Basic Operations of Waste Water Treatment nirgunaya@gmail.com

1. L & T Wastewater Treatment
ON
09-09-10, AT DOHA, QATAR.
OHM

2. INTRODUCTION
 Wastewater is the potable water of a community after it
has been used in Residential areas, Hotels, Industries
etc. and has been contaminated by various uses.
 Wastewater contaminants are composed of variety of
soluble organic (Ex:-Fatty acids, Detergents, Fecal etc),
insoluble organic (Ex:-Body waste and Food particles)
and inorganic substances (Nitrogen and Phosphorus).
 The contaminants constitute of the following.
 BOD-Biochemical Oxygen Demand
 TSS- Total Suspended Solids
 TKN-Total Kjehldhal Nitrogen (Nitrification and De-nitrification)

3. INTRODUCTION
 The process which alters, reduces and removes the
contaminants from water is called wastewater
treatment and is done to minimize pollution along
with odor control mechanism for large sized plants.
 Treatment is basically carried out in two major
biochemical environments and in three stages.
 Aerobic (In presence of Oxygen) & Anaerobic (In absence of Oxygen)
 Primary treatment is similar for both.
 Secondary treatment.
 Tertiary treatment

4. INTRODUCTION
 Aerobic (In presence of Oxygen)
 BOD – 500 mg/l
 TSS – 100-300 mg/l
 TKN- 170 mg/l
 T.Phos-98 mg/l
 Anaerobic (In absence of Oxygen)
 BOD – 1000-10000 mg/l
 TSS – 5000-15000 mg/l
 TKN- 500-1000 mg/l
 T.Phos-300-1000mg/l
Both have its own advantages and disadvantages.

5. Commonly used Abbreviations
 AP – Actuated Penstock  OOSS – Out of Spec Sludge
 ASP – Activated Sludge Plant  ORP – Oxygen Reduction
 DAF – Dissolved Air Flotation Potential
 DC – Distribution Chamber  MCC- Motor Control Center
 DCU – Decanter Control Unit  PA – Process Air
 DO – Dissolved Oxygen  PW – Potable Water
 DWF – Dry Weather Flow  RAS – Return Activated Sludge
 FDS – Functional Design Spec.  RL – Return Liquor
 FFT – Flow to Full Treatment  SAS – Surplus Activated Sludge
 FTE – Filtered Effluent  SDC – Strom Distribution
 FST – Final Settlement Tank Chamber
 FRC – Flow Reception Chamber  TSS – Total Suspended Solids
 GBT – Gravity Belt Thickener  STW – Sewage Treatment Works
 HMI – Human Machine  TTP – Tertiary Treatment Plant
Interface  TE – Treated Effluent
 OE – Odor Extract  WW – Wash Water

6. Wastewater Treatment – OVER VIEW

7. Wastewater Treatment – OVER VIEW
Primary treatment:
 To prevent damage to pumps and clogging of pipes, Wastewater is
passed thru mechanical raked bar screens to remove large debris and
small inorganic material (sand and gravel) are removed by Grit
removal.
Secondary treatment:
 Wastewater is mixed with controlled population of bacteria and ample
supply of oxygen, microorganisms digest the fine suspended and
soluble organic materials, thereby removing from wastewater. It
includes Activated sludge, Sludge thickening, Balancing tanks etc.
Tertiary treatment:
 Advanced treatment is used to remove color, metals, organic chemicals
and nutrients such as phosphorus and nitrogen.

8. PRIMARY TREATMENT
Primary treatment includes two steps.
 Screening-As wastewater enters the plant it passes through
vertical screens (6mm aperture), objects trapped are trashed to
skippers. Vendor:-Longwood Engineering.

