Water Quality Analysis - Most Probable Number (MPN) technique

 Aim

To determine the potability of the given water sample

Principle

The major source of human pathogens which are transmitted mainly through oral fecal route, such as those belonging to Salmonella species, Shigella species, pathogenic Escherichia coli, Vibrio cholerae, Yersinia enterocolitica, Campylobacter species, various viruses such as Hepatitis A, Hepatitis E, Rota virus and parasites such as Entamoeba histolytica and Giardia species are drinking water.  To determine the potability of drinking water it is necessary to screen the water sample for the presence of these microorganisms.  Since it is tedious to monitor for these pathogens on a regular basis, possible fecal contamination in the water body is determined by screening for the presence of indicator microorganisms. Among indicators, the coliform group of bacteria is routinely tested.  These are rod shaped, Gram-negative, non-spore forming, motile bacteria which can ferment lactose with the production of acid and gas when incubated at 35–37°C.  Escherichia coli, Enterobacter aerogenes, etc. are coliforms. Escherichia coli is the most common coliform and its presence is principally associated with fecal contamination.

Most probable number (MPN) analysis is a statistical method based on the random dispersion of microorganisms per volume in a given sample to detect fecal coliforms in a water sample.

MPN test is ideally completed in three steps:

1.      Presumptive test

2.      Confirmed test

3.      Completed test

 

Presumptive & Confirmed Test

Principle

In this test, water samples are inoculated into fermentation tubes filled with a selective growth medium (lactose broth), which contain inverted Durham tubes for detection of fermentation gas. Three sets of three lactose broth tubes are inoculated with different measured amounts of the water sample and incubated at 37°C for overnight and observed for gas formation.  Presence of gas indicates a positive presumptive test and indicates the presence of coliforms in the water sample since coliforms are capable of utilizing lactose as carbon source.

The gas formation in lactose fermentation tubes n the presumptive test, indicates that the water is unsafe to drink.  However, gas formation may also be due to some non-coliform organisms such as Clostridium. Confirmed test serves to confirm the presence of coliform bacteria after either a positive or doubtful presumptive test. Eosin methylene blue agar plates are used which contains methylene blue that inhibit gram positive bacteria.  Gram negative lactose fermenters (coliforms) such as E coli produce dark centered small colonies having a green metallic sheen while Enterobacter aerogenes form large colonies and lack metallic sheen.

Procedure

1.      Double strength and single strength lactose broth were prepared and dispersed into test tubes with Durham’s tube and sterilized.

2.    3 tubes containing 10 ml double strength lactose broth and 3 tubes containing 9 ml single strength lactose broth and 3 tubes containing 9.9 ml single strength lactose broth were set up for each water sample.

3.      Using sterile pipette 10 ml of water sample was transferred to a set of 3 tubes containing 10 ml double strength lactose broth and 1 ml water sample was transferred to a set of 3 tubes containing 9 ml single strength lactose broth and 0.1 ml water sample was transferred to set of 3 tubes containing 9.9 ml single strength lactose broth.

4.   A loopful of water sample was also streaked into Eosin methylene blue (EMB) agar plates.  The tubes and plates were incubated 37°C for 24 hours. 

5.  After incubation, tubes were observed for  gas production and the plates were observed for the presence of typical coliform colonies.

Observation 

The production of gas in lactose broth after 24-hour incubation indicates a positive presumptive test for coliform bacteria. 

MPN of bacteria present in 100 ml water can be obtained from Mc Crady's probability table or MPN table by comparing the number of positive and negative tubes observed from the 9 inoculated lactose fermentation tubes.  The MPN index of the water sample obtained by referring the standard table is tabulated in table 1.  The tubes showing positive result are retained and used for confirmed test.

MPN index for samples A, B, C and D were noted as 4, 9, 460 and 0 respectively. This shows the presence of E.coli or Enterobacter respectively. The presence of E.coli was confirmed by the appearance of dark centered small colonies having a green metallic sheen in EMB plates.

