Skip to main content
Printable page generated Saturday, 24 February 2024, 1:41 AM
Use 'Print preview' to check the number of pages and printer settings.
Print functionality varies between browsers.
Unless otherwise stated, copyright © 2024 The Open University, all rights reserved.
Printable page generated Saturday, 24 February 2024, 1:41 AM

Hygiene and Environmental Health Module: 18.  Introduction to the Principles and Concepts of Waste Management

Study Session 18  Introduction to the Principles and Concepts of Waste Management


In this study session you will learn about the basic concepts and principles of waste management. The definition of common terms and discussion of the concepts, principles and classification of wastes will help you understand the subject of waste management. You will also learn about the public health importance of solid waste and liquid waste management, and be introduced to the basic principles and process of waste decomposition. This is relevant for you to understand how waste is decomposed and can be treated or made safe from pathogenic organisms.

Learning Outcomes for Study Session 18

When you have studied this session, you should be able to:

18.1  Define and use correctly all of the key words printed in bold. (SAQ 18.1)

18.2  Outline the basic concepts and principles in waste management. (SAQs 18.2 and 18.3)

18.3  Describe the public health importance of solid and liquid waste management. (SAQ 18.4)

18.4  Identify the main types of waste and their sources. (SAQ 18.5)

18.1  Basic principles and concepts of waste management

Waste is introduced into the environment due to the day-to-day activities of humans. Waste management refers to the many methods and processes of dealing with waste at every stage from generation and collection through to final disposal.

Waste needs to be managed in order to prevent contact with humans or their immediate environment. Therefore, the main purpose of waste management is to isolate waste from humans and the environment, and consequently, safeguard individual, family and community health. In addition, the aesthetic value of a better outlook and a clean physical environment is important for our emotional wellbeing.

The waste we produce can be categorised as liquid waste or solid waste depending on its physical state. It can also be categorised as hazardous or non-hazardous (see Box 18.1).

Box 18.1  Hazardous and non-hazardous waste

Hazardous wastes are not classified by their physical state (solid, liquid or gas) but by their properties and potential to cause harm. Hazardous wastes are defined as wastes that have one or more of the following properties. They may be:

  • corrosive (substances that cause damage on contact, e.g. acids)
  • ignitable (materials that can catch fire easily like benzene)
  • toxic (materials that can be poisonous to humans when inhaled or ingested, or come in contact with skin or mucous membranes)
  • reactive (substances that can yield a harmful chemical if they react with other substances)
  • infectious (substances that are capable of causing or communicating infection).

Potential sources of hazardous waste in rural households include obsolete pesticides, herbicides or rodenticides.

Non-hazardous wastes include all other types of waste.

18.1.1  Liquid waste

Liquid waste includes human waste, runoff (storm water or flood water), sullage, industrial wastewater and other forms of wastewater from different sources. Human waste is mainly composed of faeces and urine, which together are known as excreta. All human body waste is classed as liquid waste. The mixture of human waste with wastewater is known as sewage and also sometimes known as blackwater. Runoff is simply rainwater that collects on the ground and runs off into channels, ditches and rivers. Sullage, also known as greywater, is water that has been used for washing in bathrooms and kitchens; it does not include human waste.

Human waste is biodegradable (see Box 18.2) and when contained in a waste containment facility (for example, a pit latrine or septic tank) it undergoes a biological digestion process by which microorganisms, particularly bacteria, decompose the organic matter. The decomposing bacteria found in pit latrines and septic tanks do not require oxygen and are called anaerobic bacteria. The digestion process may take from several days to a few months, depending on the atmospheric temperature and other local conditions, before it is completely decomposed or degraded. The digested waste matter is called sludge.

Box 18.2  Biodegradable and non-biodegradable wastes

Biodegradable wastes are those that can be broken down (decomposed) into their constituent elements by bacteria and other microorganisms. The term can be applied to both liquid and solid waste. Human and animal wastes, food waste, paper, and agricultural wastes are all biodegradable. This natural biological decomposition process ensures that, under the right conditions, these wastes do not accumulate in the environment.

Many plastics are not biodegradable and these create environmental problems because they remain unchanged for many years (Figure 18.1). The bacteria responsible for biodegradation may be aerobic, meaning they require oxygen, or anaerobic, meaning they do not need oxygen to survive. Decomposition of biodegradable wastes by anaerobic bacteria is sometimes called digestion.

Non-biodegradable plastics
Figure 18.1  Non-biodegradable plastics are a problem because they persist in the environment and do not decompose. (Photo: Pam Furniss)
  • Do you think human waste is a danger to health?

