BOD treatment in wastewater

 

Introduction

During daily activities, people always create large amounts of wastewater from bathing, cooking, cleaning… from apartments, offices, schools, hospitals, markets. , restaurant Hotel. This amount of wastewater contains many organic substances, inorganic residues and harmful microorganisms. If not treated, it will pollute the environment and cause disease in humans

Composition and properties of residential wastewater

The main components ofresidential wastewater are residues from kitchens, toilets, leaching substances, organic matter, bacteria, pathogenic microorganisms, and unpleasant odors. bear….
The concentration of substances in residential wastewater is estimated as follows:

Residential wastewater treatment technology

Residential wastewater treatment process

Step 1. Preliminary treatment

Wastewater from the kitchen and food area will be sent to the grease separator system. Then, along with the wastewater from the septic tank, it is transferred to the equalization tank.

Water is sent through a trash screen system to remove large trash. In the equalization tank, there are two submersible pumps. The submersible pump is responsible for pumping wastewater from the equalization tank to the biological system.

In addition, the air conditioning tank is equipped with an aeration system. To create wastewater disturbance to avoid sedimentation. At the same time, anaerobic decomposition occurs in this tank and creates a homogeneous environment. Feed the waste stream before going through the next treatment steps.

Step 2. ASBR batch biological treatment.

The biological treatment tank system includes a Selector buffer tank and two ASBR batch aerobic biological tanks

First, water is put into the Selector buffer tank to stabilize the environment. At the same time, add nutrients such as Phosphorus and Carbon sources (sugar/molasses…).

Wastewater after passing through the buffer tank is evenly distributed to the ASBR biological treatment system. In the tank, a gas distribution pipe system is installed to provide oxygen for the biological treatment process.

The tank functions as both a biological reactor and a sedimentation tank.

Wastewater is put into each compartment depending on the cycle.
In an ASBR tank, a cycle includes 3 separate processes: Filling – reactive aeration (50% of the entire process), settling without aeration (25% of the process) and draining (25% of the process), over a period of 6 hours/cycle.

These three processes take place sequentially in the same SBR tank, according to the principle of repeating each batch. At the same time, each tank will perform different processes in a treatment cycle, ensuring wastewater is continuously treated. The stages are as follows:

•  Filling and reaction (3 hours): The amount of time aeration or agitation is applied to achieve the desired biological treatment effect.
• Settlement (1.5 hours): Aeration or agitation is temporarily stopped to allow solids to settle to the bottom of the tank, leaving a clear layer of treated water above.
• Water collection (1.5 hours): The water will be drained out and go into the disinfection tank.

Excess activated sludge generated during the treatment process is automatically discharged and pumped to the sludge treatment tank.

Step 3: Disinfect

After mechanical and biological treatment, the wastewater will be sent to a disinfection tank to remove harmful microorganisms before being discharged into the environment.

Output standards of residential wastewater treatment