9. PRIMARY TREATMENT
 Grit removal- Sand particles and other grit are separated and
the grit is classified through grit classifier, Vendor:-Grit King

10. SECONDARY TREATMENT
 After Primary treatment wastewater still contains high
concentrations of dissolved, small suspended solids and organic
materials. Wastewater enters for secondary treatment.
Secondary treatment includes following steps.
 Secondary treatment uses extended aeration system of Activated
Sludge process in SBR, settlement tanks and Aerobic digesters.
 When fresh sewage or wastewater is added to Settling Tank,
approx. 50% of the suspended solid matter will settle out in 1.5-2
hours and is called raw sludge.
 The major five steps involved in SBR are as shown below.

11. SECONDARY TREATMENT
 Anoxic Phase – Filling the SBR with the Effluent
 Mixing Phase – Mixing operation is done
 Reaction Phase – Influent flow is terminated and Air is blown
through the diffusers called aeration, mixing continues.
 Settle Phase – Effluent is allowed to settle, aeration & mixing stop.
 Decanting phase- Effluent and sludge are removed for further
treatment to Settlement tanks/Sludge or UF balancing tanks.
After this the flows are split into two, Effluent & Sludge treatment.
Screen skip Grit skip
Cont: Page#19
EFFLUENT
INLET GRIT
SCREENS SBR
SEWAGE REMOVAL
SLUDGE
PRIMARY TREAT SECONDARY TREAT
Cont: Page#14

12. SECONDARY TREATMENT
Wastewater and sludge are reacted over several hours in the
presence of air. The air is stopped and mixed liquor in the reactor is
allowed to settle in the settlement tanks

13. SECONDARY TREATMENT
 Liquid pressure increases at a certain depth with the mass
concentration of suspended solids. Total mass of suspended solids
increases with the thrust of the mixer until complete suspension is
achieved.
 Pic’s of Aeration system and Settlement Tank
 As a biological treatment ASP must provide min. Aerobic sludge age of
6 days.

14. SLUDGE - TREATMENT
 Surplus Activated sludge (SAS) is routed to Sludge Balancing
Tanks, (where sludge is allowed to settle) prior being transferred
to Sludge thickening.
 Sludge Balancing Tanks shall be aerated and mixed to maintain a
minimum of 0.5mg/l of dissolved oxygen in the sludge.
 SAS thickening can be done by DAF-Dissolved air flotation,
Gravity thickening, lime sludge thickening and mechanical and
rotary drum thickening. Vendor:- Westpalia separator
environmental systems.
SAS Aerobic
Raw Balan- Sludge Digester De-
Sludge cing Thickenr Tanks watering
Tanks
Cont. from page#11 Disposal

15. SLUDGE - TREATMENT
Sludge thickening by DAF and Gravity system:-

16. SLUDGE - TREATMENT
 Sludge thickening by Centrifugal Process and Belt thickner:-
 Thickened sludge is passed to Aerobic Digesters, where the Bugs (Bacteria
and micro-organisms in wastewater industry are called Bugs) were created
naturally.
 Large quantities of air is pumped into Aeration basins for Bugs to breathe

17. SLUDGE - TREATMENT
 Aerobic Digesters:- Complete Digestion occurs in Aerobic
Digesters from there the sludge is dewatered and disposed off.
 Pic’s of Aerobic digesters and Anaerobic digesters.

18. TERITARY TREATMENT-DEWATERING
 Dewatering thickening by Centrifugal Process :-
 Pic’s of Dewatering by Flottweg HTS Decanter and SIEMENS

19. TERITARY TREATMENT - EFFLUENT
 Decanted water is treated in Sand filters or Ultrafiltration
balancing tanks from there to Ultrafiltration plant.
 Pic’s for Sand Filters and Ultrafiltration plant.
Effluent Treated
Sand Filters or Ultra Sewage
from
UF Balancing Tank Filtration Tank
SBR/ASP
Cont. from page#11 Plantation

20. TERITARY TREATMENT - EFFLUENT
 Pic’s for Treated Effluent water Storage tanks. Ground Tank and
Elevated Tanks

21. TERITARY TREATMENT - EFFLUENT
 Treated water is reused in Road side plants & Cultivating Fields.

22. END
THANKS