Solid Waste Final Exam

What is bioremediation?

The use of microorganisms to control and destroy contaminants

What is ex-situ treatment?

Excavating contaminated material and treating it

Typical pump and treat trend

High initial decrease in contaminant concentrations, then slower decrease over time

Soil vapor extraction

In situ volatile organic treatment in unsaturated zone

Air sparging

In situ volatile organic treatment in saturated zone

What makes hazardous waste treatment difficult?

Contaminants have wide variety of media and source strength

Two basic questions that must be answered after investigating a site and defining the associated hazards

1. To what level should the site be remediated to protect human health and the environment?
2. How should this level of protection be achieved?

Three factors used rank technologies in FS

Effectiveness, implementability, cost

Five general types of remedial technologies

1. Containment
2. Extraction
3. Treatment
4. Disposal
5. No action

What is risk?

Probability of suffering harm or loss

Source zone

Where the bulk of the contaminant mass is usually found

One example of a contaminant source that is extremely difficult to locate and remove

NAPLs

NAPL - define + example

Non-aqueous phase liquid
Oil

DNAPL - define + example

Dense non-aqueous phase liquid
Chlorinated Solvent

LNAPL - define + example

Light non-aqueous phase liquid
Crude oil + petroleum products

Advection

A solute that moves with the flow of groundwater

Conservative solute

Nonreactive chemicals dissolved in groundwater

Solute

Chemicals dissolved in groundwater

Hydraulic conductivity

The ability of porous media to transmit water

Hydraulic gradient

Gravity and pressure driving groundwater movement

Adsorption vs absorption

ADsorption - solute accumulation is restricted to a surface or the interface between solution and adsorbent
ABsorption - solute interpenetrates the sorbent

Dispersion- define + mechanism

Plume mixing with surrounding water as it moves

What is site characterization?

The qualitative and quantitative descriptions of the conditions on and beneath the site

How does site characterization fit into Superfund?

It is phase 1 of the remedial investigation

Soil resistivity testing

Resistance to current flow as a result to applied electrical potential

Seismic surveys

Creating a seismic wave to find the depth to bedrock and information on overburden

Ground-penetrating radar

Radio waves penetrating the soil to find buried materials

Soil-gas surveys

Indirect method for detection and mapping of subsurface hydrocarbon contamination

Key drilling methods

• Solid stem auger
• Hollow stem auger
• Rotary drilling

Two uses of monitoring wells

Measuring hydraulic head and sampling groundwater

2 responses that EPA uses to clean up sites

Removal - emergency spills
Remediation - long term

NPL

National priority list - eligible sites for cleanup under Superfund

Hazard ranking system

Screens and identifies sites eligible for NPL

Three categories of factors in the hazard ranking system

1. Likelihood of release
2. Waste characteristics
3. Targets

Four pathways in the hazard ranking system

1. Groundwater
2. Surface water
3. Soil
4. Air

Cut-off score for inclusion on the NPL

Root-mean square > 28.5

Potentially responsible parties

The polluter: owners, former owners, operators, waste generators, and/or transporters

Three steps involved in the anaerobic microbial conversion of organic compounds in landfills

1. Hydrolysis/Fermentation
2. Acidogenesis
3. Methanogenesis

Principal gases formed under aerobic and anerobic conditions

CO2, CH4, NH3, H2S

2 means for controlling gas movement

1. Vented into the atmosphere
2. Collected for energy

Leachate

Liquid that has percolated through solid waste and has extracted solutes

Importance of controlling surface water infiltration

More water that enters a landfill = more contaminated water exiting a landfill

2 primary types of liners

Clay liners, composite liners

State the two approaches for leachate collection

Sloped terraces or piped bottom

Sanitary landfill

An engineered facility used for disposing of solid wastes on/in land without creating hazards

What MSW goes in sanitary landfills?

