Basics of ENVIRONMENT ENGINEERING
Pervious Layer :- The layers which allow the water to pass through them and contain quantities of water is known as Pervious Layer or Aquifers or Water Bearing Strata .
|Aquifer||Store & Yield|
|Aquifuge||No Store & No Yield|
|Aquiclude||Store & No Yield|
|Aquitard||Store & Little Yield|
Zone of Saturation :- The portion of the soil through which lateral movement of water take place.
Also called out-cropping of W.T.
Natural outflow of water to earth’s surface.
Surface Spring :- When aquifer is exposed in valley against vertical cut, surface spring formed.
Artesian :- When pervious layer is closed between two impervious layers and have too much hydraulic gradient then artesian formed.
Horizontal tunnel constructed at shallow depth along the bank of river to intercept the ground W.T.
It depends upon yield of sources, nature of soil & size of gallery.
Suitable for increasing the surface source supply in dry season.
YIELD OF A WELL
Rate at which water percolates into well under safe maximum critical depression head is called Yield of a well.
Expressed in Cum/Hour or Lit/Hour.
Depression Head or Infiltration Well :- Difference between depressed water level and sub-soil water table level.
The yield of surface stream may be obtained by Stream gauging method, Cross-section velocity method & Chemical method.
The yield of underground water may be obtained by Constant level pumping test & Recuperating test.
|Water supply project||20 to 30 years|
|Sewage treatment plant||15 to 20 years|
|Purpose||Water consumption (lit/c/p)||% of total consumption|
|Commercial & Industrial||50||20% to 25%|
|Hostel, School &||135|
|Fire||5% to 10%|
FOR FIRE DEMAND
Q = 1135 (P/5 + 10)
Q = 3182√ P
Q = 900 √P
Q = 5663√ P
ARITHMETICAL INCREASE METHOD
Suitable for old & large cities and towns which have stabilized.
GEOMETRICAL INCREASE METHOD
Suitable for young and rapidly develop cities.
Eutrophication of water bodies is caused by the excessive discharge of suspended solids.
Important element responsible for this = Phosphates.
Algae, protozoa, fungi causes colour, odour and turbidity.
Clay, silt, organic and inorganic matter causes turbidity.
The suspended impurities cause turbidity in water.
Source of epidemic.
The colour of water is due to colloidal impurities.
|Property of water||Property Because of this Reason in water|
|Hardness||Calcium & Magnesium chlorides, bicarbonates.|
|Alkality||Carbonates & Bicarbonates|
|Softening||Sodium chlorides, carbonate & bicarbonate|
|Acidity||Carbon dioxide & Hydrogen sulphide.|
|Taste & Odour||Chlorine & Ammonia|
Measured by ordinary thermometer.
Permissible temperature for domestic supply is 10℃ to 15℃.
Expressed in numbers of a platinum cobalt scale.
Permissible colour for domestic supply is 10 to 20 ppm.
Turbidity removal is only objective of water treatment plant, it should have following units :- Rapid mixing, Flocculator, Settling tank and Filter.
Due to presence of suspended and colloidal matter in the water.
Expressed in ppm on Silica Scale.
Permissible for domestic supplies is 5 to 10 ppm.
Low turbidity = Baylis Turbidimeter (< 50 ppm).
High turbidity = Jackson Turbidimeter (>50 ppm).
Turbidity value is measured by Turbidity meter & expressed in FTU.
TASTES AND ODOUR TEST
Due to presence of micro-organisms either dead or alive, dissolved gases & mineral substances.
Odour changes with temperature.
Tested at 20℃ to 25℃.
Odour measure by osmoscope. (po value)
|0||No perceptible odour|
|1||Very faint odour|
|5||Extremely strong odour|
Acid rains is because of SO2.
CO2 rise Atmospheric temperature.
Ozone layer destroyed by CFCs, CCL4, N2O.
Permissible for domestic not exceed 500 ppm.
