled food wastewater, which has prominent characteristics. It has a high organic content but a single component, making it easy to be treated by biochemical systems. However, its high salt content also results in this type of wastewater not being able to directly enter the biochemical system, which is contradictory to each other.

Directly steaming salt, which contains a large amount of organic matter, can cause poor salt whiteness and generate hazardous waste with high processing costs, which is not conducive to economic benefits.

So a new solution is needed, seeking treatment solutions from two aspects: salt evaporation or biochemistry.

2. Other common solutions

At present, there are several treatment methods for such high salt and high COD wastewater

1) Steam salt method

Steaming salt and then entering the biochemical system for treatment is the most direct and simple mature process. This type of process has been applied for a long time and has relatively mature processes and experience.

This type of method allows the effluent to directly enter the biochemical system, with lower backend costs, and this type of wastewater has high biodegradability and simple treatment after salt evaporation.

However, the biggest problem with the salt evaporation method is the cost and hazardous waste generated at the salt evaporation end. The evaporation cost has been improved with the application of new equipment such as MVR, but the hazardous waste generated cannot be processed routinely and can only be entrusted to qualified units for processing, which incurs high costs.

The use of salt steaming method requires comprehensive consideration of both the front-end and back-end.

2) PSB photosynthetic halophilic bacteria

This method also belongs to the biochemical treatment method, and an additional biochemical treatment tank is added regularly to which PSB photosynthetic halophilic bacteria are added. These microorganisms can solidify the salt in the wastewater, transfer the salt from the wastewater to the sludge, and the effluent has a lower salt content and reduces COD.

This type of method saves the cost of evaporation and salt evaporation. Although sludge is hazardous waste, the amount generated is similar to that of ordinary biochemical systems, and the cost of hazardous waste does not increase compared to biochemical systems with the same processing capacity.

The current problem is that PSB bacteria have certain limitations in salt tolerance and require long-term and regular addition of microbial agents. The activity and reproduction of microorganisms directly affect the effluent situation, and the treatment capacity of such microorganisms varies for different water qualities.

3. Haipu customized solutions

Haipu Functional Materials Co., Ltd. has developed a special adsorption material for efficient treatment of COD. This material can effectively adsorb COD in wastewater under high salt conditions, reducing effluent COD. The salt produced by salt evaporation will be relatively pure with high whiteness, which can be treated as ordinary solid waste, recycled and reused, or processed into other by-products.

The high concentration desorbed solution can directly enter the biochemical system without increasing costs, and due to the special nature of the food industry, this type of salt can mostly be recovered.

The COD and salt content in the wastewater of a large pickled fruit enterprise are both high, and the salt component is only ordinary edible sodium chloride. This wastewater cannot directly enter the existing biochemical system, and steaming salt directly will produce a large amount of dark hazardous waste.

After being treated with our company's special adsorbent, the salt evaporation whiteness of the effluent has significantly increased and has reached the reuse standard. The treatment effect is shown in the figure:

The upper part shows the direct evaporation of raw water, and the lower part shows the treated wastewater and salt evaporation situation. The salt whiteness has reached 65, which can be directly used as feed salt or reused.