Result

The presence of gas in lactose broth and dark centered small colonies with metallic sheen in EMB plates indicates that the water sample is non-potable.  

Presumptive test (Left hand side)

Sl. No.	Tubes showing gas production			MPN Index (per 100 ml)
	Lactose broth (2x) 10 ml	Lactose broth (1x) 1 ml	Lactose broth (1x) 0.1 ml
1	1	0	0	4
2	2	0	0	9
3	3	3	1	460
4	0	0	0	0

 Confirmed test (Left hand side) 

Sl. No.	Colony morphology in EMB plate	Presence / absence of coliforms	Result
1	Dark centred colour colonies with green metallic sheen	Presence of coliforms	Non potable
2	Dark centred colonies with green metallic sheen	Presence of coliforms	Non potable
3	Dark centred colonies with green metallic sheen	Presence of coliforms	Non potable
4	No dark centred colonies with green metallic sheen	Absence of coliforms	Potable

 

Environmental Impact Assessment -EIA

Environmental Impact Assessment -EIA is a management tool to be carried out before any
project or major activity to ensure that it will not in any way harm the environment on a short
term or long term basis. Environmental impact assessment is an analysis of the changes in
physical, bio-physical, and socio-economic characteristics of the environment from a
proposed project to ensure sustainable development.

Any developmental project requires the analysis of the need of such a project involved and a
consideration and assessment of the effect of a proposed development on the environment.
The purpose of environment impact process is to identify the potential beneficial and adverse
impacts of development projects on the environment with respect to the environmental,
social, cultural, and aesthetic considerations.

In recent years, major developmental activities projects have encountered difficulties because
of the lack of study of their relationship with the surrounding environment. Environment
impact assessment is a precautionary measure for preventing the possible harms of a
development project for maintaining the balance between environment and development.

The Government of India issued an Environment Impact Assessment Notification on January
27, 1994 by which Environmental impact assessment (EIA) became a tool to ensure
sustainable development through the evaluation of impacts arising from a major activity
(policy, plan, program, or project) that are likely to have significant environmental effects. It
is anticipatory, participatory and systematic in nature. Efforts should be made for EIA
being viable and less costly.

EIA has become a requirement in more than 100 countries. EIA process concentrates on
problems, conflicts and natural resource constraints which might affect the viability of a
project. It predicts how the developmental project can harm people, their livelihoods and the
other nearby developmental activities. It is a planning tool in decision-making.
The objective of EIA is to mitigate the environmental problems at an early stage of project
planning and design.

Some projects have been found unsustainable due to resource depletion. Others are
abandoned because of public opposition, unforeseen costs, held liable for damages to natural
resources and even been the cause of disastrous accidents. All of these considerations are
necessary for determination of the viability of a project and to decide if a project should be
granted environmental clearance.

Environmental Impact Assessment is one of the tools to satisfy this need of systematic
identification and evaluation of the impacts on the environment caused by a proposed project.
It is a study of the effect of a proposed mining project, plan or program on the environment.

EIA process in India
The role for EIA was formally recognized with an earth summit held at Rio conference in
1992. In India the developmental projects till as recently as the 1980s were implemented with
very little or no environmental concerns. The environmental issues began when a national
committee on environmental planning and coordination was set up under the 4th five year
plan. Till 1980, the subjects of environment and forests were the concern of the Dept of
Science and Technology and Ministry of Agriculture respectively. Later, the issues were
attended by the Dept of Environment in 1980 and then by Ministry of Environment & Forest
(MOEF) in 1985.

