environment Flashcards
impacts of suspended solids in raw water?
- growth of disease causing micro-organisms
- aesthetically displeasing
- provides adsorption surface, interfere with chlorination
- incrustation of pipes
apparatus used for measuring suspended solids and acceptance limits?
muffle furnace
500 mg/l, 2000 mg/l
turbidity measuring methods and reference chemical
turbidity rod method -pt niddle, Si02 Jackson turbidity method -lighting candle, (0-25) JTU Baylis turbidmeater -color matching , absorption principle 0-2 NTU Nephlometer (0-1) NTU - scattering principle, formazene is used - FTU or NTU is unit, 1 NTU- 10 NTU
color measurement and limits
TinTometer
color matching technique, chloroplatinate ion
5 TCU - 25 TCU
measurement of alklinity
titration with 0.02N H2SO4
1 ml for 1mg of alklinity as CaCO3
ph 10 to 8.3 : Oh, 1/2 CO3 , phenopthelene indicator
ph 8.3 to 4.5: HCO3, 1/2 CO3, methyl orange
Limits 200 mg/l, 600 mg/l
Ph levels for drinking water
07 -8.5
6.5-9.2
corrosion and incrustation
number of rapid sand filter bed by Morell and Wallace equation
flow rate and depth and size of medium
N= 1.22 sqrt(Q) + 1(stndby)
Q - discharge in MLD
back-washing 45cm/min [6-16 X flow]
depth = (60-90 cm) & size=(0.35-0.55 mm)
R.O.F = 3-6 m/hr = 30 times slow sand
settling velocity of non laminar particle
if d > 0.1 Vs = [4/3 g.d.(G-1) /Cd ]^0.5 Cd= 0.4 for Re > 10^4 Cd= 24/ Re for Re<0.5mm Cd = 24 /Re + 3/sqrt(Re) +0.34 for transition
example applied??
effective height of stack
dH = [1.5 + 2.68PD *(Ts -Ta)/Ts] DVs /u
P ~ 1
T in kelvin
Factors to be considered in the design and operation of a sanitary landfill site
-Access to the site
-Cell design and construction
collection of gas and lechate
water table
-Cover material
1 Cum soil for 4~6 Cum of refuse
clayey soils are preferred
-Equipment’s required
earth movers
-Fire prevention
separations and water availability
-Land area
minimum 1 year dump, preffrable 5~10 years
-Land filling method
-Litter control
-Unloading Area
should be kept small, generally under 30 m.
-Drainage arrangements
drainage ditches shall be installed
1~2% surface slope must be there
INDORE meathod of refuse disposal
- manual turning of piled up mass for its decomposition under aerobic conditions.
- layers of vegetable wastes and night soil are alternatively piled in depths of about 7.5 to 10 cm each, to a total depth of about 1.5 m in a trench; or above the ground to form a mound called a windrow.
- The mixture is kept aerobic by turning regularly for 2 to 3 months.
- This compost mass is then left for another about 1 to 1½ months without any turning; after which, the compost becomes ready for use.
- The entire process thus takes about 4 months.
Design of manifold lateral under drainage of rapid sand filter
Area of perforation = 0.2% x Area of filter Area of each lateral = 2 x Area of perf. Area of manifold. =2 x Area of lateral Find Dia of manifold assume spacing of laterals as 15 cm No of laterals = L / 0.15 Length of laterals = 0.5*[L -D] assume dia of perforation = 6 mm find No of perforation in all laterals N = Area of all perf /Ap1 find Area and dia of each lateral Check Lateral.Length/Dia.lateral <60
back-washing check:
velocity in laterals and manifolds < 2.4 m/s
four mechanisms of coagulation
1. ionic layer compression (van der waal's force vs zeta potential) 2. adsorption and charge neutralization (aqua metallic ions or hydro-oxides) 3. sweep coagulation 4. inter-particle bridging
blade floculator design points
P = F.V
P=μ.V.G^2
Cd = 1.8 for flat blades
V = 75% of blade center Velocity
oxidation pond design characterstics
detention time = 2~6 week OLR = 150 kg/ha/day depth = 1~ 1.8m only area of unit = 0.5~1 acre pathogen removal= 99% BOD removal = 95%
design of inlet pipe
v=0.9m/s, [Q =VA]
D.outlet = 1.5 D.in
environmental impact assessment
prepared and submitted along DPR
compulsory by GOI in all projects
Methodology
1. Impact identification
checklist, matrices, networks, activity and connected impact
2.Prediction of E.Impact
greatest degree of scientific application, real impacts of proposed development by performing calculations
3. Evaluation of impact
conversion of impacts in a comparable units and normalization.
