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CENTER OF EXCELLENCE IN URBAN DEVELOPMENT (DECENTRALIZED WASTEWATER MANAGEMENT & PUBLIC PRIVATE PARTNERSHIPS). Department of Civil Engineering IIT Madras, Chennai. DECENTRALIZED WASTEWATER MANAGEMENT. CURRENT STATUS IN INDIA.

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CENTER OF EXCELLENCE IN

URBAN DEVELOPMENT

(DECENTRALIZED WASTEWATER MANAGEMENT &

PUBLIC PRIVATE PARTNERSHIPS)

Department of Civil Engineering

IIT Madras, Chennai


DECENTRALIZED WASTEWATER MANAGEMENT


CURRENT STATUS IN INDIA

The wastewater generation increased from 7,000 mld in 1978-79 to 17,000 mld in 1994-95 in Class I cities.

39% of wastewater was treated in the year 1978-79.

But, in the year 2003, only 26% of wastewater generated in cities was treated

27 cities have only primary treatment facilities


The mode of disposal is:

indirectly into the rivers/ lakes/ ponds/ creeks in 118 cities;

on to the agriculture land in 63cities

directly into rivers in 41 cities.

in 44 cities, it is discharged both into rivers and on agriculture land.

In many of the coastal cities, the wastewater finds its way into estuaries, creeks, bays etc. (Around 25% of total wastewater)


PARADIGM SHIFT IN RECENT PAST

  • In the past, wastewater was a “problem”

  • Now, it is considered as a “resource”

  • Example:

    • “Newater” scheme in Singapore

    • Treated domestic wastewater for Industrial use

    • “Zero Discharge” norm for major industries

    • “Recycled water” for domestic use

    • Treated wastewater for groundwater recharge & irrigation

Zero Discharge


ISSUES TO BE ADDRESSED

  • To develop tailor made treatment processes for various situations

  • Wastewater treatment, reuse and recycle

  • Life cycle analysis of wastewater treatment systems.


How can we solve the problem..

  • Develop “Tailor Made” wastewater treatment processes for various situations

    • Decentralized, economically viable and environmental friendly technologies

      • Pond systems

      • Constructed wet lands

      • Phyto-remdiation systems

      • Biofiltration and sand filters

      • Septic Tanks

      • Biomembrane processes

      • Biotowers

    • Selection of the systems depends on soil and groundwater conditions and availability of land


  • Pond systems

  • Phyto-remdiation systems

  • Constructed wet lands


  • Biofiltration and sand filters

  • Septic Tanks

  • Biomembrane processes


Aerobic processes


Anoxic processes


Anaerobic processes


Combined aerobic, anoxic, and anaerobic

processes


Ponds and Lagoons

Sewage Contains

  • Pathogens or disease-causing organisms

  • Water, with only 0.06 percent of the dissolved and suspended solid material.

  • Suspended particles present in untreated sewage ranges from 100 to 350 mg/l.

  • Pathogens or disease ranges from 100 to 350 mg/l.

  • Sewage also contains nutrients (such as ammonia and phosphorus), contains nutrients (such as ammonia and phosphorus),

  • Ammonia can range from 12 to 50 mg/l and phosphorus can range from 6 to 20 mg/l in untreated sewage.


Lagoon processes


Lagoons

  • Like most natural environments, conditions inside facultative lagoons are always changing.

  • Lagoons experience cycles due to variations in the weather, the composition of the wastewater, and other factors.

  • In general, the wastewater in facultative lagoons naturally settles into three fairly distinct layers or zones.

  • Different conditions exists in each zone, and wastewater treatment takes place in all three


Lagoons…

  • The top layer in a facultative lagoon is called the aerobic zone, because the majority of oxygen is present there.

  • How deep the aerobic How deep the aerobic zone is depends on loading, climate, amount of sunlight and wind, and how much algae is in the water.

  • The wastewater in this part of the lagoon receives oxygen from air, from algae, and from the agitation of the water surface (from wind and rain, for example).

  • This zone also serves as a barrier for example). This zone also serves as a barrier for the odors from gases produced by the treatment processes occurring in the lower layers.


Preliminary treatment

  • Things like rags, sand, gravel and larger pieces of organic matter must be removed before it enters the Treatment System.


Aerial View of a Lagoon System


Advantages and Disadvantages

Advantages

  • Inexpensive and Reliable system in tropical countries

  • Min operation and maintenance

  • No energy requirement

    Disadvantages

  • Requirement of large area

  • Odor and rodent problem

  • Effluent with high total BOD


Constructed Wetlands


Removal Mechanisms

Wetland treatment:

Organic matter, TSS, N, P, pathogens

  • Removal mechanism:

    • Biological:

      • microbial degradation

      • plant uptake

    • Physico- chemical:

      • adsorption

      • sedimentation

      • precipitation


  • Organic Matters

    • Sugars, Proteins, lipids;

    • Toilet wastes, cleaning, food wastes

Microorganisms

Pollution

Biomass + breakdown products

(Sludge)

Aerobic (with oxygen)

Anaerobic (without oxygen)