In 1980, clearance of large projects from the environmental angle became an administrative
requirement and planning commission and the central investment board asked for such
clearance before according financial sanction.
A major legislative measure for the purpose of environmental clearance was in 1994 when
specific notification was issued under section 3 and rule 5 of the environment protection Act,
1986 called the ―Environment impact Assessment Notification 1994.
The first step in seeking environmental clearance for a development project is to determine
what statutory legislations apply to the particular project. The MOEF has brought out several
notifications restricting the development of industries in specified ecologically sensitive
areas.
Environmental clearance for development projects can be obtained either at the state level or
at the central level depending on certain criteria concerning the characteristics of the project.
However, (regardless of where the final environmental clearance is obtained from), for most
projects the consent must first be taken from the state pollution control board or pollution
control committees in the case of union territories.
Some Projects which require Environmental Clearance
1. Nuclear Power such as Heavy Water Plants, nuclear fuel complex.
2. River Valley projects
3. Ports, Airports
4. Petroleum Refineries.
5. Chemical Fertilizers
6. Petrochemical complexe,s Bulk drugs and pharmaceuticals.
7. Exploration for oil and gas
8. Synthetic Rubber.
9. Asbestos products.
10. Hydrocyanic acid
11. Primary metallurgical industries
12. Integrated paint complex
13. Viscose Staple fiber
14. Storage batteries
15. All tourism projects between 200m—500 meters
16. Thermal Power Plants.
17. Mining projects
18. Highway Projects
19. Forest areas.
20. Distilleries.

21. Pulp, paper and newsprint.
22. Dyes.
23. Cement.
24. Electroplating
Types of EIA
There is a general principle of assessment that applies to EIA, and to other assessment
processes. Different types of Impact assessment are
1. Social Impact Assessment
2. Risk Assessment
3. Life Cycle Analysis
4. Energy Analysis
5. Health Impact Assessment
6. Regulatory Impact Assessment
7. Species Impact Assessment
8. Technology Assessment
9. Economic Assessment
10. Cumulative Impact Assessment
11. Strategic Environmental Assessment
12. Integrated Impact Assessment
13. Climate Impact Assessment
14. Demographic Impact Assessment
15. Development Impact Assessment
16. Ecological Impact Assessment
17. Economic and Fiscal Impact Assessment
18. Environmental Auditing
19. Environmental Impact Assessment
20. Environmental Management Systems
22. Health Impact Assessment
23. Project Evaluation
24. Public Consultation
25. Public Participation
26. Risk Assessment 

27. Social Impact Assessment
28. Strategic Impact Assessment

EIA Process

The process of EIA includes several steps listed below-

(a) Screening: EIA process starts with project screening. Screening is done to determine
whether or not a proposal should be subject to EIA and if so, at what level of detail. The
output of the screening process is often a document called an Initial Environmental
Examination or Evaluation (IEE).
(b) Scoping: The aim of EIA is not to carry out exhaustive studies on all environmental
impacts for all projects. Scoping is used to identify the key issues of concern at an early stage
in the planning process
(c)Baseline data collection: The term "baseline" refers to the collection of background
information related to biophysical, social and economic settings in the proposed project area.
(d)Impact analysis and prediction: Predicting the magnitude of a development, it likely
impacts and evaluating their significance is core of environmental assessment process
(e)Analysis of alternatives: Analysis of alternative is done to establish the preferred or most
environmentally sound, financially feasible and benign option for achieving project
objectives.
(f)Mitigation and impact management: Mitigation is done to avoid, minimize or offset
predicted adverse impacts for environmental management plan or system.
(g)Environmental Management Plan (EMP): An Environmental Management Plan (EMP)
is a detailed plan and schedule of measures necessary to minimize, mitigate, etc. any potential
environmental impacts identified by the EIA. Once the EIA and the significant impacts have
been identified, it is necessary to prepare an Environmental Management Plan.
(h)Environmental Monitoring: Environmental monitoring is the measurement of
environmental indicators over time within a particular geographic area. Monitoring should
focus on the most significant impacts identified in the EIA.
(i)Environmental Impact Statement (EIS): The final EIA report is referred to as an
Environmental Impact Statement (EIS). Most national environmental laws have specified
what the content of EIS should have.
(j)Decision making: At each stage of EIA, decisions are made. These decisions influence
the final decisions made about the EIA. The EIS is submitted to designated authority for
scrutiny before the final decision.
(k)Effective EIA follow-up: In practice, an EMP, which is submitted with the EIS report,
should be used during implementation and operation of the project.
(l)Public hearing and involvement: After the completion of EIA report the law requires that
the public must be informed and consulted on the proposed development after the completion
of EIA report.

