Satyakam Mohanty
delves on innovative
water resource
development and
management for
optimizing the
available natural
water flows as well
as reuse of
wastewater.
About three-fourth or seventy five per cent of the earth's surface is covered with world
oceans. However, the fresh water constitutes a very small proportion with 2.7per cent of
the total water available on the earth. Moreover, about 75.2 per cent of the available
fresh water lies frozen in Polar Regions and another 22.6 per cent as ground water.The rest is
available in lakes, rivers, atmosphere, moisture, soil and vegetation.
What is effectively available for consumption and other uses is a small proportion of the
quantity available in rivers, lakes and groundwater.Therefore, there is urgent call for water
resources development and management as most of the water is not available for use and
secondly it is characterized by its highly uneven spatial distribution.
Accordingly, the importance of water has been recognized and greater emphasis is being laid
on its economic use and better management. We all know water is essential for socioeconomic
development and for maintaining healthy ecosystems.
Properly managed water resources are a critical component of growth, poverty reduction and
equity.The livelihoods of the poorest are critically associated with access to water services.
With higher rates of urbanization, increasing demand for drinking water will put stress on
existing water sources.
As energy demand is on the rise, hydropower will need to be a key contributor to clean
energy production.Floods and droughts will continue to threaten farmer livelihoods and
lowland economies.
Therefore, the need arises for Water Resources Management that aims at optimizing the available natural water flows, including surfacewater and
groundwater, to satisfy these competing needs.
Adding uncertainty, climate change will increase the complexity of
managing water resources. In some parts of the world, there will be
more available water but in other parts, including the developing
world, there will be less. Rivers across the world are gradually
becoming environmentally safe to water stressed to water scare.
Integrated Water Resources Management is need of the day for
maintaining ecological flow / environmental. The task at hand is to
make the wastewater useable.
Wastewater is any water that has been adversely affected in quality by
anthropogenic influence.
It comprises liquid waste discharged by domestic residences,
commercial properties, industry, and/or agriculture and can
encompass a wide range of potential contaminants and
concentrations.
Selection of treatment technology (unit operation and processes)
primarily depends on the untreated wastewater characteristics and
levels of various parameters in treated effluent. Degree of treatment is
decided based the treated water quality standards required for
recycled water use and the influent parameters. The performance
indicators of treatment technologies are based on mainly TSS, BOD
and Total Coliform for domestic wastewater.
Most wastewater is treated in industrial-scale wastewater treatment
plants (WWTPs) which may include physical, chemical and biological
treatment processes. Industrial wastewater is treated common
effluent treatment plan and domestic waste in sewage treatment plant.
However, the use of septic tanks and other On-Site Sewage Facilities
(OSSF) is widespread in rural areas. The conventionally adopted
aerobic treatment system is the activated sludge process, based on
the maintenance and recirculation of a complex biomass composed by
micro-organisms able to absorb the organic matter carried in the
wastewater. The sequential batch reactor is an advance treatment
process which provides excellent process control over a wide range of growth by varying the operating strategy in Aerobic or Anoxic
conditions. (This process has been adopted in the Goa Water Supply
and Sewerage Project, a project being managed by a consortium of
Nihon Suido and Louis Berger).
Anaerobic processes are widely applied in the treatment of industrial
waste waters and biological sludge containing high BOD and COD
concentration. Some wastewater may be highly treated and reused as
reclaimed water.For some waste waters ecological approaches using
reed bed systemssuch as constructed wetlands may be appropriate.
Membrane Bio-Reactor (MBR) is an advanced and modern wastewater
treatment technology and comes as a package plant of various capacities
and can reduce the BOD and TSS below 5 mg/l level. The technology of
membrane activated sludge is the combination of an activated sludge
treatment together with a separation of the sludge interstitial water, the
permeate, or micro-filtrate, by micro or ultra-filtration membrane with pore
size of typically 10 nm to 0.5µm.
Modern systems include tertiary treatment by micro filtration or
synthetic membranes as well as ultra- filtration such as Reverse
Osmosis which is becoming more and more feasible. After
membrane filtration and with necessary disinfection, the treated
wastewater is indistinguishable from waters of natural origin
of drinking quality.Nitrates can be removed from wastewater by
microbial denitrification, for which a small amount of methanol is
typically added to provide the bacteria with a source of carbon.
Ozone Waste Water Treatment is also growing in popularity, and requires
the use of an ozone generator, which decontaminates the wateras Ozone
bubbles percolate through the tank.Disposal of wastewaters from an
industrial plant, is a difficult and costly problem. Most petroleum refineries,
chemical and petrochemical plants have onsite facilities to treat their
wastewaters so that the pollutant concentrations in the treated
wastewater comply with thelocal and/or national regulations regarding
disposal of waste waters into community treatment plants or into rivers,
lakes or oceans.Other Industrial processes that produce a lot of wastewaters
such aspaper and pulp production has created environmental
concern leading todevelopment of processes to recycle water use within
plants beforethey have to be cleaned and disposed of.Treated
wastewater can be reused as drinking water, in industry(cooling towers),
in artificial recharge of aquifers, in agricultureand in the rehabilitation of
natural ecosystems.
Now-a-days, even water treatment plants for municipal water
supply are increasingly designed with sludge treatment process
such as sludge thickening and dewatering / dehydration units to
reduce suspended solids from the effluent discharging to the water
bodies (in the Louis Berger managed JICA financed Guwahati
water supply project).
(The author is Managing Director,
Louis Berger Consulting.)