conversion in monetary values to make it comparable with other cost and benefit of project
KMnO4 points
- water contaminated with lesser amount of bacteria is treated
- helps in oxidizing taste producing organic matter
- used as an algicide and for removing color and iron
- normal dose for disinfection 1-2 mg/L ,contact period 4-6 hrs
- 48 hrs dont use water
- kills 98% bacteria and 100% cholera virus
- dark brown precipitate
COD for glucose solution
180 g glucose + 196 g of O2
plume behavior coming out of stack
Looping= super adiabatic + strong wind
Neutral = upward vertical= near adiabatic + no wind
Coning = near adiabatic + winds
fanning =(horizontal)= negative adiabatic + wind
Lofting = inversion + super adiabatic + wind
Fumigating = super adiabatic + inversion + wind
Trapping = inversion+adia+ inversion + wind
various processing tehniques used in solid waste management
mechanical volume reduction (1100kg/cu.m)
thermal volume reduction
manual components separationx,
Land fill area method & Depression method & Trench method
Area method
- when area is unsuitable for excavation of trenches
- earthen levee is built first
- thickness of compacted waste 2-3 m
- 150 to 300 mm layer of cover material is placed over the completed fill
- completed lift including cover is called cell
trench method
- adequate depth of cover material is available & water table well below
- dragline or more scrappers are used
Depression method
- location where artificial or natural depression exist
canyons, ravines, dry borrow pits quarries
points on sanitary composting
- aerobic “INDORE PROCESS”
(2~3 months) mixing of refuse is ensured
left for 1.5 month - layers of vegetable waste and night soil are piled up alternatively 7.5cm and 10cm to a total 1.5 m
- anaerobic “BANGLORE PROCESS” (4~6 months)
- covered over by 15 cm earth and left
- decomposition start in 3-4 days and temp ~75 C
- end product is humus/manure/compost
- optimum C/N ratio = 30 to 50
Fire demand formulas
National board of Fire underwriters
Q = 4367 sqrt(P)[1 -.01*sqrt(P)]
P= population in thousands
Q= discharge in Ltr/minute
Kuchling’s formula
Q = 3182 *sqrt(P)
Freeman formula
Q= 1136 *[P/10 +10]
Buston’s formula
Q= 5663 * sqrt(P)
Control of Gas movement in landfill sites
By vents and barriers - gravels and clay
By gas recovery - gas recovery wells
Control of leachate Movement in land fill sites- geotextiles and clay
secondary air pollutants
- Sulphuric acid
- Ozone
- Formaldehydes
- Peroxy-acyl-nitrate (PAN)
Socket and Spigot Joint
- sometimes called bell and spigot joint
- are made in such a way that one of their end is enlarged, whereas the other end is normal. The enlarged end is called “socket” or “bell”, while the normal end is called “spigot”.
- A few strands of jute are wrapped around the spigot before inserting it into the socket (or bell) and then, more jute is packed into the joint. The remaining space between the socket and the spigot is finally filled with molten lead
- This type of joint is some what flexible and allows the pipes to be laid on flat curves without the use of any other special material.
- skilled labour is required for this type of joint.
Imhoff tank
Imhoff tank is an improvement over septic tank, incoming sewage is not allowed to get mixed with the sludge produced and outgoing effluent is not allowed to carry large amount of organic load
- detention period is less
- combines the advantage of of both the septic as well as well sedimentation tank
- economical to operate
- dont require skilled attention
- 60-65% removal of solid
- 30-40% removal of BOD
- no problem of sludge disposal as in case of sedimentation tank
- depth is more , which makes the construction costlier
- unsuitable when sewage is highly acidic
- tendency to foam or boil
standard rate trickling filter (SRTF) operational troubles
fly nuisance- flies can chock the filter, this can be avoided by DDT spray
Odour Nuisance: it happen in fixed nozzels, H2S and other gases, remedy- chlorinate the water
Ponding Trouble: due to heavy growth of algae and fungi , remedy - chlorine or CuSO4
design points of septic tank
- detention time = 24 - 48 hrs
- A minimum depth of sedimentation should be 25 to 30 cm.