Nitrogen removal

Proteins

ammonia-N

nitrification

autotrophic- aerobic

nitrate- N

denitrification

heterotrophic- anaerobic

N2 gas

  • Plant uptake

  • Ammonia volatilization

  • Storage in detritus and sediment


Phosphorous removal

Phosphorous adsorption:clay-humus complex

Phosphorous precipitation:iron, aluminum, calcium

Problems:saturation and clogging

Plant uptake


Pathogens

  • Sedimentation / filtration

  • Natural die-off

  • Excretion of antibiotics from roots of macrophytes


Plants

The role of the plants:

  • The root system increases the surface available to bacterial colonisation;

  • Transfer oxygen to provide an aerobic/oxidized environment, oxygen leakage from the roots( limited);

  • Nutrient assimilation (N and P) (limited);

  • Maintain hydraulic pathways in the substrate;

  • Plant litter provides substrate to the microorganisms;

  • Accumulated liter serves as thermal insulation;

  • Aesthetics of the wastewater treatment plant.


Plants

  • A wide variety of aquatic plants can be used.

  • Selecting plants:

    • Native plants;

    • Active vegetative colonizers;

    • Considerable biomass, stem densities;

    • Sometimes a combination of species.


Wastewater treatment

Primary treatment :

Septic tank :lower the total organic loading, and separate the solids from the liquid

Secondary treatment:

Constructed wetland:convert the dissolved or suspended material into a useful form separated from the water


Vertical subsurface flow

Floating Macrophytes system

Constructed wetlands: Different types


Aerobic Suspended Growth Systems(s32)


Process Description

The aerobic conversion of the organic matter occurs in three steps:

  • Oxidation

  • COHNS + O2 + BACTERIA  CO2 + NH3 + END PRODUCTS+ ENERGY

    (Organic matter)

  • Synthesis of new cells

  • COHNS + O2+ BACTERIA + ENERGY  C5H7NO2

    (new cells )

  • Endogenous respiration

  • C5H7NO2 + 5O2  5 CO2+ NH3+ 2H2O + ENERGY


Pathways for the breakdown of organic matter


Extended Aeration System

External substrate is completely removed.

Auto oxidation (internal substrate is used)

Net growth = 0


  • Advantages

  • Sludge production minimal

  • Stabilized sludge  No digesters are required

  • Nutrient requirement minimal


  • Disadvantages

  • High power requirement

  • Large volume of aeration tank

  • Suitable for small communities


Oxidation ditch – Pasveer Ditch


  • Attached Growth systems

  • Aerobic

    • Trickling filters

    • Rotating biological contactors

  • Anaerobic

    • Anaerobic filters

    • Denitrification systems


System biology - Heterogeneous microbes


  • Rate of organic matter removal

  • Wastewater flow rate

  • Organic loading rate

  • Rate of diffusivity of food and oxygen into the biofilm.

  • Temperature


Trickling Filters

T.F  Reactor in which randomly packed solids forms provide surface for microbial growth.

- system for wastewater distribution

Specific surface area and porosity

Specific surface area: The amount of surface area of the media that is available for bio film growth


RBCs


Membrane Bioreactors

  • Employ biological reactor and membrane filtration as a unified system for the secondary treatment of wastewater

  • Membranes perform the separation of the final effluent from the biomass through filtration

  • Filtration takes place by the application of a pressure gradient


discharge

DN

N

SCT

conventional technology

membrane technology

effluent

UF not

Sec. Clarif.

SS

Nitri

Deni

Process Basics

SS


sludge floc

membrane

suction

bacteria

water

kinet. energy

dis. solids

viruses

Process Basics


Back pulse

Module

Permeate

Cleaning

chemicals

ZeeWeed

Aeration

effluent

aeration

BP Tank

Submerged MBR System

Feed

Re-circulation

SS


Assessment of MBR Technology

  • Advantages

    • High effluent quality

    • No sludge settling problems

    • Reduced volume requirements

  • Disadvantages

    • Membrane fouling

    • Increased operational costs


Space Requirement

  • Many Compact Units are available


For Sustainability

1. Promote Anaerobic treatment technologies for energy generation

  • Less energy intensive

  • Can generate alternate energy

  • So far not very successful due to the lack of information about the process

    • Demonstration plants

    • Operational guidelines

    • Training in design, maintenance and operation


2. Develop Wastewater reuse and recycle systems after adequate treatment

  • Wastewater is not a problem, but a resource

  • Treat the waste according to the beneficial use

    • Agricultural - Preserve as much nutrients as possible, kill the pathogens (low cost technologies)

    • Industrial – Higher degree of treatment- (bio membrane processes)

    • Domestic – Flushing toilets, gardening etc…

    • Groundwater Recharge- needs high end treatment if the GW table is high, otherwise the soil will act as a treatment unit..

    • Base flows in Rivers – Needs treatment based on the carrying capacity of the existing river, water body


Wastewater reuse applications


Wastewater reuse applications


Selection of Treatment Technologies

  • Life cycle analysis of wastewater treatment systems

    • The treatment system should be

    • Economically viable, Environmentally Friendly, and Sustainable.

    • Many times these factors are not being considered.

  • Develop guidelines for life cycle analyses of wastewater treatment systems.

    • Pros and cons of the systems

    • Eg: Energy consumption, Residual pollution left over, Environmental degradation, contribution to global warming etc..


Thankyou


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