Furthering Technologies for Water, Wastewater Treatment & Recycle

Water is life. Kirloskar Brothers Ltd expounds on various technologies it has adapted to recycle and reuse water/wastewater – essentially, making this scarce resource go the extra mile.

The importance of water in all aspects of life is not lost on anyone, least of all, on India’s rapidly developing industry. This has, in turn, affected the growth of the water industry. Growing urbanisation and industrialisation, coupled with over-exploitation of water resources is expected to push the growth of the water and wastewater management market in the years to come, but industry participants are worried that the existing poor infrastructure and pricing mechanisms may hamper the path.

Growing population has also contributed to the need to create a strong and sustainable water and wastewater infrastructure for the country. It is thus obvious that supply of clean water and effective treatment of wastewater generated across India are crucial for achieving sustainable development in the country.

The water and waste water management industry encompasses multiple techniques for the treatment of water and to overcome water scarcity and conserve water resources. Some of these technologies are listed below:

Water treatment technologies

Conventional system

Conventional treatment consists of coagulation, flocculation, clarification, and filtration, followed by disinfection at the pre and post stage of treatment. Conventional treatment is often preceded by pre-sedimentation tank. The benefit of using conventional systems is that it reduces the concentration of particulate matter including suspended particles, parasites, bacteria, algae, viruses and fungi; and a range of dissolved and particulate material derived from surfaces water sources. 

Tube settler / Lamella settler system

Tube settlers are used for clarifications purposes. This increases the settling capacity of circular clarifiers and/or rectangular sedimentation basins by reducing the vertical distance. A floc particle must settle before agglomeration to form larger particles. Clarifiers equipped with tube settlers can operate at 2-4 times the normal rate of clarifiers without tube settlers.

Wastewater treatment technologies

Conventional Activated Sludge Process (ASP)

This is a suspended growth process used for municipal wastewater treatment. The activated sludge plant involves wastewater aeration tanks with microbial suspension, solid-liquid separation, clarifier, discharge of clarified effluent, wasting of excess biomass, and return of remaining biomass to the aeration tank.

Extended aeration activated sludge process

Extended aeration is the modification of Activated Sludge Process (ASP) and is a part of the endogenous phase that involves the production of cell matter which produces a minimum of excess sludge to be wasted from the system. The range of F/M to be used includes those which produce the least BODS and suspended solids in the effluent while producing sludge with good settling characteristics.

Moving Media Bio-Reactor (MMBR)

MMBR technology employs thousands of polyethylene biofilm carriers operating in mixed motions, within an aerated wastewater treatment basin. Each individual bio carrier increases productivity by providing protected surface area to support the growth of bacteria within its cells. It is this high-density population of bacteria that achieves high-rate biodegradation within the system, while also offering process reliability and ease of operation. This technology has the advantage of facilitating cost-effective treatment with minimal maintenance.

Sequential Batch Reactor (SBR)

Sequencing Batch Reactor (SBR) is an activated sludge process. It operates in a true batch mode with aeration and sludge settlement both occurring in the same tank. The major difference between SBR and conventional continuous-flow activated sludge system is that the SBR tank carries out the functions of equalisation, aeration and sedimentation in a time sequence rather than in the conventional space sequence of continuous-flow systems. In addition, the SBR system can be designed with the ability to treat a wide range of influent volumes whereas the continuous system is based upon a fixed influent flow rate. Thus, there is a degree of flexibility associated with working at a time rather than in a space sequence.

The operating principles of a batch activated sludge process, or SBR is characterised in five discrete periods: anoxic fill, aerated fill, react, settle and decant.

Membrane Bio-Reactor (MBR)

A membrane bioreactor or MBR is an activated sludge process that utilises a physical barrier, the membrane, to filter contaminants from wastewater. Utilising submerged membranes eliminates the need for secondary clarification and tertiary filtration. By decoupling the activated sludge process from the settling characteristics of suspended solids (MLSS), the footprint of a wastewater treatment process can be halved or even reduced further. In addition, a MBR is ideally suited for Biological Nutrient Removal (BNR) applications as coagulated metal salts are easily filtered and captured phosphorous can be collected as Waste Activated Sludge (WAS).

Up-flow Anaerobic Bio-reactor (UABR)

In the UABR process, the whole waste is passed through the anaerobic reactor in an up flow mode, with a Hydraulic Retention Time (HRT) of only about 8-10 hours. No prior sedimentation is required. The anaerobic unit does not need to be filled with stones or any other media; the up-flowing sewage itself forms millions of small ‘granules‘ or particles of sludge, which are held in suspension and provide a large surface area on which the organic matter can be attached and undergo biodegradation.

A high Solid Retention Time (SRT) of 30-50 or more days occurs within the unit. No mixers or aerators are required. The gas produced can be collected and used if desired. Anaerobic systems function satisfactorily when temperatures inside the reactor are above 18–20°C. Excess sludge is removed from time to time through a separate pipe and sent to a simple sand bed for drying.

Trickling filter/bio-tower

Trickling filter is an attached growth process, i.e. process in which micro-organisms responsible for treatment are attached to an inert packing material. Packing material used in attached growth processes include rock, gravel, slag, sand, redwood and a wide range of plastic and other synthetic materials.

Wastewater recycling technologies

Rapid gravity sand filtration

Rapid sand filters use relatively coarse sand and other granular media to remove particles and impurities that have been trapped in a floc through the use of flocculation chemicals—typically salts of aluminium or iron. Water and flocs flow through the filter medium under gravity or under pumped pressure and the flocculated material is trapped in the sand matrix.

Ultra-Filtration membrane technology

Ultra-Filtration (UF) is the process of separating extremely small particles and dissolved molecules from fluids. The primary basis for separation is molecular size. Particles ranging from 1,000 - 1,000,000 molecular weights are retained by ultra -filtration membranes.

Working examples

Kirloskar Brothers Ltd has been at the forefront of the water industry and has executed several projects based on the above technologies.

The 30 MLD Sewage Treatment Plant (STP) for the Steel Authority of India, Bhilai, which is one of the largest recycling treatment plants in India, is based on extended aeration technology. Through this plant, colony sewage is recycled and used for the processes of the steel plant.

Similarly, sewage recycled from the 8.5 MLD STP for the Vadodara Municipal Corporation is now used for gardening purposes, while a 4 MLD STP used by the Hyderabad Urban Development Authority (HUDA) helped in lake reclamation. For water treatment, the company has constructed several plants. A 125 MLD plant based on conventional technology is supplying water to Coimbatore city, whilst plants at Meenad and Pattuvam, based on Lamella clarifier technology (90 and 73 MLD, respectively) have been constructed for the Kerala Water Authority (KWA). Bhopal, in Madhya Pradesh, also has a 195 MLD water treatment plant.

A 12.5 MLD STP based on moving media bioreactor for the Karad Municipal Council, Maharashtra and a 20.5 MLD STP based on sequential batch reactor at Sanand, for the Ahmedabad Municipal Corporation, are also underway.