- accumulation of sludge = 30 L/cap / year
- 30 cm freeboard
- 1.5 m height(assumption)
grit chamber points
- to remove inorganic particles of .15-.20 mm or more
- these particles could clog the channel and damage
pumps - flow velocity should not be low to settle organic material
- detention time 30 to 60 sec
- proportional weir or sutro weir is provided at lower end of rectangular grit chamber
Moving Bed Biofilm Reactor (MBBR)
- This process uses small, plastic elements (on the order of 7 to 22 mm effective diameter) to support the growth of bio-film in the rector.
- The suspended growth portion of the hybrid is designed as a complete mix reactor.
- The process does not use a return sludge flow.
- The media (typically polyethyle) is formed in a geometry to provide a high surface area (250-515 m2/m3).
- It has a density near to that of water ( 0.96 g/cm3).
- The reactors are normally filled from one-third to two-thirds of their empty volume with media.
- Because of their shape, less than 15 percent of the water is displaced.
- A screen across the outlet is used to prevent the media from leaving the aeration tank.
- Aeration is typically by coarse bubble diffusers.
The LN concept:
The LN concept: The parameter LN is a statistical measure indicating how frequently a particular sound level is exceeded.
The value of LN will represent the sound pressure level that will exceed for N% of the gauging time. Say for example, the given 70 dB value of L60 will mean that the sound level will exceed 70 dB for 60% of the measuring time.
sewage sickness
In sewage farming, when sewage is applied continuously on the agricultural land, the voids of soil go on clogging gradually. A time comes, when the soil voids get completely clogged, air circulation through the soil is totally stopped and sediments get deposited on the surface. An anaerobic condition is developed. At this stage, the soil is unable to absorb further sewage load. An insanitary condition is developed by liberating
bad smell. Such condition is termed as sewage sickness.
The following measures may be taken to prevent sewage sickness :
(i) The primary treatment should be given to sewage to eliminate the suspended solids.
(ii) The intermittent supply of sewage should be adopted considering the nature of soil.
(iii) Crop rotation system should be followed so that the different crops may consume different fertilizing elements.
(iv) The sub-soil drainage system should be provided to drain out the subsoil effluent.
(v) Deep ploughing by tractor should be adopted to increase the soaking capacity of soil.
(vi) Time to time, a thin layer of surface soil should be removed by scrapping.
self purification IMP problem formulas
[L/(Dc.f)]^(f-1) = f[1- (f-1)(Do/L)]
can find Dc or L from that
Dc =L *[10^(-kd.Tc) ] , can find Tc from here
What do you understand by sludge digestion? Briefly explain the distinct stages
of sludge digestion and the factors affecting the sludge digestion.
Sludge Digestion: The sludge is withdrawn from sedimentation basins contains a lots of putricible organic matter that if disposed of without treatment may cause evolution of foul gases and hazardous
to environment. This sludge is thus stabilized by decomposing the organic matter under controlled
anaerobic conditions. This process is called sludge digestion.
(ii) Various stages of sludge digestion are:
(a) Acid fermentation: This is the first stage of sludge digestion in which sludge is to be acted upon by acid formers (anaerobic & facultative bacteria). These
organisms solublize organic solids through hydrolysis is to form volatile acids and organic alcohols along with evolution of gases like CO2 , CH4 or SO2 etc.
(b) Acid-regression stage: In this intermediate stage, the volatile organic acids and nitrogenous compounds of previous stage are converted to acid carbonates and ammonia compounds with help of bacteria. Evolution of H2S & CO2 is there but not so significant.
(c) Alkaline Fermentation stage: In this final stage, more resistant materials like proteins are attacked and broken up by bacteria called methane formers. Ammonia, organic acids and gases are by-products. The liquid separates from solids and digested sludge is produced.
In first two stages pH is below 7 and medium is acidic however the medium changes to alkaline in final stage.