Causes Hardness in water.
Due to presence of bicarbonates, sulphates, chlorides and nitrates of calcium & magnesium.
For drinking purpose, limit of hardness = 100 ppm.
For domestic purpose, limit of chlorides = 250 ppm.
Chlorine gives safety against photogenic bacteria.
For public supplies, limit of chlorine = 0.1 to 0.2 ppm.
Residual chlorine determined by starch iodide.
Calorimetric or electrometric method used to measure p-H value.
Limit of p-H value for public supply = 6.5 to 8.
IRON AND MANGANESE
Colour of manganese is Brown.
Limit of iron & manganese for public supply = 0.3 ppm.
Iron make water in Red colour.
For domestic purposes not be more than 0.05 ppm.
For domestic purposes not be more than 0.05 ppm.
Copper indicates pollution.
Copper Sulphate used to removes algae.
Not more than 3 ppm for Domestic purpose.
Limit of fluorine for domestic purposes = 1.5 ppm.
Limit of sulphate for domestic purpose not exceed 200 ppm.
Bacteria is Single celled organisms.
Useful Bacteria = Non-pathogenic.
Harmful Bacteria = Pathogenic.
Sphere shaped Bacteria = cocci.
Rod shaped Bacteria = bacilli.
Twisted rod shaped Bacteria = spirilla.
Aerobic Bacteria = Require oxygen.
Anaerobic Bacteria = Survive without oxygen.
Unicellular animals = Protozoa.
Total count of bacteria per cm3 for domestic purpose = 0 to 100.
B-COLI & E-COLI
Membrane filter technique is used for finding out B-coli & E-coli.
Screen kept inclined at an angle of 45℃ to 60℃.
Area of opening such that velocity not exceeds 0.75 to 1 m/s.
Total 70% of impurities are removed.
60% suspended & 75% bacteria removed.
Detention time = 6 to 8 hours.
Depth of tank = 3 m to 6 m.
Velocity = 5 mm/s or 30 cm/min.
SEDIMENTATION WITH COAGULANTS
Necessary when turbidity of water exceeds 45 ppm.
Detention time = 2 to 6 hours.
Common coagulant = Alum or Aluminium Sulphate.
Sand required in filtration not loose weight more than 5% when placed in hydrochloric acid for 24 hours.
Effective size of sand = 0.30 to 0.50 mm.
Uniformity Coefficient = 1.30 to 1.75.
Three types of filters:
1. Slow sand filter
2. Rapid sand filter
3. Pressure filter
Slow sand filter
Effective size of sand = 0.30 to 0.35 mm.
Uniformity Coefficient = 1.75.
Require large area = 100 to 2000 m2.
Rate of filtration = 100 to 200 lit/m2/hour.
Remove bacteria = 99%.
Remove turbidity = 50 ppm.
Used when loss of head = 1.2 m.
Cleaning period = 1 month to 3 month.
After cleaning, water not used for = 24 to 48 hours.
Used for town and villages.
Work under atmospheric pressure.
Coagulant is not used.
Cleaning of slow sand filter is done by scrapping off the top layer of sand and admitting water.
Rapid sand filter
Effective size of sand = 0.35 to 0.50 mm.
Uniformity Coefficient = 1.60.
Cleaning filter by Back washing.
Pressure higher than atmospheric pressure.
Rate of filtration = 3000 to 6000 lit/m2/hour.
Remove bacteria = 80% to 90%.
Remove turbidity = 35 to 40 ppm.
Used when loss of head = 2.5 m.
Cleaning period = 2 to 3 days.
Pressure higher than atmospheric.
Rate of filtration = 6000 to 15000 lit/m2/hour.
Best suitable for swimming pool, railway station, individual industries, private estates etc.
Disinfectant for drinking water is Chlorine.
Time of contact for chlorination should at least 20 min.
Amount of chlorine = 0.5 ppm.
