What are the Design Criteria for Attached Growth Systems?
Fixed-film procedures (also known as attached-growth processes) are biological wastewater treatment techniques in which the biomass is connected to some form of medium. Rock, ceramic, plastic debris, and slag are common media found in wastewater treatment facilities.
The growth on the medium is mostly made up of aerobic bacteria. These organisms are comparable to those seen in other types of secondary biological therapy. Free-swimming and stalked ciliates, rotifers, nematodes, and a variety of other microorganisms are among the microorganisms present. The biomass loses its capacity to stick to the medium as it thickens and is sloughed. Attached-growth methods are simple to run and stress resistant, but they provide less process control flexibility than activated-sludge systems.
Role of microorganisms in the attached growth systems
The main function of microorganisms in the attached-growth processes is to transform aqueous and particulate organic materials into cell mass, which is assessed as biochemical oxygen demand (BOD). Microorganisms in a traditional attached-growth process require oxygen to break down organic materials (food) for growth and survival. BOD reduces with time as wastewater travels through the medium, resulting in an increase in cell mass.
Environmental factors that influence the health and growth of microorganisms
To sustain a healthy, expanding population of microorganisms, the attached-growth process must work in the right environment. The operator must keep a close eye on the process to ensure that the correct circumstances are in place for effective attached-growth performance.
Designing guidelines for Attached Growth Systems
The complete design standards being provided as a generic guideline for all of the linked growth units becomes a hurdle when each media producer asserts his own values of surface area to unit volume of his media. At the same time, it's important not to lose sight of the technology's benefits.
Other Design criteria’s to be considered are briefly discussed here:
Freeboard: The suggested minimum and maximum freeboard ranges from 0.6 to 0.9 metres. For modest systems, some states allow 0.3 m of freeboard, while others need 0.6 m.
Flow Distribution: A frequent need is for buildings to properly partition hydraulic and organic loads between two major cells. To provide uniform flow distribution, this is usually enlarged to incorporate numerous intake locations. Most states allow just one discharge point for secondary cells, although main cells are typically recommended to have several exits.
Influent Discharge Apron: A frequent condition for influent discharge to a main cell is that the flow enters a shallow, saucer-shaped depression and that the discharge line end sit on a concrete apron big enough to avoid soil erosion.
Piping and Pipe Connections: In most states, the allowed piping materials, such as ductile iron, plastic, or lined pipes, are defined. Anti-seep collars or similar devices should be used when pipes breach the pond seal to avoid leaks around the pipes. Hydraulic capacity is commonly expressed as 250 percent of the system's design maximum day flow rate. Most states require that multi-cell systems' pipework provide for parallel and series operation, as well as options for by-passing each cell. It's also common to need provisions for emptying each cell.
Settling Ponds: Although settling ponds and polishing ponds are frequently used interchangeably, they are not the same thing. A settling pond is often located near the start of the treatment series, although it can also be found towards the conclusion. The time wastewater is kept in a settling pond might range from 24 hours to a percentage of the time it takes water to pass through the whole system. A hydraulic residence time (HRT) of more than 10 to 15 days might arise as a result of this. At the average design flow rate, a two-day HRT will give greater control.
Miscellaneous: To limit access and discourage trespassing, all of the requirements require that some form of fence be installed. To keep animals from approaching the site, some jurisdictions just demand a fence with a few strands of 2-8 barbed wire. Others are more cautious, requiring the installation of a chain-link fence with barbed wire strands at the top to prevent entry. Gates should be wide enough to allow maintenance trucks to enter the building, and they should be locked.
Feel free to contact Netsol Water with any queries you may have about custom-designing and manufacturing of biological wastewater treatment systems. Contact us on +91 9650608473