There are various systems available for the treatment of sewage, ranging from 1 KLD to 1 MLD. When a sewage treatment system is designed to cater to a single building or a group of buildings, it is referred to as a small or decentralized sewage treatment plant.

Small-scale sewage treatment plants are also popular as packaged, and plug-and-play sewage treatment plants. These types of treatment plants have become possible due to advancements in technology, automation, and control systems. They can now be operated and monitored with ease, which was previously a highly technical job of an environmental engineer operating city-level large treatment plants. While bio-septic tanks and anaerobic treatment systems also fall into this category, they are no longer considered viable treatment options due to their inability to meet stringent treatment norms.

When these systems are prefabricated, they become plug-and-play units but require built-at-site collection tanks and other post-treatment tanks and machine rooms. Such plug-and-play systems are not manufactured to project needs and have a high chance of failing. Therefore, it is always advisable to construct the civil requirements according to project needs and install machinery and technology that is tailor-made for the project to achieve the objective of treatment and have a hassle-free operation.

Hiring a technically qualified STP operator can be a challenging task, so it would be logical to choose a sewage treatment technology that can operate automatically and monitor the operation with a controller that is programmed to log operational data. IoT is now available in many plants where expert intervention and attention can be given to a plant remotely.

Therefore, a small sewage treatment plant should not be seen as just a fabricated unit, but as a treatment system that is designed according to project needs, intelligently operated, remotely controlled, and has the flexibility to incorporate future stringent statutory requirements.