ON09-09-10 , AT DOHA, QATAR.

L & T Wastewater Treatment

O H M

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)

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

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/lBoth have its own advantages and disadvantages.

Commonly used Abbreviations

AP – Actuated Penstock ASP – Activated Sludge Plant DAF – Dissolved Air Flotation DC – Distribution Chamber DCU – Decanter Control Unit DO – Dissolved Oxygen DWF – Dry Weather Flow FDS – Functional Design Spec. FFT – Flow to Full Treatment FTE – Filtered Effluent FST – Final Settlement Tank FRC – Flow Reception Chamber GBT – Gravity Belt Thickener HMI – Human Machine

Interface OE – Odor Extract

OOSS – Out of Spec Sludge ORP – Oxygen Reduction

Potential MCC- Motor Control Center PA – Process Air PW – Potable Water RAS – Return Activated Sludge RL – Return Liquor SAS – Surplus Activated Sludge SDC – Strom Distribution

Chamber TSS – Total Suspended Solids STW – Sewage Treatment

Works TTP – Tertiary Treatment Plant TE – Treated Effluent WW – Wash Water

Wastewater Treatment – OVER VIEW

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.

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.

PRIMARY TREATMENT

Grit removal- Sand particles and other grit are separated and the grit is classified through grit classifier, Vendor:-Grit King

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.

SECONDARY TREATMENT

Anoxic Phase – Filling the SBR with the EffluentMixing Phase – Mixing operation is doneReaction 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.

INLET SEWAG

E

SCREENS

GRIT REMOVAL

SBRSLUDG

E

EFFLUENT

PRIMARY TREAT SECONDARY TREAT

Screen skip Grit skip

Cont: Page#14

Cont: Page#19

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

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.

- 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.

SLUDGE

Raw Sludg

e

Sludge Thicken

r

SAS Balan- cing Tanks

Aerobic Digester Tanks

Cont. from page#11

De- waterin

g

Disposal

TREATMENT

Sludge thickening by DAF and Gravity system:-

SLUDGE -

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

TREATMENTSLUDGE -

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.

SLUDGE -

TERITARY TREATMENT-

Dewatering thickening by Centrifugal Process :-Pic’s of Dewatering by Flottweg HTS Decanter and

SIEMENS

DEWATERING

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 from

SBR/ASP

Sand Filters or UF Balancing

Tank

Treated

Sewage Tank

UltraFiltratio

nCont. from page#11 Plantation

TERITARY TREATMENT - EFFLUENT

Pic’s for Treated Effluent water Storage tanks. Ground Tank and Elevated Tanks

TERITARY TREATMENT - EFFLUENT

Treated water is reused in Road side plants & Cultivating Fields.

ENDTHANKS