Modular Membrane Systems Designed by IICT for Water Purification

1. Water purification by Reverse osmosis, Nanofiltration and Ultrafiltration

The plants designed and commissioned by IICT, Hyderabad are skid mounted and run on electric power and will provide 6005000 L/h of purified water from any type of contaminated surface or ground water source. The membranes can remove all the impurities in a single step including excess total dissolved solids (TDS), salinity, hardness, turbidity, heavy metals and germs. The choice of membrane process is based on the raw water quality as shown in Table 1.

Table 1. Choice of membrane process on basis of nature of raw water

Type of Process Nature of Raw Water Raw Water TDS (ppm) Operating Pressure (Atm) Water Recovery (%) Pore diameter (µm)
Reverse Osmosis (RO) Ground water with high contents of TDS & Fluoride/ Arsenic 600-35,000 7-40 50-70 10-4
Nanofiltration (NF) Ground water & Surface water with moderate TDS 300-600 5-25 70-80 10-3
Ultrafiltration (UF) Surface water (TDS < 500 ppm; River & lake water) 200-500 2-10 90-95 10-3-10-2

Figure 1. Compact modular RO/NF water purification System installed at CSIR-IICT Canteen Premises; Frontal and Side Views (Capacity: 1000 L/h)
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The compact system is built incorporating four TFC polyamide RO membranes arranged vertically inside two FRP cylindrical housings. The systems work on the basis of applied pressure, membrane affinity towards water and filtration at a molecular level which allows smaller water molecules to pass through but retains bigger compounds such as turbidity, harmful slats, excess hardness and disease causing micro-organisms.

A feed tank of 3000 L capacity is provided for raw water storage which supplies the feed water to a prefilter micron cartridge to prevent entry of any suspended solid particles followed by the membrane assembly. Blending and partial reject recycle have been provided to maintain adequate product TDS levels and achieve high water recovery. Post treatment assembly constitutes of Ultraviolet (UV) light and Ozonation connected online for disinfection and storage of product water. Figure 1 is the original photograph of model compact RO/NF system installed at IICT canteen premises of 1000 L/h capacity. The system is highly compact and portable making it suitable for remote villages. Four vertical membrane modules of 7.5 m2 area can be seen in the compact membrane module. The permeate water goes to the product water tank and is used for cooking and drinking purposes. The reject from the process is collected in the reject storage tank and is used for washing purposes.

Figure 2. Conventional RO water purification plant installed at IICT For Staff and Students (Capacity: 1000 L/h)
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Figure 2 exhibits a conventional RO system installed at IICT. This is a system with additional pretreatment steps constituting of sand filtration for removal of colloidal impurities, activated carbon filter for removal of odor, color and natural organic matter along with a microfilter cartridge for separation of fine suspended solids. The membrane assembly is horizontal and parallel to the ground. The post treatment again involves UV light and ozonation. This particular design allows product water capacities of even 10,000 L/h. A detailed cost estimate along with logistic requirements are displayed in Table 2. IICT has installed 9 plants of varying capacities in fluoride affected villages of 3 southern states. These plants cater to a population of 1 lakh and bring down fluoride content in ground water from > 5 ppm to within WHO permissible limit of 0.5 ppm.

Table 2. Capital Investment and Operating Cost for Water Purification Systems

Product Capacity
(L/h)
Type of Design Capital Cost
(Rs. in Lakhs)
Operating Cost
(Rs in paise)
Space and Power
RO NF UF RO NF UF
250 Conventional 1.5 1.5 1.0 8 7 5 4m x 3m x 3m
Single phase
(1ϕ)
600 Conventional 2 2 1.5 7 6 4 4m x 4m x 3m
Single phase
(1ϕ)
1000 Conventional 5.5 5.5 3.5 6 4 3 6m x 5m x 5m
Compact 3.5 3.5 3.0 6 5 4 5m x 5m x 4m
(1ϕ & 3ϕ)
2000 Conventional 6 6 4.5 5 4 3 6m x 6m x 5m
(3ϕ)
Compact 5 5 4 4 4 3 5m x 5m x 4m
5000 Conventional 12.5 12.5 10 4 3 3 8m x 8m x 6m
(3ϕ)
10000 Conventional 20 20 16 3 3 2 12m x 12m x 8m(3ϕ)

Table 3. Implementation of water treatment technologies developed by CSIR-IICT, Hyderabad

Name of Technology Issue/Problem addressed Implementation Status
RO Membrane Technology Fluoride removal 9 plants of 1000 L/h capacity each installed in the following villages: Mylaram, Allahpur, Rachakonda, Nerimetta, Marlapadu & Gaggalapally (Telangana) + Chandrapadu & Karamchedu, (A.P.) + Sethurapatti (Tamil Nadu).
RO Membrane Technology Model Plant for easy sustenance in villages and training of gram panchayat / NGO personnel Successfully implemented in IICT campus. Under operation since 4 years. Provides drinking water to staff, students & canteen. Capacity 1200 L/h
Hollow Fiber Ultrafiltration (UF) Membrane Technology Clarification & disinfection of surface water Requires funding for scale-up of hollow fiber modules to pilot plant level
Hand pump operated submerged UF Device Water purification in flood affected regions through clarification and disinfection Pilot plant of 250 L/h capacity designed and fabricated. Not yet implemented in the field for lack of virus analysis facility and financial constraints
Hand operated mobile water purifier For use during travel or in remote villages Presently fabricated using a commercial UF cartridge. To be implemented after successful incorporation of indigenous hollow fiber membrane
Highly compact RO/Nanofiltration plant with small footprint of
1.5 m x 1 m x 1.5 m
Ground water purification Recently Implemented in IICT Campus for Cooking Purpose. Capacity 1200 L/h
Membrane Bioreactor Kitchen wastewater treatment and recycle Under Installation in IICT campus, Capacity: 500 L/h