Wastewater Treatment TechnologiesSumona Mukherjee

PhD Student

Introduction

It is unhealthy for humans, pets, and wildlife to drink or come in contact with surface or ground water contaminated with wastewater.

Inadequate treatment of wastewater allows bacteria, viruses, and other disease-causing pathogens to enter groundwater and surface water.

Hepatitis, dysentery, and other diseases may result from bacteria and viruses in drinking water.

Disease-causing organisms may make lakes or streams unsafe for recreation. Flies and mosquitoes that are attracted to and breed in wet areas where wastewater reaches the surface may also spread disease.

Wastewater is the combination of liquid and water-transported wastes from homes, commercial buildings, industrial facilities, and institutions, along with any groundwater infiltration and surface water and stormwater inflow that may enter the sewer system.

Point sources of wastewater are discrete and identifiable sources that are divided into domestic and industrial sources. Domestic sources include residences and small businesses. Compared with industry, these are relatively small sources. As a result, a major issue in this category is the collection of wastewater (i.e., it is a major expense when added up for the entire community)Industrial sources are relatively large sources that include such sub-categories as the chemical, pharmaceutical, oil, mining, and metal industries. Because of their size, these sources are generally easier to collect, but harder to treat (e.g., their chemical content can vary tremendously).

Introduction

Source of Wastewater

Source of Wastewater

Non-point sources are diffuse and generally occur from water runoff. Because they are spread over large areas, they tend to be more difficult to control, and in recent years they have gained greater attention from legislators. They are divided into agricultural, urban, and atmospheric sources.  

Agricultural sources include farms, which can contribute fertilizers, pesticides, soil erosion, and plant and animal wastes to water runoff. Collectively, they usually constitute the largest source of pollutants to water, and the erosion contributions are being worsened by the deforestation occurring in various parts of the world.  

Urban sources include the storm water systems that collect water from the gutters of streets in towns and cities. The true scope of the problem from urban sources is still not very well understood, but it is clearly a major contributor.  

Atmospheric sources include air pollution's contribution during precipitation (e.g., acid rain). We do not discuss it in detail here because we have already covered it in a previous section. Nevertheless, it is a classic example of the multi-media role of wastewater pollution.

Selection of wastewater treatment options

The selection and design of treatment facilities is based on a study of

• the physical, chemical and biological characteristicsof the wastewater• the quality that must be maintained in theenvironment to which the wastewater is to bedischarged or for the reuse of the wastewater• the applicable environmental standards or dischargerequirements that must be met

Characteristics of wastewater

Contaminants of concern in wastewater treatment

Contaminants Reason for concern

Suspended solids Sludge deposits and anaerobic conditions

Biodegradable organics

Depletion of natural oxygen resources and the development of septic conditions

Dissolved organics Inorganic conditions added by usage.Reclamation and reuse application.

Heavy metals Metallic constituents added by usage.Many metals are also classified as priority pollutants

Nutrients Growth of undesirable aquatic life; eutrophications

Pathogens Communicable

Priority organic pollutnts

Suspected carcinogenicity, mutagenicity, teratogenicity, or high acute toxocity.Many priority pollutants resists conventional treatment methods (known as refractory organics)

Organic WasteCOHNS

End Products

New Cell Tissue C5H7NO2

Oxidation

Synthesis

energy

energy

O2

Stable organic end product

O2

O2

Endogenous respiration

Schematic diagram of the aerobic biological conversion of organic matter in wastewater to end products, to new cells and ultimately to stable organic and other end products

A:B:(to be written)

Typical composition of untreated domestic wastewater

Unit waste loading factors

Minimum national standards for secondary treatment

Typical flow diagram for the treatment of domestic wastewater

Levels of wastewater treatment

Application of physical unit operations of wastewater treatment

Circular comminutor

Removal of Grit

Typical examples of grit chambers (a) Aerated grit chamber (b) Vortex type

Screening Devices used for the removal of solids

Devices used for mixing of chemicals in wastewater

Devices used for transfer of oxygen into the wastewater

Devices used for sedimentation of wastewater

Devices used for sedimentation of wastewater

Typical horizontal-lamp parallel-flow ultraviolet (UV) facility used for the inactivation of microorganisms

Applications of Chemical unit process in wastewater treatment

Major biological treatment processes used for the wastewater treatment

Typical design parameters used the activated sludge processes

Typical design parameters used the activated sludge processes

Trickling Filters

Typical design parameters for various types of trickling filters

Rotating Biological Contractor

Typical design parameters for the various types of trickling filters

Pond system for the treatment of wastewater

Land application of wastewater

Typical flow diagrams for the removal of nutrients from wastewater

Filtration system for wastewater reclamation system

Sludge processing methods

Sludge processing methods

Typical two stage sludge digestion facility

Advanced treatment processes used to purify treated water

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