Used for water having turbidity less than 20 to 30 ppm.
Chlorine added before any treatment.
Amount of chlorine = 0.2 to 0.5 ppm.
Reduces bacterial load on filters.
Chlorine add after all treatment.
Amount of chlorine = 0.2 ppm.
Contact period = 20 min.
Chlorine added more than one point.
Chlorine is added in excess of that required.
Amount of chlorine = 2 to 3 ppm.
Break point chlorination
Destroys completely all the disease bacteria.
Prevent growth of weed.
Removes taste and odour.
Removal of unwanted chlorine in water.
Commonly used chemicals:
The hardness due to calcium and magnesium carbonates or bicarbonates is known as Temporary Hardness.
Temporary Hardness removed by Lime Process.
The hardness due to sulphates, chlorides and nitrates of calcium and magnesium is known as Permanent Hardness.
Removed by Lime Soda Process (Reduced hardness up to 50 ppm) & Zeolite (Sodium Silicate) or Base Exchange Process (Reduced hardness to 0 ppm).
DISTRIBUTION OF WATER
Used to Regulate flow of water.
Located at point of low pressure.
Air Relief Valve
Used to admit air to the pipe line to prevent formation of vaccum.
Provided at summit.
Reflux or Check Valve
Used to prevent water to flow back.
Also known as Non-return valve.
Safety Valve or Pressure Relief
Used to released the excessive pressure.
Scour Valve or Blow of Valve
Used to drain off the water from pipe after closing supply.
Provided at Low points.
Used for tapping water from mains for fire extinguishing, street washing & flushing sewer lines.
Sewage :- Water mixed with organic and inorganic matter, fluid waste from houses.
Main Sewer :- Receives sewage from the collection system or Branch sewer.
Branch Sewer :- Receives sewage from Outfall sewer.
Outfall Sewer :- Receives sewage from Lateral sewer.
Lateral Sewer :- Receives sewage from House sewer.
House Sewer :- Receives sewage from houses.
Sullage :- Water from bathrooms, kitchens, washbasins etc.
Human excreta is Semi-liquid waste.
FORMULA FOR STROM SEWARAGE
Q = C A5/8
Q = C A3/4
Q = C A2/3
Dia. of Sewer should not be less than 15 cm & not more than 300 cm.
Self Cleaning Velocity of sewage to prevent setting down of sewage is 0.75 m/s.
Self Cleaning Velocity of sewer = 0.40 m/s.
Self Cleaning Velocity for large sewer = 0.60 m/s.
Sewer of diameter less than 600 mm, spigot and socket joint is used.
Sewer of diameter more than 600 mm, collar joint is used.
For the purpose of inspection and cleaning of sewer.
Located at all changes of direction.
Maximum distance between sewer is 300 mm.
Lower portion of manhole is working chamber.
Minimum diameter of man hole cover should be 50 cm.
Catch basin are located when the sewer are laid at very small gradient and the velocity of flow of sewage is less than the self cleaning velocity.
Used to hold and throw water into the sewer for the purpose of cleaning.
Provided for the purpose of ventilation of sewer.
To prevent the accumulation of dangerous explosive and corrosive gases like CH4.
Liquid waste carrying human excreta flow.
Liquid waste without human excreta flow.
Provided 1 m above roof level.
To preserve the water seal of trap.
To prevent the entry of foul gases in the atmosphere.
Made of non-absorbent material & have self cleaning velocity.
Suitable and economical for sewage disposal of human excreta.
Located 3 m away from the ground water supply.
Vent pipe is provided.
Form of circular or rectangular tank.
Not recommended by health authorities.
An under ground sewage system with treatment of sewage.
Combination of sedimentation and digestion.
Give good result in porous soil.
BIO-CHEMICAL OXYGEN DEMAND
The amount of oxygen required for biological decomposition of dissolved organic solids to occur under aerobic conditions and at a specified time and temperature is called Bio-chemical oxygen demand.