VALUED ECOSYSTEM COMPONENTS

The description of the existing conditions of the local environment provides a baseline data.
This permits the identification of the main socio‐ environmental factors that might be
associated with the Project activities.

Valued Ecosystem Components (VECs) are ecosystem components that are considered
to be important or valuable and which require detailed consideration in the EIA process.
The concept of VECs has been used in EIAs to highlight important receptors (individuals
or groups) which could be affected (positively or negatively) by the different aspects
of a project/activity. VECs are fundamental to the EIA process.

The impacts of the Project activities on each of the “Valued ecosystem Components” are
evaluated using a significant ranking process.

Environmental Resource	Valued Ecosystems Component	Importance of the Valued Ecosystem Component
Air and Climate	Air Quality	·     Effects on air for local resident ·     Health implications for all user ·     Effects on the ecosystem
	Climate	·     Contribution to global warming
Land	Geomorphology and  Landscape	·     Changes in land morphology  ·     Use of non‐renewable resources ·     Importance to local community  ·     Effects of waste disposal methods
Water	Groundwater Quality	·    Sustainability issues (is groundwater considered a highly limited renewable resource in the area?) ·    Effects on  local  use  (irrigation  and drinking).
	Surface Water Quality	·  Sustainability issues ·  Effects on local use (irrigation, drinking and transportation)   ·  Health implications for all users
	River Water  Quality	·  Effects on local use (fisheries, transportation) ·    Health implications for all  users
Ecology and Biodiversity	Terrestrial Ecology  and Biodiversity	·  Importance to biodiversity value  (International, National and Regional)  ·  Important for ecosystem well  being and proper functioning ·  Use to community
	Marine Ecology and  Biodiversity	·    Importance to the well being of all biological content of  the ecosystem ·    High biological value  (International, national and Regional)  ·    Economic use to community
Human Environment	Socio‐Economic  Activities	·  Employment opportunities  ·  Community welfare
	Community Health and Safety	·  Operations impact on  community safety  ·  Reduction of gas flaring
	Noise Pollution	·  Nuisance to local  community ·  Influence on biological  diversity
	Agriculture	·  Socio‐economic  importance   ·  National and community value creation
	Light Pollution	·  Nuisance  to  local  community  and  ecosystem

Thus, EIA (Environmental impact assessment) ensures consideration of environmental
implications before making a final decision of assessing the environmental attribute.

 One of the main strengths of environmental assessment (EA) is its flexibility.
 Project planning processes can integrate EIA as essential step giving sensitivity to
the social and economic as well as environmental impacts of projects.
 The EIA can help establish and strengthen decision-making and communication
mechanisms within a project. It can also pave the way for introducing innovations.
 An EIA may reveal sound environmental, social or economic reasons for shifting a
project's direction.
 By considering, opinions and aspirations of local people, the EIA process may also
function as a project control mechanism.

EIA focuses on problems, conflicts or natural resource constraints that could affect the
viability of a project. It also examines implications of a project that might harm people,
their homeland or their livelihoods, or other nearby developments. After predicting the
problems, a EIA identifies measures to minimise the problems and outlines ways to
improve the project’s suitability for its proposed environment.

EIA has been recognised as the most valuable, inter-disciplinary and objective decision-
making tool with respect to alternate routes for development, process technologies and
project sites. It is considered an ideal anticipatory mechanism allowing measures that
ensure environmental compatibility with socio-economic development.