About conventional activated sludge process / sludge drying

■ About conventional activated sludge process

A waste water treatment process called conventional activated sludge process is also called conventional process and it is a fundamental process for all activated sludge processes. This process is used the most since 1930 when activated sludge process is developed in Japan, however, it has problems that required condition to operate properly is strict, outputs are largely affected by load fluctuation, removal ratio of nitrogen and phosphorus is low, and so on. Therefore, other activated sludge processes are developed to remedy these problems and improved from the conventional activated sludge process.

Load : amount of pollutants in waste water to be treated. Amount of pollution load can be calculated as the following.
Pollution load (Kg/day) = amount of waste water (M3/day) * pollutants concentration (mg/litter) / 1,000
Pollutants : BOD, SS etc.
BOD, SS: An index of dirtiness. BOD is used for rivers and COD is used for lakes.

The following is flow chart of conventional activated sludge process. 
conventional activated sludge process kenki dryer 14/3/2020

■ Sedimentation tank

The first process of the waste water treatment. Waste water is carried to the sedimentation tank first, then grits and large garbage are removed by being settled out in the tank.

■ The first clarifier
This is a tank to settle small darts which cannot be removed in the sedimentation tank out to the bottom. By letting water flow, darts are precipitated. Darts removed here is called primary sludge and carried to sludge thickener tank together with excess sludge which is described later.

■ Reaction tank
By providing and mixing oxygen into waste water, activated sludge in the waste water is proliferated. This activated sludge decomposes organic matters in waste water and clean the water.

■ The secondary clarifier
Activated sludge which proliferates during decomposition of darts becomes lump-shape and heavier than water. By settling them out, clean water can take out from the top clear layer. The sludge which is settled out here is called excess sludge, and it is treated and disposed after being carried to thickener tank. Also, some of the precipitated activated sludge is returned to reaction tank.

■ Disinfecting facility
Water taken out from the secondary clarifier is sterilized and disinfected here and discharged into river or sea. This facility does the final process of waste water treatment.

■ Sand filtration
Fine suspended solids (SS) which couldn’t be treated in the secondary clarifier are passed through filter materials such as sand, so that nitrogen, phosphorus and BOD are removed.

■ Sludge thickener tank
Primary sludge from the first clarifier and excess sludge from the secondary clarifier are carried to this sludge thickener tank. Density of solid matter is heightened here. By doing this, latter processes such as dehydration become easier.

About activated sludge, please refer to the following page of our web site.

About activate sludge / sludge drying

Types of waste water treatment / sludge drying, slurry drying, waste drying


■ Sludge drying

Water in the sludge thickened in the sludge thickener tank are removed at dehydration process to a certain degree.
However, moisture content is normally more than 80% and the sludge still has adhesiveness and stickiness. Also, latter processes are not easy because of influence of flocculants. Our drying apparatus of KENKI DRYER with international patented technology can surely dry any sticky, adhesive and viscus sludge, and also materials in liquid state like slurry, without clogging inside of the dryer. Also, because of its simple structure, its price is low and apparatus cost of the dryer can be retrieved by reducing industrial waste disposal cost within 3 years. Dried materials can be recycled as fuel, bacterial fertilizer, soil conditioner, etc. since component of the material is hardly changed because of its low-temperature drying method.
It can be applied to a system with pyrolysis apparatus as well.

Sludge drying



Please consider KENKI DRYER for drying of sticky materials, adhesive materials and materials in liquid state that no other dryer can deal with.
Initial, running and maintenance costs are low because of its simple structure based on internationally patented technology.
For sludge drying, costs of our dryers are estimated to be retrieved within 2, 3 years by reducing industrial waste disposal cost.
For raw material slurry drying, laborious works of manual operation will be decreased significantly by replacing box shaped compartment tray dryer with our dryer
In case of organic wastes drying, the waste can be recycled as fuel, fertilizer, soil conditioner and feedstuff after being dried.



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Pyrolyzer Biogreen
A pyrolyser with internationally patented technology which use no fire