A Packaged Sewage Treatment Plant is used in rural areas, highway rest stops, and trailer parks with a population of 10 to 100 people.

The cyclic-activated sludge system is a combination of secondary treatment and sedimentation. Usually, raw sewage and aerated activated sludge are blended. The settled material is circulated and re-aerated before a certain amount is sent back to the headwork. Unfortunately, this process requires exact monitoring of timing, blending, and aeration which can be difficult to regulate using computer systems connected to sensors. As such, it cannot be used in places with unreliable or badly maintained controls or frequent power outages. However, SBR plants are now being installed in numerous places globally.

Separate basins are used for aeration and settling in extended aeration package plants, which are larger and less sensitive to timing than SBR plants.

Treatment plants generally require a pre-treatment device to get rid of any unsuitable materials that may enter the waste flow (plastics, rags, rocks, and so on). These typically involve one of three mechanisms: trash traps, bar screens, or comminutors. In addition, kitchen drains from food service operations should utilise a grease trap of the appropriate size. Facilities subjected to variable hydraulic loadings may also need flow equalization tanks to maintain a constant rate for the inflow into the plant.

An important part of the secondary treatment plant is the aeration chamber, which accounts for 90% of the treatment process. Generally, domestic wastewater is organic (biodegradable), so aerobic microorganisms can eat the organic material in the presence of oxygen.

In nature, if untreated sewage is discharged into a stream, the bacteria present can decompose it to such a degree that dissolved oxygen levels are reduced to the point where all aquatic life can be killed. Similarly, an extended aeration treatment system works by introducing air (20% oxygen) with blowers and growing bacteria to react with incoming waste from your home or business. The bacteria in the aeration tank break down sewage and create suspended sludge. The liquid produced in this chamber, known as mixed liquor, has a texture like a thin milkshake and can range in colour from coffee with cream to other shades depending on what types of wastes are present.

After the aeration chamber, a settling chamber, or clarifier, is used to allow microorganisms that were grown in the aeration chamber to settle by gravity and create sludge. Most of these microorganisms will later be pumped back to the head of the aeration chamber, where they can again start their cycle of consuming incoming organics found in wastewater. This process is known as return-activated sludge (RAS). The clear liquid present at the top of the clarifier (that was already treated up to 85-90%) is usually sent to a dosing pump station/slow surface sand filter or polishing pond for further treatment (to reach 95%).

MBBR & SAFF technology are also available for reduced footprint designs. The treated discharge is disinfected with chlorine, and the chlorine is removed by a Dichlorination unit. Ultraviolet disinfection is now being used at some facilities to replace chlorination/dichlorination units. Assimilation of the remaining 5% of pollutants into a stream without measurable environmental harm is generally done with sufficient dilution.

Process of Packaged Sewage Treatment Plant

1. Preliminary Treatment

The influent sewage water passes through a bar screen to remove all the large objects like cans, rags, sticks, plastic packets, etc. which are carried in the sewage stream.

2. Secondary Treatment

a. Anaerobic Zone-

In the first stage of PSTP, the solids in raw sewage settle while allowing the scum to float on the surface, and the settled sludge is stabilized by anaerobic digestion.

b. Anoxic Zone-

When the wastewater streams enter the anoxic zone, denitrification occurs by returning the activated sludge from the final sedimentation zone to the anoxic zone; the level of dissolved oxygen in the anoxic zone is approximately 0.2 to 0.5 mg/l. As a result of the breakdown of existing nitrates by anoxic microbes, inert nitrogen gas is released into the atmosphere.

c. Aeration Zone-
In the aeration zone, the sewage from the solid separation zone flows. In the aeration zone, air is diffused by air blowers, which stimulates the growth of bacteria cultures in and around the floating plastic media. A large surface area is provided by the MBBR media, allowing microorganisms to grow more readily.

d. Sedimentation Zone-
As part of the treatment process, organic waste settles in the sedimentation zone. To ensure that the effluent meets the specified sewage parameters, the settled waste at the bottom of the tank is pumped back to the anoxic zone as a return sludge.

3. Tertiary Treatment System:

A pressure sand filter and an activated carbon filter remove suspended solids (TSS), color, and odour from the secondary treated sewage, which is then disinfected with sodium hypochlorite.

Packaged System Product Advantages:

Packaged systems with pre-assembled, skid-mounted, and factory-tested parts require less installation time and reduce construction costs onsite.

– Compact designs for easy integration into existing facilities

– Completed engineering packages with quick delivery

– Comprehensive cleaning capabilities for peak system performance

– Easy operation and maintenance require minimal operator supervision.

APPLICATION AND USES

• Residential and Commercial Complex
• Public Garden and National Park
• Hotel & Resorts
• Restaurants
• Industries
• Institutions
• Hospitals
• Temples
• Government Offices
• Labour Quarters
• Township
• Hostels