The high-temperature hydrothermal treatment method for straw is a technology that uses a high-temperature and high-pressure water environment to treat straw, aiming to improve the biological conversion efficiency and utilization value of straw. This method promotes the hydrolysis of hemicellulose and cellulose in straw by placing it in high-pressure hot water and utilizing the hydrolysis effect under high temperature and pressure environment, thereby improving the enzymatic hydrolysis efficiency and facilitating the subsequent biotransformation process. But it may also generate wastewater. If these wastewater are not treated properly, they will cause pollution to the environment. Therefore, exploring the treatment methods of straw high-temperature wastewater is of great significance for realizing the resource utilization and environmental protection of agricultural waste.

1、 Source and characteristics of straw high-temperature treatment wastewater

High temperature treatment of straw usually involves processes such as high-temperature combustion or gasification, which generate a certain amount of wastewater. These wastewater mainly include cooling water, washing water, and process wastewater. These wastewater often contain high concentrations of organic matter, nutrients such as nitrogen and phosphorus, as well as harmful substances such as heavy metals. They have characteristics such as high chromaticity, high turbidity, and poor biodegradability.

2、 The treatment method of straw high-temperature treatment wastewater

Based on the characteristics of high-temperature treatment of straw wastewater, the following treatment methods can be adopted:

（1）Physical processing method

The physical treatment method mainly includes steps such as grid, precipitation, and filtration, which are used to remove suspended solids, large particle impurities, and oils from wastewater. These steps can effectively reduce the turbidity and chromaticity of wastewater, providing favorable conditions for subsequent treatment.

（2）Chemical treatment method

Chemical treatment is the process of adding chemical agents to cause harmful substances in wastewater to undergo chemical reactions, converting them into substances that are easy to treat or remove. For the treatment of heavy metals, nitrogen, phosphorus and other nutrients in straw high-temperature wastewater, chemical precipitation method, ion exchange method, oxidation-reduction method and other methods can be used for treatment. These methods can effectively remove harmful substances from wastewater, but may cause secondary pollution and require careful selection and treatment.

（3）Biological treatment method

Biological treatment is a method that utilizes the metabolic activity of microorganisms to convert organic matter in wastewater into harmless substances. For high concentration organic matter in straw high-temperature treatment wastewater, biological treatment methods such as anaerobic digestion and aerobic treatment can be used. These methods have the advantages of good processing efficiency and low operating costs, but require longer processing time and stable operating conditions.

（4）Combination processing method

Due to the complexity of high-temperature treatment of wastewater using straw, a single treatment method often fails to achieve ideal treatment results. Therefore, a combination of physical treatment, chemical treatment, and biological treatment can be used to achieve better treatment results. For example, suspended solids and impurities such as oil and fat in wastewater can be removed through physical treatment first, then harmful substances such as heavy metals can be removed through chemical treatment, and finally organic matter can be degraded into harmless substances through biological treatment.

3、 Case analysis of straw high-temperature treatment wastewater treatment

In order to better illustrate the treatment method of straw high-temperature wastewater, our company will introduce a specific case below. A certain treatment plant uses straw high-temperature gasification technology to treat straw, and the wastewater generated undergoes the following specific treatment process:

The waste liquid is collected through the pipeline network, enters the anaerobic digestion tank through the grid, and then enters the regulating tank. The regulating tank is lifted into the transverse cross anaerobic tank by a lift pump. The transverse cross anaerobic tank utilizes the biofilm formed by anaerobic microorganisms attached to the anaerobic packing material, allowing the sewage sludge to fully contact and react. Organic matter undergoes hydrolysis, acidification, and methane formation, removing organic matter from the wastewater and improving its biodegradability.

After anaerobic treatment, the wastewater flows into the biological contact oxidation tank, which can remove most of the COD in the wastewater through aerobic treatment. Subsequently, the wastewater flows into the primary sedimentation tank, which settles the water treated in the previous process. The supernatant enters the ammonia and phosphorus removal tank, and the bottom sediment is used for sludge reflux.

The wastewater flows into the ammonia and phosphorus removal tank by gravity, and the tank is adjusted to a strong alkaline state by adding calcium hydroxide Ca (OH) 2. Under strong alkaline conditions, an aeration device is used to enhance the blowing and desorption of NH4+. At the same time, Ca2+reacts with total phosphorus to produce calcium phosphate precipitation, which can remove the majority of N, P and residual COD and SS. Then, the supernatant flows to the secondary sedimentation tank and is clarified before being discharged in compliance with standards. The sludge in the treatment project is discharged into the sludge tank and regularly cleaned.

4、 Prospects and Suggestions for High Temperature Treatment of Straw Wastewater

With the increasingly strict environmental regulations and people's increasing awareness of environmental protection, the treatment of straw high-temperature wastewater will receive more and more attention. In the future, the treatment of straw high-temperature wastewater will pay more attention to resource utilization and harmlessness. To achieve this goal, it is recommended to take the following measures:

（1）Strengthen technological research and innovation, and develop more efficient and environmentally friendly wastewater treatment methods;

（2）Strengthen the construction and maintenance of wastewater treatment facilities to ensure their stable operation and compliance with discharge standards;

（3）Strengthen the supervision and management of wastewater treatment processes to prevent the occurrence of secondary pollution;

（4）Strengthen environmental protection publicity and education, and raise public awareness and attention to the treatment of straw high-temperature wastewater.

In short, the treatment of straw high-temperature wastewater is an important environmental protection work. By adopting appropriate treatment methods and technological means, the resource utilization and environmental protection of wastewater can be achieved. In the future, we need to continuously strengthen technological research and innovation, improve the efficiency and quality of wastewater treatment, and contribute to achieving sustainable development.