Department of Environmental Sciences

Jahangirnagar University

Savar, Dhaka-1342

Descriptions on Some Parameters

of Hydrochemistry

Submitted By

Abu Khairul Bashar

Class Roll: 584

Session 2011-12

Submitted To

Dr. Syed Hafizur Rahman

Professor

Department of

Environmental Sciences

Hydrochemistry is the process of measuring the

condition of water according to the requirements of

more than one biotic species or any human purpose. It

is most commonly used to refer to a set of standards

which compliance is tested against. Hydrochemistry is

the subdivision of hydrogeology that deals with the

chemical characteristics of water. In Hydrochemistry,

there are needed so many parameters. Such as-

DO

BOD

COD

TDS

TSS

TOC

Iron(Fe)

Heavy Metal

Trace Element

Microorganism

Chlorination

Hardness

Dissolved Oxygen refers to the volume of oxygen that

is contained in water. Oxygen enters the water by

photosynthesis of aquatic biota and by the transfer of

oxygen across the air-water interface. The amount of

DO in water is dependent on the water temperature. DO

is a very important indicator of a water body’s ability to

support aquatic life. Oxygen is more easily dissolved

into water at low altitudes than high altitudes because of

higher atmospheric pressure. DO concentrations are

higher in the winter than in the summer. The colder the

water, the more oxygen can be dissolved water.

Biochemical oxygen demand is a measure of the

oxygen used by microorganisms to decompose the

organic matter. When BOD levels are high, DO levels

decrease because the oxygen that is available in the

water is being consumed by the bacteria. Since less DO

is available in the water, fish and other aquatic

organisms may not survive. The BOD test takes 5days

to complete and is performed using a DO test kit.

The amount of oxygen needed to consume the organic

and inorganic materials is called chemical oxygen

demand (COD). COD has the advantage over BOD in

that the analysis can be completed within a few hours

whereas BOD requires 5 days. The major drawback of

the COD test is the presence of hazardous chemicals

toxic waste disposal. The UV absorption can be

considered as an alternative method for COD. The COD

is a rapid and precise method for determination of

aggregate organic matter. COD value can be related to

TOC value also which is a measure of organic carbon

atoms in a sample.

BOD level(in ppm) Water Quality

1-2 Very good

3-5 Fair: Moderately clean

6-9 Poor: somewhat polluted

100 or greater Very poor: very polluted

The expression of ‘’total dissolved solid’’ (TDS) refers

to the total amount of all inorganic and organic

substances including minerals, salts, cat ions, anions,

metals that are dispersed within a volume of water. TDS

concentrations are the cat ions and anions in water.

Sources for TDS include agricultural run-off, urban run-

off, industrial wastewater, sewage and natural sources

such as leaves, silt, plankton and rocks. Piping and

plumbing also release metals in water.

Total Suspended Solids (TSS) are solids in water that

can be trapped by a filter. TSS can include a wide

variety of material, such as silt, decaying plant and

animal matter, industrial wastes, and sewage. High

concentrations of suspended solids can cause many

problems for stream health and aquatic life. High TSS

can block light from reaching submerged vegetation. As

the amount of light passing through the water is

reduced, photosynthesis slows down. Reduced rates of

photosynthesis causes less dissolved oxygen to be

released into the water by plants. If light is completely

blocked from bottom dwelling plants, the plants will

stop producing oxygen and will die. As the plants are

decomposed, bacteria will use up even more oxygen

from the water. Low dissolved oxygen can lead to fish

kills. High TSS can also cause an increase in surface

water temperature, because the suspended particles

absorb heat from sunlight. This can cause dissolved

oxygen levels to fall even further (because warmer

waters can hold less DO), and can harm aquatic life in

many other ways, as discussed in the temperature

section.

Total organic carbon (TOC) is the amount of carbon

bound in an organic compound and is often used as a

non-specific indicator of water quality or cleanliness of

pharmaceutical manufacturing equipment. A typical

analysis for TOC measures both the total carbon present

and the so-called "inorganic carbon" (IC), the latter

representing the content of dissolved carbon dioxide

and carbonic acid salts. Subtracting the inorganic

carbon from the total carbon yields TOC. Another

common variant of TOC analysis involves removing the

IC portion first and then measuring the leftover carbon.

TOC detection is an important measurement because of

the effects it may have on the environment, human

health, and manufacturing processes. TOC is a highly

sensitive, non-specific measurement of all organics

present in a sample. It, therefore, can be used to

regulate the organic chemical discharge to the

environment in a manufacturing plant. In addition, low

TOC can confirm the absence of potentially harmful

organic chemicals in water used to manufacture

pharmaceutical products. TOC is also of interest in the

field of potable water purification due to disinfection of

byproducts. Inorganic carbon poses little to no threat.

