Secondary Treatment


Secondary treatment involves biological treatment for degrading the BOD and COD present in the incoming effluent. Aqua Designs offers a variety of Effluent specific biological treatment processes.

Submerged Media Reactor (BIOX)

This process involves the utilization of a specifically developed media in UV stabilized poly propylene. The media is immersed in the Aeration basin and enhances the biological degradation process. The media surface provides an ideal condition for the growth of micro organisms which in turn rapidly degrade the incoming BOD. The sludge built on the surface is detached by the rising mass of fine air bubbles through the media.

Air required for the process is provided by means of twin lobe type air blowers which maintain the required flow of air through fine bubble diffusers made up of either EPDM / silicon rubber. The diffusers are located at the bottom of the Aeration tank and are placed in such a manner to ensure a uniform plug flow of dense fine bubbles of air from the bottom to top. The generated biomass is settled in the downstream clarifiers. Sludge recirculation is provided as an optional requirement in this method of treatment.

Media based aeration is ideal for packaged sewage treatment plant and specific effluent treatment applications.

Fluidized Bed Bio Reactor (FBBR)

The FBBR utilizes the same concept of media based aeration. Here, we utilize custom design media in the shape of small cylindrical wheels. The bulk density in the media is maintained in such a manner that it remains floating at all times and easily moves around within the aeration tank. The smaller size of media and the movement further enhances the biodegradation efficiency and provides better sludge dispersion. Media based reactors provide the following additional advantages.

	Reduced retention time
	Higher BOD loading
	More tolerable to inlet BOD fluctuation

The media is prepared of rigid and high quality UV stabilized polypropylene which gives the media high strength and long life. Air dispersion is carried out by providing twin lobe type air blowers which maintain the required flow air through fine bubble diffusers made up of either EPDM / silicon rubber. The diffusers are located at the bottom of the Aeration tank and are placed in such a manner to ensure a uniform plug flow of dense fine bubbles of air from the bottom to top. The generated biomass is settled in the downstream clarifiers. Sludge recirculation is provided as an optional requirement in this method of treatment.

Activated Sludge Process

The conventional Activated Sludge extended system works well for a wide range of effluents and high volume flow rates. The extended aeration process is economical for larger flow rates, compared to media based reactors. Aqua Designs offers several options for the Extended Aeration system.

1. High speed floating aerators

These aerators are preferred where there are limitations to the tank height, temporary installations, augmentation of existing aerator system, restriction to civil works.

2. Fixed Aerators

Slow speed aerators are utilized for Extended Aeration lagoons for

	Higher volume flow rates
	Non constraint of Space
	Civil works option is economical

Fixed Aerators are offered with a custom designed impeller mated to a gear reduction system with a drive. The impeller provides optimum agitation with respect to oxygen transfer, improved design results in lower power consumption to oxygen transfer. Fixed aeration systems are designed with proper access for routine maintenance with all safety aspects.

Diffused Aeration system

Diffused aeration system is used to provide highly efficient biological treatment. Twin lobe type air blowers provide the oxygen required for the oxidation of organic pollutants. The air is distributed through fine bubble membrane type diffusers. The MLSS concentration in the aeration tank is maintained at 3000 - 4000 mg/l by re-circulating the biomass. Diffused aeration systems provide several advantages over the other conventional type aeration.

Since oxygen transfer is done by means of diffusers placed at the bottom, the aeration tank can be designed into any shape to suit site requirement. Diffused aeration systems can operate up to a maximum of 4 mtrs liquid depth which in turn translates to smaller tank size and smaller foot print for the Effluent treatment plant.

Diffused aeration systems are also highly flexible to site location (i.e.) the system can be located in a building basement or below ground level where there is space constraint.

Bio mass recirculation

All secondary stage aeration process involves recirculation of biomass back to the aeration system to maintain the MLSS levels in the aeration tank. The biomass recirculation system provided by Aqua Designs utilizes recirculation pumps which are designed to transfer biomass without major deterioration of flocks. Clarifiers are adopted to handle biological sludge and are designed with specific retention times and rise velocities. This in turn practically eliminates sludge bulking and ensures uniform consistent sludge is re-circulated.

Anaerobic System

Aqua Designs offers anaerobic treatment systems which are generally used upstream of an aeration system. This combination of anaerobic and aerobic system helps to treat high BOD and COD containing effluents. The advantage of utilizing an anaerobic digester as a first stage of treatment is to tackle the higher BOD /COD levels and reduce the load on the downstream treatment steps.

Anaerobic digestor produce a by-product gas which is a mixture of methane and carbon monoxide. This gas has appreciable calorific value and can be utilized as fuel.