Environmental Studies: Science and Engineering

ByDr. Anurag Garg

28 February 2011

Course Outline

• Solid and hazardous waste management• River, lake and groundwater pollution• Principles of water and wastewater treatment

References• Cunningham W.P. and Cunningham M.A. (2002), Principles of Environmental Science, Tata

McGraw-Hill Publishing Company, New Delhi.• Nathanson, J.A. (2002), Basic Environmental Technology: Water Supply Waste

Management and Pollution Control, 4th Ed. Prentice Hall of India, New Delhi.• Masters, G.M. (2004), Introduction to Environmental Engineering and Science, Prentice-Hall

of India, Second Indian Reprint. • Davis, M. L. and Cornwell D. A. (1998), Introduction to Environmental Engineering, 2nd Ed.,

McGraw Hill, Singapore. • Wright, R.T. (2007), Environmental Science: Towards a Sustainable Future, 9th Ed, Prentice

Hall of India, New Delhi.• Supplementary Reading Materials (Selected Book Chapters and Papers)

Weightage: 33 marks; End sem: 20 marks; Quizz/ class performance: 13 marks

What is Sustainable Development?• Is a development that meets the needs of the

present without compromising the ability of future generations to meet their needs.

• Sustainable development is a way of improving or advancing our culture in a way that can be maintained over the long haul.

• Sustainable development is a means of meeting present needs in ways that do not impair future generations – and other species – from meeting their needs.

Sustainable Development

Environment Economic

Social

Traditional decision making Decision making in a sustainable society

Sustainable development requires strategy that satisfy social, economic and environmental goals simultaneously.

Operating Principles of Sustainable Development

• Stabilize our population

• Better manage how we grow

• Use resources much more efficiently

• Clean, renewable energy supplies

• Manufacture a large portion of our goods with recycled materials

• Restore natural systems

Matrix Showing The Systems and Principles of Sustainability

Principles of sustainable developmentSystems

Conservation (efficiency and frugality)

Recycling and composting

Renewable resource use

Habitat protection, restoration and sustainable management

Growth management

Transportation Buy fuel –efficient car

Housing and other buildings

•Build home using recycled materials•Build a compost bin

•Build compact cities•Create urban growth boundaries

Agriculture, food processing and distribution

•Use biodiesel in farm machinery•Install wind generators

Business Protect native vegetation

Zero Waste Communities

• Reduction in the extraction of new resources and reducing waste at the source by designing products that are non-toxic and can be reused, repaired, or recycled back into nature or back into the marketplace and stimulating the marketplace to use those materials.

• Seeks to redesign the products

• Zero waste concept transforms a liability (waste) into an asset (resources) that yields local economic benefits.

The Process Chain

• The key to achieving Resource Management is ensuring effective operation of the process chain over the lifecycle of goods and services –sourcing of raw materials, design, manufacture and consumption

Examples for Zero Waste Communities

Examples for Zero Waste Communities…..

Environmental Studies: Science and Engineering

ByDr. Anurag Garg

1 March 2011

• The term municipal Solid Waste (MSW) is generally used to describe most of the non-hazardous waste from a city, town or village.

• MSW comprises – Residential, – Commercial, – Institutional,– Industrial (not from the process) waste– Construction & demolition waste

Municipal Solid Waste (MSW)

Major Components of MSW

MSWRefuse Trash

Garbage and rubbish Bulky material

The quantity of MSW generated depends factors such as (Sharholy et al, 2008):

• Food habits• Standard of living• Degree of commercial activities • Seasonal variation

MSW ManagementMunicipal Solid Waste

Refuse Trash

Routinecollection

Aperiodiccollection

Waste ProcessingEnergy Recovery

Recycling

Final Disposal

Energy Savings Of Recycling

Material Relative energy needed to manufacture versus energy generated from EfW incineration

Newspaper 2.6 times

Office paper 4.3 times

Glass containers 30 times

Tin cans 30 times

Aluminum cans 350 times

Plastics 3 – 5 times

Textiles 5 – 8 times

Comparison of MSW in 7 OECD and Asian countrieshttp://maps.grida.no/go/graphic/municipal_solid_waste_composition_for_7_oecd_countri

es_and_7_asian_cities

Comparison of MSW in 7 OECD and Asian countrieshttp://maps.grida.no/go/graphic/municipal_solid_waste_composition_for_7_oecd_countri

es_and_7_asian_cities

Comparison of MSW in 7 OECD and Asian countrieshttp://maps.grida.no/go/graphic/municipal_solid_waste_composition_for_7_oecd_countri

es_and_7_asian_cities

Collection of MSW

• Collection costs account for around 70 – 85% of the total solid waste management costs.

• There are three basic methods for waste collection:– Curbside collection– Set-out, set-back collection– Backyard pickup or total barrel method

• Curbside collection is considered the quickest and most economical method.

Transfer Stations• A transfer station is a facility at which solid

wastes from individual collection trucks are consolidated into larger vehicles.

• Individual transfer station capacities may vary from less than 100 tons to more than 500 tons of waste per day.

