Lecture 1.3 Flashcards
quantity of oxygen needed to satisfy biochemical oxidation of organic matter in waste sample in 5 days at 20°C
5-day Bio-Chemical Oxygen Demand (BOD5)
A high BOD indicates the presence of excess
amounts of ________ _________
organic carbon
is a consequence of adding
wastes with high BOD values to aquatic
ecosystems
Oxygen depletion
The higher the BOD of a source of waste, the
higher the _______ _______ of that waste.
polluting power
Type of Waste BOD (mg/L)
Domestic Sewage
Vegetable Processing
Slaughterhouse wastes
Cattle Shed Effluents
200-600
200-5,000
1000 – 4,000
20,000
Standards for Liquid Waste
Effluent generated from hospital
Parameters
pH
Suspended solids
Oil and greases
BOD (3 days @ 27°C)
COD
Bio-assay test
6.5 – 9
100 mg/L
10 mg/L
30 mg/L
250 mg/L
90% survival of fish after
96 hours in 100% effluent
Goal in treatment BOD
to remove
organic
material,
human
pathogens, and toxic chemicals
➢Involves physical separation to lower the
BOD of the waste
Primary Sewage Treatment
in Primary Sewage Treatment Suspended solids are removed through
the use of ______ ____
settling tanks
waste matter such as faeces or dirty water from homes and factories, which flows away through sewers
sewage
Usually removes from ____________ of the
BOD from typical domestic sewage (percentage)
30% to 40%
Uses microbial degradation to reduce the
concentration of organic compounds
further
Secondary Sewage Treatment
Involves microbial processes which can be
aerobic or anaerobic
➢Involves microorganisms, thus extremely
sensitive to toxic chemicals
Secondary Sewage Treatment
Combined use of primary and secondary
treatment reduces approximately ____________ to
_____of the BOD
80% to 90%
Uses chemicals to remove inorganic
compounds and pathogens
Any practice beyond secondary
treatment
Tertiary Treatment
Designed to remove non-biodegradable
organic pollutants and mineral nutrients
such as nitrogen and phosphorus salts.
Tertiary Treatment
Activated carbon filters are commonly
used
Tertiary Treatment
Also known as stabilization ponds or
lagoons
Oxidation Ponds
Used for simple secondary treatment of
sewage effluents
Oxidation Ponds
Uses heterotrophic bacteria to degrade
organic matter in the sewage which
results in production of cellular material
and minerals
Oxidation Ponds
the oxidation ponds has the several process
this degrade organic matter in the sewage
and results in production of cellular material and minerals
after that
______ of ______
Allows further decomposition of the organic matter by producing oxygen
lastly
the _____
Replenishes the oxygen used by the
heterotrophic bacteria
Heterotrophic bacteria
Growth of Algae
Oxygen
Oxudation ponds must be
Disadvantages
➢ Should be_________ deep in order to support the algal growth
➢ Restricted to _________ climate regions because they are strongly influenced by seasonal temperature changes
➢ Tend to _____, due to the settling of the bacterial and algal cells formed during the decomposition of the sewage.
➢ Degradation is relatively ______ and the effluents containing the oxidized products need to be__________removed from the ponds
➢ Overall, oxidation ponds tend to be _________ and require ______ holding capacities and ____ retention times
< 10 ft
warmer
fill
slow
periodically
inefficient
large
long
➢ Simple and inexpensive
➢ An aerobic sewage treatment method in which the sewage is distributed by a revolving sprinkler suspended over a bed of porous material
Trickling Filter
iquid waste, partially or completely treated,
flowing out of a reservoir, basin, or wastewater
treatment plant (clue out)
effluent
