Category: ENV

# Relation Between B.O.D (Biochemical Oxygen Demand) And Time

## Relation Between B.O.D (Biochemical Oxygen Demand) And Time

At certain temperature, the rate of deoxygenation is assumed to be directly proportional to the amount of organic matter present in the sewage at that time.
dLt / dt = – K.Lt ………….(1)
 Relation Between B.O.D And Time

[Note: Minus sign indicates that the with the passage of time the value Lt of decreases]
Where, Lt = Organic matter present in sewage after t day from the start of oxidation in mg/lit.
t = Time in days , K = Rate constant.

Now find out the relation between B.O.D and time?
Integrating equation (1), we get
ഽdLt / Lt = ഽ- K. dt
or,
log Lt = – K.t + C ………..(2)
Where C is constant of integration .

When t = 0, Lt = L (say)
Now, substituting these in equation (2) we have,
log L = – K. (0) + C
Or, C = log L

Substituting this value of C in equation (2) we get
log Lt = -K.t + log L
Or, log (Lt/ L) = -K.t
Or, 2.303 log10 (Lt/ L) = -K.t
Or, log10 (Lt/ L) = – 0.434 K.t
Or, (Lt/ L) = (10)^(-0.434 k.t)

If Yt represents the total amount of organic matter oxidized in t days (i.e B.O.D), then we have
Yt = L- Lt = L [1- (Lt/ L)]
Or, Yt /L = L- Lt = 1- (Lt/ L)
Or, Yt /L = L- Lt = 1- (10)^(-0.434 k.t)
Or, Yt = L [1- (10)^(-0.434 k.t)

# 3 Difference Between Biochemical (B.O.D) and Chemical (C.O.D) Oxygen Demand

## 3 Difference Between B.O.D & C.O.D

Following are the 3 differences between B.O.D (Biochemical oxygen demand) and C.O.D (Chemical oxygen demand) are described below:

# What do You Mean Natural Resource

The efficacy and stability of an ecosystem remain constant through the flow of energy and matter through it.

## Natural Resource

We regard it as a natural resource, which is connected with the existence of this energy and material, the population and ecosystem. That is all the resources that can fulfill the physical and socio-cultural needs of human beings.

As the only main source of energy, the sun regulates natural resources and people directly or indirectly utilize this solar power to make people develop their mechanical civilization.

Some natural resources such as solar energy, water, air, food plants and animals that people collect directly from their environment.
But can not use iron, underground water, and other mineral resources directly.

It is the duty of modern people to know about the source, nature of these assets and the nature of the use because otherwise, the overuse and misuse of these assets will result in the destruction of thousands of years of civilization in the near future.

Keeping in mind the huge demand for resources in the coming days, we have to make appropriate plans.

Currently, conventional energy sources meet the demand for 90% of energy from coal, petroleum, natural gas, etc. So, there is a possibility of running out of these non-renewable resources in the near future. Should be more motivated to search and use for Non-renewable resources.

With the use of traditional energy sources and advanced technology, the demand for energy resources will be meet next time.

People need to be more aware of the use of resources. Reservation of assets is an important thing, which will help to meet the needs of the present and the coming days.

Types of Rainfall

# Primary and Secondary Air Pollutants- And Their Examples

Air pollutants can also be broadly classified into two general groups- Primary air pollutants and secondary air pollutants.

## A. Primary Air Pollutants

Primary air pollutants are those emitted directly from identifiable sources.

Examples of primary air pollutants:
1) Fine particles(less than 100 μ in diameter)
2) Coarse particles (greater than 100 μ in diameter)
3) Sulphur compounds
4) Oxides of nitrogen
5) Carbon monoxide
6) Halogen compounds
7) Organic compounds

## B. Secondary Air Pollutants

Secondary air pollutants are those which are produced in the air by the interaction among two or more primary pollutants,or by reaction with normal atmospheric constituent, with or without photo-activation.

Examples of secondary air pollutants:
1) Ozone
2) Formaldehyde
3) PAN (Peroxy acetyl nitrate)
4) Photochemical smog
5) Formation of acid mists (H2SO4) due to the reaction of sulphur dioxide and dissolved oxygen. when water droplets are present in the atmosphere

Objectives of Air Conditioning

What is Smog

# What is Smog?

## What is Smog

Smog is a synchronous of two words, smoke and fog. Smog can be of two types—Photochemical or Coal-induced.

• Photochemical Smog is caused by the interaction of some hydrocarbons and oxidants mainly (nitrogen oxides) under the influence of sunlight rise to dangerous peroxyacetyl nitrate (PAN).

• Its main constituents are nitrogen oxides, PAN, hydrocarbons, carbon monoxide and ozone.

• It reduces visibility, causes eye irritation, damage to vegetation and cracking of rubber.

• Modern smog (also called traffic smog) is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

• Coal induced smog consists of smoke, sulfur compounds and fly ash.