• Two basic modes of operation: direct discharge and storage discharge

Waste Hierarchy

Methods for Waste Management• Wealth from waste (processing of organic waste)

(A) Waste to compost

(i) Aerobic/ anaerobic composting

(ii) Vermicomposting

(B) Waste to energy

(i) Refuse derived fuel (RDF)/ pelletization

(ii) Bio-methanation

(C) Reuse of waste

• Sanitary landfilling

Waste processing methods

Biological processes

Composting

Anaerobic digestion

Compost

Biogas and digestate

Gasification/ Pyrolysis

Thermal processes

Incineration Heat, gaseous emissions and ash

Producer gas, solid fuel and tar

Major outputs

Major treatment processes for MSW and end products

Biological Processes• Composting

Composting is a process in which the organic fraction of MSW is decomposed by microbes under controlled aerobic conditions.

As a result, a stabilized product (also called compost) is produced that can be used as soil cover at landfills or conditioner.

Using composting process, the volume of the solid waste can be reduced by around 50%.

Composting process can be done in two ways: Windrow and in-vessel.

Windrow Composting In-vessel Composting

Compost produced

Biological Processes…..• Composting…..

Sometimes, sewage sludge or agricultural residues are also added with MSW. This is called ‘co-composting’.

Composting can also have negative impacts:Water pollution may exist if moisture content is very high (> 65%)Odor is another major problem from composting sites using open windrow method.

Home Composting

Which wastes? Non-woody yardwastes are the most appropriate.

Holding Units Turning Units

Which wastes? Non-woody yard wastes are appropriate. Kitchen wastes without meat, bones or fatty foods can be added to the center of a pile if it is turned weekly and reaches high temperatures.

Vermicomposting• Vermicomposting is a method of preparing compost

with the help of earthworm.

• Vermicomposting is a simple biotechnological process of composting, in which certain species of earthworms are used to enhance the process of waste conversion and produce a better end product.

• The process is faster in comparison to conventional composting.

Advantages of Vermicomposting• Productive utilization of organic wastes

materials such as agricultural wastes, animal dropping, forest litter and agro based industrial wastes for production of vermicompost.

• Vermicompost improve the physical, chemical and biological properties of the soil and crop productivity.

• Earthworms effectively harness the beneficial soil micro flora and destroy soil pathogen.

Precautions

• Maintain the moisture at 50-60 % level in the pit.

• Temperature remains between 25 – 28 ºC.

• Base material (Farm yard manure) should be partially decomposed.

• Proper aeration should be provided without disturbing the worms.

Biological Processes…..• Anaerobic digestion (Biomethanation)

If the organic waste is buried in pits under anaerobic conditions, it will be decomposed by anaerobic bacteria.

Thermophilic digestion is much faster and leads to the energy recovery through biogas generation.

Biogas contains 55 – 60% CH4 and 35 – 40% CO2.

There is a little experience in treatment of solid organic waste in India.

Thermal Treatment Processes• Incineration

It is a thermal process in which combustible portion of MSW is oxidized at high temperatures of around 1000°C.

Incineration can reduce municipal refuse by about 80 - 90% volume.

The major residue formed after the process include (bottom and fly ash) that may contain heavy metals.

In addition, gaseous emissions like CO2, NOx, dioxins etc. are also of major concern.

Pre-treatment Methods• Shredding and pulverizing

– Used for size reduction of waste components– Shredding refers to the actions of cutting and tearing– Pulverizing refers to the actions of crushing and grinding– Hammer mills is the most common type of equipment used

for processing MSW into a uniform or homogeneous mass.

• Baling– Compacting solid waste into the form of rectangular blocks or

bales is called baling.– MSW bales are typically 1.5 m3 in size and weigh roughly 1

kN.– Bales are produced by compacting the solid waste under high

pressures (~ 0.7 MPa)– Solid waste compaction ratio can be expressed in terms of

compaction ratio.Compaction ratio = initial volume/ final volume

Computation of Percent Volume Reduction After Compaction

• The initial volume of a mass of solid waste is 15 m3. After compaction, the volume is reduced to 3 m3. Compute the percent volume reduction and the compaction ratio.

Solution:Percent volume reduction = (15 – 3)*100/15= 80%Compaction ratio = 15/3 = 5

Landfilling

• This is the oldest and most widely used method for waste disposal.

• Land disposal may be done in two ways:

Open dumpingSanitary landfilling

Landfilling……• Sanitary landfilling has three key

characteristics:Waste is placed in an organized manner.

Waste material is spread and compacted.The waste is covered each day with a layer of compacted soil.

Provisions for capturing the landfill gas (CH4 and CO2 – two major constituents) are made.

Proper leachate (wastewater generated from a landfill site) collection system is also present.

Estimation of Landfill Area

• Estimate how many hectares of land would be required for a sanitary landfill, under the following conditions:

Design life of the site = 30 yearsMSW generation rate = 25 N/person/dayMSW compacted unit weight = 5 kN/m3

Average fill depth = 10 mCommunity population = 50,000MSW to cover ratio = 4:1 (20% of volume for cover)

SolutionThe quantity of MSW generated

per year = 25 x 50000 x 365 = 4.56 x 105 kN/yr

The volume of compacted refuse = 4.56 x 105/ 5 = 91250 m3/yr

The additional volume for soil cover = 91250/4 = 22813 m3/yr

Total required volume = 91250 + 22813 = 114063 m3/yr

The area required = volume/depth= 114063/10 = 11406 m2/yr

Total landfill area required= 11406 x (30 yrs)/ 104 ha= 34 ha