Landfills are regulated under

RCRA, Subtitle D

Evaluating a solid waste disposal site

Geologic and hydrologic conditions + social factors

Lift and cell

Lift: complete layer of cells over the active area of the landfill
Cell: waste deposited in each operating period

3 principal landfilling methods

1. area method
2. excavated cell/trench
3. canyon/depression

Landfill classifications

I: Hazardous Waste
II: MSW
III: Construction, demolition, and non hazardous industrial wastes

Landfill location restrictions

Airports, floodplains, wetlands, fault areas, seismic impact zones, unstable areas

Combustion

Rapid chemical reaction of oxygen and fuel

Benefits of combustion in MSW

1. MSW volume can be significantly decreased
2. Energy can be recovered

5 principal categories of issues associated with the use of combustion facilities for transformation of MSW

Siting, air emissions, residual disposal, liquid emissions, and economics

Principle elements of solid waste

C, H, O, N, S

Composting

Organic material that is broken down by microbes

Composting objectives

1. Create biologically stable material
2. Reduce volume of waste
3. Destroy pathogens
4. Retain nutrients
5. Produce product that can be used on soil

3 steps in composting operations

1. pre-processing waste: receiving, sorting, size reduction
2. processing: decomposition of organics
3. Preparation and marketing of final product

Ideal composting moisture content

50-60% by weight

Ideal composting C:N ratio

25-30:1 - preferred
20-40:1 - reasonable

3 techniques of composting

1. Windrow
2. Aerated Static Pile
3. In vessel System

Two basic options for separation of waste materials

Separation at the source
Separation at Material Recovery Facilities (MRFs)

Objective of mechanical size reduction

To get a product that is uniform and reduced in size

3 primary types of shredding equipment used for the processing of wastes

Hammer mill, flail mill, shear shredders

Objective of screening

Separate mixtures of materials into different sizes

3 primary types of screening equipment used for processing of wastes

Rotary screens, vibrating screens, disc screens

Air classification

Separating light materials from heavier ones

2 major types of magnetic separation equipment

Magnetic head pulley, magnetic belt pulley

Aluminum separation process

Eddy current separator

Objective of densification

Increase density of waste materials to be stored more efficiently

2 types of equipment used for densification

Balers and can crushers

5 Recycling steps

1.diversion, storage, collection
2. processing and preparation
3. Sale or donation
4. Manufacturing of new products
5. Purchasing product

2 benefits of recycling

Conversion of natural resources
Conversion of landfill space

Recycling issues

1. Correct materials have to be diverted
2. Need strong demand for reuse and recycling
3. Needs to be cheaper than raw materials to sell

3 major factors (profits and costs) to consider when evaluating the economics of recycling

1. Value of recycled material
2. Avoided costs
3. Recycling cost

3 factors that led to recycling becoming an important part of ISWM in the late 20th century

1. belief that recycling is good for the environment
2. desire for solid waste management other than landfills
3. Legislative and regulatory actions

4 key chemical properties of MSW to be used as a fuel

1. moisture
2. volatile combustible matter
3. fixed carbon
4. ash

Major categories of sources of solid wastes

Domestic residences, commercial and institutional, industrial and agricultural, municipal services waste

MSW

Municipal Solid Waste - all community wastes except industrial process wastes and agricultural wastes

Total per capita "refuse" generation for 2018

4.9 lb/capita/day

Total per capita MSW generation for 2018

6.1 lb/capita/day

2 broad categories of legislation related to hazardous wastes that were initially enacted

Management and remediation

2 primary goals of RCRA

1. Protect public health and the environment
2. Preserve natural resources

Primary purpose of CERCLA

Remediate hazardous waste sites

3 generator categories

1. Small quantity generator
2. Large quantity generator
3. Conditionally exempt

4 Rs

Reduce, reuse, recycle, recovery

Type 1, 2, & 3 industrial ecosystem

1: Material is extracted, used, then discarded
2: Material is extracted, used, then recycled or discarded
3: Closed loop, sustainable use of resources

Industrial symbiosis

Moving type 1/2 industrial ecosystems to a closed loop type 3 industrial ecosystem

Integrated Solid Waste Management Ranking (4)

1. Source reduction and reuse
2. Recycling/composting
3. Energy recovery
4. Landfill

Ecosystem

A community of organisms interacting with each other and their environment