  • Yes it is. Human waste must be considered as potentially infectious matter because it may contain pathogenic organisms.

Although human waste is a potential source of disease, the amount of human faeces disposed of indiscriminately in open fields and under bushes, mostly in rural settings of Ethiopia, is a major problem. In rural areas, a large proportion of households do not have pit latrines and although this situation is changing, open defecation continues to be widely practised. Open defecation can spread disease, contaminate the soil and pollute drinking water sources, as discussed in previous study sessions. To avert these risks, households and communities should work towards community goals to be ‘open defecation free’. This can be achieved through the building, and consistent use of, onsite communal or human waste disposal facilities. You will learn more about this in later sessions of this Module. Onsite facilities are, for example, pit latrines built in the compound of households; communal or public facilities are latrines built in streets or in market places. These public latrines are also referred to as municipal facilities.

18.1.2  Solid waste

Solid waste is defined as any waste that is dry in form and is discarded by people as unwanted. You can describe the solid waste from general housekeeping as residential waste, refuse, household waste or domestic waste. Waste produced in other areas is defined as industrial, commercial, institutional or agricultural waste, or street sweepings, depending on its source. In urban settings, municipal waste refers to the solid waste that is collected by local government (the municipality) and may include household, commercial, industrial waste and street sweepings. The solid waste that is produced as a result of food preparation, or any foodstuff leftover after eating, is called kitchen waste or garbage.

Understanding the appropriate methods for the management of solid waste is closely related to the characteristics of the waste and therefore to its source. Considering the sources one by one:

  • a.Residential waste or domestic waste is generated from households. It is mostly characterised as non-hazardous wastes, especially in rural households. It may include rubbish, such as packaging materials, kitchen wastes, ash, etc.
  • b.Agricultural solid wastes could include food residues, animal dung, crop residues, grass and leaves. Such wastes are mostly non-hazardous and biodegradable in nature. However, containers for used or obsolete pesticides, herbicides and rodenticides could be a health hazard to families and sprayers. Therefore, these items should be safely removed in collaboration with the agricultural development extension agents in your kebele.
  • c.Commercial wastes are those generated from business establishments, food and drink service establishments, shops, or open market places. These vary a great deal but may include packaging paper, cardboard, electronics, timber, wire, metals, plastic bags (festal), tin cans, garbage and other wastes that are generally of non-hazardous nature.
  • d.Industrial waste can be produced from small, medium or large-scale industries. The type of waste produced may vary depending on the raw material used and the product of the industrial process. These wastes may be hazardous or non-hazardous, depending on the process. The solid waste produced could contain chemicals, wood, metal, ceramic or other components.
  • e.Institutional solid waste is produced from public or government institutions, offices, schools, universities, religious institutions, sporting fields, etc. It can be very mixed in its components.
  • f.Healthcare waste is produced from healthcare facilities such as Health Posts, health centres and hospitals. This category of waste is composed of both hazardous (infectious) and non-hazardous wastes (also referred to as general waste). The management of healthcare waste needs special attention and is discussed in Study Session 23.

The rate of production and characteristics of residential or domestic solid waste depends on cultural habits, urbanisation, season of the year and the agro-ecological zone of the area.

  • Can you think of some differences in the kitchen waste produced in the dry and wet seasons?

  • Your answer will depend on where you live and the type of foodstuff that is ripe during that particular season but you may have answered leaves of maize and maize husk, peelings of potatoes or sweet potatoes during the wet seasons and pods of chick peas (shimbra tirtir) during the dry season.

Urban and affluent societies tend to produce greater quantities of solid waste than rural communities. Rural waste comes from households and agricultural activities and is mostly organic and biodegradable in nature. This makes it suitable for making compost. Compost is a mixture of decomposed organic matter, mostly of plant origin, that can be used to improve soil structure and to return nutrients to the land.

Solid waste generated from households in your community will consist mostly of organic decomposable matter that will be broken down through bacterial action. In urban areas, where there is a large amount of solid waste, it is usually taken to a landfill site for disposal. Landfill sites, also known as dumps or rubbish dump sites, are sometimes located in places such as former quarries where the waste can be used to fill in a hole in the ground, hence the name ‘land fill’. In landfill sites and some community waste disposal sites, the solid waste decomposition process will produce leachate. Leachate is formed when the liquid fraction from a mixed solid waste is separated by gravity from the solid component. Unless controlled, the leachate will seep out from the bottom of the waste tip and can pollute surface and groundwater. It may contain toxic chemicals in addition to pathogenic microorganisms. The biosolids (the solid fraction) as well as the leachate formed in this process need to be disposed of safely in a way that will not affect the environment or human living conditions.

