Wastewater treatment process | Important Questions on Primary Treatment of Sewage

Primary treatment consists solely separating the floating materials and also the heavy settable
organic and inorganic solids. It also helps in removing the oils and grease from the sewage.
This treatment reduces the BOD of the wastewater by about 15 to 30%. The operations used
are screening for removing floating papers, rages, cloths, etc., grit chambers or detritus tanks
for removing grit and sand, and skimming tanks for removing oils and grease; and primary
settling tank is provided for removal of residual suspended matter. The organic solids, which
are separated out in the sedimentation tanks in primary treatment, are often stabilized by
anaerobic decomposition in digestion tank or incinerated. After digestion the sludge can be
used as manure after drying on sludge drying beds or by some other means.

SOME IMPORTANT QUESTION ON "PRIMARY TREATMENT OF SEWAGE"

1.Define humus tank?

The efficient of the filter is therefore, passed through a sedimentation
tank called Humus tank otherwise called secondary clarifier or
secondary settling tank.

2. What are the distinct stages in the sludge digestion processes?

1) Acid fermentation
2) Acid repression
3) Alkaline fermentation

3. Define the term ripened sludge?

This digested sludge (geHong from Alkaline fermentation stage)is
collected at the bottom of the digestion tank and is also called repented
sludge.

4. What are the factors affecting sludge digestion?

1)Temperature Thermopolis Metropolis
2. Pit value
3. Seeding with digested sludge
4. Mixing and stirring of the raw sludge with digested sludge.

5. What are functions of aeration in ASP?

1) oxygenation of the mixed log wor
2) Flocculation of the colloid in sewage influent
3) Suspension of activated sludge

6. What are the methods employed for the purpose of certain in ASP?

i) Diffused air aeration air aeration
ii) Mechanical aeration
iii) Combined diffused air and Mechanical aeration

7. What are the patterns of mechanical aeration?

i) Haworth paddle or Sheffield aeration system
ii) Hartley paddle or bir Mangham Bio flocurelation system
iii) Simplex aeration system
iv) Link belt aeration system
v) Kessner Brush aeration system

8. List out the important aeration processes in the ASP?

(1) Conventional process
(2) Tapered aeration process
(3) Step aeration process
(4) Contact stabilisation process
(5) Completely mixed process
(6) Modified aeration
(7) Extended aeration

9. What are the advantage of stabilization ponds?

1. Lower initial lost than required for a mechanical plant.
2. Tower operation costs
3. Regulation of efficient discharge possible their provoking control
of collection during critical times of the year.

10. What are the disadvantages of lagoons?

1) Requires extensive land area. Hence the method can be used
only on rural area.
2) If used in urban areas, expansion of town and new developments
may encroach on the lagoon site.

11.What do you understand by facultative ponds?

(1) A facultative panel combine the features of the aerobic and
anaerobic ponds.
(2) Constructed of intermediate depth (1, to 1.5m)
(3) A facilitative bond consists of three
(i) An aerobic Zone --Top
(ii) Facilitative zone
(iii) Anaerobic zone --bottom

12.What are remedies measurement for rising sludge problem?

I) Increasing the return sludge age
II) Increasing the speed of the sludge scraper mechanism, where
possible
III) Decreasing the mech cell residence come by increasing the
sludge write rate

13.What is meant by sludge bulking?

Sludge with poor setting characteristics is termed bulking sludge. It
results on poor influent due to the presence of excessive suspended
solids and also in rapid loss of MISS from tance aeration

14.What are the advantage of intermittent and filters?

(i) The efficient from intermittent sand filter is of better quality. It is
more clean and more stable and hence does not need further
treatment before disposal
(ii) The filter work under aerobic conditions, and hence there is no
trouble of odour, flies and insects
(iii) The operation is very simple, requiring no mechanical
equipment except for dosing

15.What are the disadvantages of intermittent sand filters?

i) The rate of filtration and hence that of load long is very small per
unit surface area of the filter hence they cannot be employed for
medium size or bigger plants
ii) They requires large area and large quantity of sand due to which
their construction is very lostly.

16.What do you understand by contact beds?

Contact beds, also called contact filters, are similar to inter mitten sand
filters in construction, except that th filtering media is very coarse,
consisting of broken stones called ballast of 20 to 50mm gauge.
A contact bed is a water tight take of masonry walls and of rectangular
shape.
The depth of filtering media is kept b/w 1 to 1.8m

17.What are the operations involved in the contact beds?

1. filling
2. Contact
3. Emptying
4. Oxidation

18.What are the advantage of contact of beds?

i) Contact beds can work under small heads.
ii) Contact beds can be operated without exposing the sewage
efficient to view.
iii) There is no nuisance of filter flows
iv) The problem of odour is much less as compared to trill long filters.

19.What are the disadvantage of contact beds in T.F?

i) Rate of loading is much less in comparison to trickling filters.
ii) Large areas of land is required for their installation
iii) intermittent operation requires continceoces attendance
iv) The cost of contact beds is mech more as compared to trick long
filters.

20.What do you mean by tracking filters?

Trickling filters, also as percolating filters or sprinkling filters or sprinkling
filters are similar to contact beds in construction, but their operation is
continuous and they allow constant aeration In this system sewage is
allowed to sprinkle or trickle over a bed of coarse, rough hard filter media
and it is then collected through the under drainage system

21.What are the purpose of under drainage system?

The purpose of under drainage system is two fold
(i) to carry away the liquid efficient and sloughed biological solids.
(ii) To distribute air through the bed

22.What are the merits of conventional trickling filter?

1) The efficient obtained from trickling filters is highly nitrified and
stabilized. The efficient can therefore be disposed of in smaller
quantity of deputation water
2) It has good dependability to produce good efficient under very
widely varying weather and other conditions
3) The working of trickling filter is simple and sheep and does not
require any skilled supervision.

23.What are the demerits of conventional trickling filters?

1) The loss of head through the filter system is high their making the
automatic dosing through siphonic doing tank necessary
2) The cost of construction of the filter is high
3) They require large area in comparison to their biological treatment
processes.

24.What is the necessary of Recirculation in T.F?

Recirculation is necessary to provide uniform hydraulic loading as well as
to dilute the high strength waste waters. In constant to the low rate filters,
in high rate filters a part of settled or filter efficient is recycled through the
filter.