Astim package unit plants with full aerobic activated sludge processes eliminate the odor nuisance and other disturbing problems of sewage.There are two kinds of package system. One of them is Sequential Batch Reactor (SBR), the other one is Continuous System (CSR).

Continuous system 

The wastewater passing trough the coarse screen goes to the aeration section by gravitational flow or a lifting pump. Activated sludge is produced in the aeration section by giving air to the wastewater. The air comes from the blower spreading uniformly by diffusers. After optimized retention time in the aeration phase, a suitable piping transfers the wastewater to the lamella separator, which is designed especialy against shock loads. The wastewater leaves the suspended solids in the lamella separator and is weired to the chlorination section in a clarified form and discharged to the receiving areas such as lake, river or sea. While most of the sludge separated from the wastewater is recirculated to the aeration section with the air lift pump, the excess sludge is taken to the stabilization section and aerated again in order to reduce the sludge amount.

Sequantial Batch Reactor system

Wastewater flow may show flactuations in various parts of the day; for example, during the night hours of the rural zones, industries without midnight shifts or due to seasonal changes of the needs. Considering these conditions SBR package treatment systems are the best solution. This system accomplishes the filling, aeration, settling and emptying operations in the same volume simultaneously following each other. This kind of operation is the basic difference with the previous process system. 

The energy consumption and the required area are close to the continuous process package systems. The tank geometrical shape can be whether horizontal cylindrical or rectangular for transportation purposes in international standard container dimensions. 

The space requirements of ARP plants are smaller than other systems as a result of the high microorganism concentration in the aeration section and the steady feeding of the system with air lifting pump.