Typically, iron exists in water in two different forms,

soluble ferrous or insoluble ferric. Soluble ferrous iron

is dissolved in the water and thus clears, while insoluble

ferric iron will be very visible. Excessive amounts of

iron in water (more than ten parts per million) will give

food and drink a very unpleasant, metallic flavor.

Additionally, water with too much iron could stain

clothing and appliances if spilled. Iron is not a hazard to

health, so there are no health-related risks involved

when water contains too much iron. After doing a water

test to determine that there is a problem with iron, there

are many treatment options available, such as aeration,

filtration, softening and zonation.

A heavy metal is any one of a number of elements that

exhibit metallic properties, which includes transition

metals lanthanides actinides as well as the metalloids

Arsenic and Antimony. Typically the term refers to

elements of atomic number 21 or higher (e.g. Scandium

or above) the term heavy metal chiefly arose with

discussions of pollutants discharged to the environment

in the form of air, water or soil contaminants. While

many heavy metals have considerable toxicity, others

are considered not deemed to possess significant toxic

properties, and, in fact, several of these elements

including zinc, iron, copper, chromium and cobalt are

necessary for metabolic function for a large class of

organisms.

A trace element is a chemical element whose

concentration is less than 1000 ppm or 0.1% of a rock's

composition. The term is used mainly in igneous

petrology. Trace elements will either prefer liquid or

solid phase. If compatible with a mineral, it will prefer a

solid phase (e.g., Ni compatible with Olivine). If it is

incompatible with an element it will prefer a liquid

phase. The measurement of this ratio is known as the

partition coefficient. Trace elements can be substituted

for network-forming captions in mineral structures.

Minerals do not have to contain trace elements, i.e.,

they do not have to appear in the mineral's chemical

formula. When practicing biodynamic farming it is

important to utilize the trace elements of the soil, in

order to give strength to the roots. Hydroponic practices

however are decreasing the seed germination rate,

causing an increase in pollution and waste. Trace

element analysis is a technique that measures very small

concentrations of specific elements present in a sample

to understand alteration of the host rocks under

investigation, with the greater purpose of reconstructing

fluid circulation of a hydrothermal system.

Microorganisms are vital to humans and the

environment, as they participate in the Earth's element

cycles such as the carbon cycle and nitrogen cycle, as

well as fulfilling other vital roles in virtually all

ecosystems, such as recycling other organisms' dead

remains and waste products through decomposition.

The majority of all oxidative sewage treatment

processes rely on a large range of microorganisms to

oxidize organic constituents which are not amenable to

sedimentation or flotation. Anaerobic microorganisms

are also used to reduce sludge solids producing methane

gas (amongst other gases) and a sterile mineralized

residue. In potable water treatment, one method, the

slow sand filter, employs a complex gelatinous layer

composed of a wide range of microorganisms to remove

both dissolved and particulate material from raw water.

Water chlorination is the process of adding chlorine to

water as a method of water purification to make it fit for

human consumption as drinking water. Water that has

been treated with chlorine is effective in preventing the

spread of waterborne disease. Chlorides are present

both in fresh and salt water and are essential elements

for life. A normal adult human body contains

approximately 81.7g chloride. Chloride increases the

electrical conductivity of water.

As a halogen, chlorine is a highly efficient disinfectant,

and is added to public water supplies to kill disease-

causing pathogens, such as bacteria, viruses and

protozoans, that commonly grow in water supply

reservoirs, on the walls of water mains and in storage

tanks.[1] The microscopic agents of many diseases such

as cholera, typhoid fever, and dysentery killed countless

people annually before disinfection methods were

employed routinely. Chlorine is obtained from salt

(NaCl). It is a gas at atmospheric pressures but liquefies

under pressure. The liquefied gas is transported and

used as such. As a strong oxidizing agent, chlorine kills

via the oxidation of organic molecules. Chlorine and its

hydrolysis product hypochlorous acid are neutrally

charged and therefore easily penetrate the negatively

charged surface of pathogens. It is able to disintegrate

the lipids that compose the cell wall and react with

intracellular enzymes and proteins, making them

nonfunctional. Microorganisms then either die or are no

longer able to multiply.

Water hardness is a natural feature and is a result of the

geology of the area, being primarily limestone.

Minerals such as calcium and magnesium dissolve into

the water as moves over and through the ground. The

level of these minerals in the water determines the

water hardness. The information in the table below

provides a general rule for classifying water hardness.

Hardness description Total Hardness in mg/l

Calcium carbonate

Soft < 150

Hard 150 – 300

Very Hard > 300