CHEMICAL OXYGEN DEMAND
The amount of oxygen required by sewage from oxidising agent known as chemical oxygen demand.
According to IS, 45 litre of water per person per day is provided in case of office.
The length of rectangular sedimentation tank should not be less than 4 times the width of the tank.
Dose of coagulant is controlled by worm wheel.
Disinfection of swimming pool water is by ozonisation.
To prevent formation of ‘Ice’ of chlorine, kept temperature 38℃ to 42℃.
Formation of ‘Ice’ of chlorine are formed at temperature below 10℃.
In orthotolodine test, safe residual chlorine for drinking water is indicated by yellow colour.
Bleaching Powder is hypo-chlorite of lime.
In bleaching powder, chlorine content = 30% to 35%.
Cast iron pipe joined by Dresser coupling joint.
Joint used in pumping stations flanged joint.
Dead end system :- Suitable for Area developed in haphazard way.
Ring system :- Suitable for Well planned cities only
Grid iron system :- Suitable for City with roads of rectangular pattern.
Water leak into sewer = Infiltration.
Water leak from form sewer = ex-filtration.
Also known as Dry method.
Different type of refuse are collected, carried and disposed off separately.
WATER CARRIAGE SYSTEM
Removes domestic sewage, industrial sewage & storm sewage.
Initial cost of construction of water carriage system is very low.
Stoneware sewers used in House drainage and lateral connection.
Concrete sewers used in Main sewer & Branch sewer.
Cast iron sewer is used in Outfall sewer.
For separate system, cross section recommended is circular.
For combined system, cross section recommended is egg-shaped.
Boning rod is used for checking the levels of sewer.
Anti-siphonage pipe is not required in single stack system.
Relative stability = oxygen available in sewage/oxygen required to satisfy one stage of B.O.D.
Trickling filters used in secondary treatment.
Biological action used in trickling filter.
In Primary Settling tank, suspended solids are reduced from 40% to 70%.
In Activated Sludge Treatment, 80% to 95% bacteria are removed.
Grit chamber changed after 2 weeks.
Aerobic bacteria action used in oxidation pond.
Multiplying factor = 1.8, to obtain the maximum daily water demand in relation to the average daily demand.
Multiplying factor = 1.5, to obtain peak hourly demand relation to maximum daily demand.
Multiplying factor = 2.7, to obtain peak hourly demand relation to average daily demand.
Water losses in water supply system = 15%.
Average rainfall is a figure which is average over period of 35 years.
Evaporation losses reduced by acetyle alcohol.
Water is Hard if Hardness > 300 ppm.
Water is Soft if Hardness < 75 ppm.
Fluorides causes disease in teeth.
Copper causes disease in lungs.
Lead causes blue baby disease.
Vibrio cholera present in faecal matter.
Settling velocity of inorganic particle in sedimentation tank follow stoke’s law.
Sedimentation remove particle having specific gravity = 1.20.
S.O.R of sedimentation tank = Q/B.L
Detention time for sedimentation tank = LBH/Q
Activated carbon is used in removing taste and odour.
Reverse osmosis & Electrodialysis reduce salinity of water.
Purpose of surge tank to protect pipe line against water hammer.
Imhoff cone used to measure setteable solids.
Working condition in Imhoff tank Anaerobic in upper part & aerobic in lower part.
Compare to river water, sea water contain 10% less O2.
Most of bacteria in sewage is saprophytic.
|Sewage sedimentation tank||1 to 2 hour|
|Oxidation pond||2 to 6 weeks|
|Septic tank||12 to 36 hour|
Maximum B.O.D removed by oxidation ditch.
Oxidation ponds treat sewage by algae & bacteria.
|Grit Chamber||2 min|
|Activated sludge plant||6 hour|
|Sludge digestion tank||20 days|
Ringlemann’s scale is used to measure density of smoke.