Fundamental Concepts: Overview of Water Quality ppt

Dissolved Oxygen¾Organic material ¾If oxygen is available, organic material requires oxygen to decompose ¾Organic material may also decompose in the absence of oxygen ¾More organic mate

Fundamental Concepts: Overview of Water Quality

Ann Kenimer Texas A & M University

University Curriculum Development for

Decentralized Wastewater

Management

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This work was supported by the National Decentralized Water Resources Capacity Development Project (NDWRCDP) with funding provided by the U.S Environmental Protection Agency through a Cooperative Agreement (EPA No CR827881-01-0) with Washington University in St Louis These materials have not been reviewed by the U.S Environmental Protection

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of these materials do not necessarily reflect the views and policies of the NDWRCDP, Washington University, or the U.S Environmental Protection Agency, nor does the mention of trade names or commercial products constitute their endorsement or

recommendation for use.

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These materials are the collective effort of individuals from

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been peer-reviewed and represent the current state of

knowledge/science in this field They were developed through a series of writing and review meetings with the goal of formulating

a consensus on the materials presented These materials do not

necessarily reflect the views and policies of University of

Arkansas, and/or the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT) The mention of trade names or commercial products does not constitute an endorsement or recommendation for use from these individuals or entities, nor does it constitute criticism for similar ones not mentioned.

Kenimer, Ann L., J Villeneuve and S Shelden

2005 Fundamental Concepts: Water Quality Power Point Presentation in (M.A Gross and N.E Deal, eds.) University Curriculum

-Development for Decentralized Wastewater Management National Decentralized Water Resources Capacity Development Project

University of Arkansas, Fayetteville, AR.

Water Pollution

¾Definition: any condition that adversely affects the quality of streams, lakes,

oceans, or groundwater

Water Pollution Impacts

¾Unpolluted water has a wide diversity of aquatic organisms and contains enough dissolved oxygen

¾Polluted water inhibits the growth of

aquatic organisms

Reference Material

¾Standard Methods for the Analysis of

Water and Wastewater American Water Works Association and the American

Public Health Association

¾EPA Methods and Guidance for the

Analysis of Water US Environmental

Protection Agency

Importance of Organic Matter

¾Organic material consumes oxygen in

Dissolved Oxygen

¾There are two important factors that can influence the amount of dissolved oxygen present

¾Water temperature

¾Organic matter

Dissolved Oxygen

¾Organic material

¾If oxygen is available, organic material

requires oxygen to decompose

¾Organic material may also decompose in the absence of oxygen

¾More organic material requires more DO, and will tend to deplete water of DO

Oxygen Demand

¾The oxygen demand is the amount of oxygen required to aerobically oxidize a material

Biochemical Oxygen Demand

¾Biochemical oxygen demand, or BOD is the amount of oxygen used by organisms during the breakdown of organic material

¾BOD is considered an indirect measure of the organic content of a sample

BOD5 Procedure

¾Measure initial DO

¾Incubate sample for 5 days

¾Measure final DO

¾The BOD5 is directly related to the amount

of DO used up over the 5-day period

s V

f

DO i

DO t

BOD

−

=

Ultimate BOD

¾The ultimate BOD measures the total

amount of oxygen needed to oxidize the organic matter and the reduced

nitrogenous compounds

BOD carbonaceous + BOD nitrogenous =

ultimate BOD

Chemical Oxygen Demand (COD)

¾COD is the equivalent amount of oxygen needed to break down organic matter and oxidize nitrogen compounds using strong oxidizing agents

Chemical Oxygen Demand

¾ Another means of measuring oxygen demand needed to oxidize organics and reduced

nitrogenous compounds

¾ Faster than BOD

¾ Always higher than BOD

¾ COD is much higher than BOD in raw wastewaters

¾ COD:BOD ratio is usually less than 2:1 in treated

effluents

¾ COD:BOD ratio is dependent on circumstances and reduces with treatment

Total Organic Carbon

¾Total organic carbon, or TOC, is the amount of organic carbon bound in a sample

Fats, Oil, and Grease

¾Generally listed under one heading called FOG (fats, oils, and grease) as it is often not important to know the exact make-up

of this group of components

Cause many problems:

¾Collect in septic tank requiring pump out over time

¾May clog distribution areas in

poorly-managed systems

¾Fill storage areas, clog ditches and

channels

¾Settle on stream bottoms resulting in

death of valuable benthic biota and loss of habitat and dissolved oxygen in the water column

Total Solid (TS)

¾Total solids of a sample is the matter left behind after drying a sample of water at 105ºC

Total Solids

There are two ways that solid materials may

be classified

¾Suspended solids and dissolved solids

¾Volatile solids and fixed solids

¾Total suspended solids are the part of the sample that may be caught with a 1.5 µm filter

¾Total dissolved solids are the part of the sample that will pass through the filter

¾Total volatile solids is the portion of the

sample lost after the sample has been

heated to 550ºC It is an approximation of the organic material present

¾Total fixed solids is the portion that still

remains after heating It is an

approximation of the mineral matter

present

¾These categories may be combined:

¾Volatile dissolved solids (VDS)

¾Volatile suspended solids (VSS)

¾Fixed dissolved solids (FDS)

¾Fixed suspended solids (FSS)

Solids

¾ The mass of solids per known volume of water is:

Problems associated with excess nutrients:

¾Causes an increase in productivity of

aquatic plants, leading to depleted DO

levels

¾May cause odor problems

¾Extra vegetation near surface may inhibit penetration of light into water

Microbial Organism

¾Serve many important purposes including degrading waste materials

¾Some of them may be dangerous to

human health and must be removed from water

Testing for Microbial Organisms

¾Fecal coliform counts are used as an

indicator organism

¾The sample material is placed in a nutrient bath and set aside in a sterile area

¾The number of colonies that form are

proportional to how many microbial

organisms are present in a sample

Problems associated with excess salt:

¾High salt concentrations detrimental to plant growth and can damage crops

¾Salt can damage equipment, especially some materials which react with the salts

Problems associated with excess metals:

¾Can make water taste and smell bad

¾Can stain

¾Metals in high enough concentrations are pollutants and can be serious health risks

¾Hardness is the concentration of

multivalent cations

¾Hard water can leave scales in pots,

pipes, and hot water heaters More soap

is also needed to clean

¾Soft water has fewer cations making it

harder to remove soap residue