18.2  Public health importance of waste management

How does waste management affect public health and the environment? Improper disposal of wastes, such as solid waste, human excreta and sewage, is one of the major risk factors that affect the health and comfort of individuals in rural Ethiopia where municipal or onsite facilities do not exist, or are not functional.

  • Name three diseases or pathogens that are transmitted in human waste.

  • There are many possible answers. You could have said diarrhoea, trachoma, amoebic dysentery, giardiasis, rotavirus, cholera, salmonellosis, shigellosis and other diarrhoeal diseases. In addition, you may have mentioned hookworm, roundworm, whipworm, tapeworms, schistosomiasis, filariasis, leptospirosis and many more. A very long list!

Poor waste handling and disposal can lead to environmental pollution, encourage the breeding of disease-vector insects, animal scavengers and rodents, and result in a range of diseases through different routes of exposure such as faeco-oral and soil transmitted mechanisms.

Figure 18.2 shows these routes of exposure diagrammatically; you may remember this diagram from Study Session 1. In this figure, you can see that faeces are the common source of contamination to the other ‘Fs’ – fluids, fingers, fomites and flies. These then contaminate our food and, consequently, a new susceptible human host.

The ‘F-diagram’
Figure 18.2  The ‘F-diagram’ showing the faeco-oral disease transmission pathways.

Survey studies conducted in different parts of Ethiopia indicate that there are many highly prevalent faeco-orally transmitted intestinal parasites and other infectious agents (bacteria and viruses) in our environment. To break the transmission route of these disease agents, there needs to be total sanitation, which means prevention of any human contact with waste, i.e. no open defecation and the proper handling of solid waste. The broken lines in Figure 18.2 show the points at which a barrier or intervention can be made to prevent transmission. The first line of defence is to contain the faeces. The second is to protect the food from contamination and the third is to protect the potential host, the person who may become infected, from contaminated food, fingers, drinking water or other objects. To achieve total sanitation, the community needs to be involved in any plan to clean the local environment and must initiate its own waste disposal methods. You will learn some of the techniques that are used to encourage this sort of behavioural change in Study Session 21.

In addition to the dangers of disease transmission, health hazards associated with improper solid or liquid waste disposal include:

  • Public or community nuisance due to foul odour and unsightliness of open defecation faecal matter and openly dumped solid wastes.
  • Obstruction of drainage systems leading to creation of favourable conditions for disease vector breeding sites.
  • Fire hazards.
  • Psychological health hazards.

18.3  Main components of waste management

In any waste management process, there is a stage when waste will be temporarily stored or contained onsite (i.e. in the place where the waste is produced). This may be temporary or be a final disposal site. If storage is temporary, then subsequent stages will be the transfer or transport to a treatment facility or technology, followed by final disposal offsite (i.e. away from the waste generation site).

18.3.1  Liquid waste management

Liquid waste management will include both onsite sanitation and offsite treatment and disposal methods. The most usual method of onsite liquid waste containment in rural Ethiopia is the pit latrine. Pit latrines are simple drop-and-store systems in which the liquid waste collects in a pit below. There are many different designs of pit latrine (Figure 18.3 and Figure 18.4), which are described in more detail in Study Session 20.

A traditional pit latrine
Ventilated improved pit latrine.
Figure 18.3  A traditional pit latrine. (Photo: Worku Tefera)Figure 18.4  Ventilated improved pit (VIP) latrine. (Note the vent pipe emerging through the roof). (Photo: Worku Tefera)

In places where water is more easily available, typical methods are drop-flush-and-discharge systems, also known as water carriage systems, such as the pour-flush latrine (Figure 18.5) or a water closet (WC) (Figure 18.6).

Pour-flush latrine
Water closet toilet
Figure 18.5  Pour-flush latrine. (Photo: Eawag)Figure 18.6  Water closet (WC) toilet. (Photo: Worku Tefera)

Wastewater from water carriage systems may be piped into a septic tank or into a community or municipal treatment system, if one exists. The various types of latrine and methods of liquid waste management are discussed in more detail in Study Sessions 19 and 20.

18.3.2  Solid waste management

Solid waste management can be classified into five main stages. These stages are also referred to as the functional elements of solid waste management. These are:

  • onsite handling, storage and processing
  • collection
  • transfer and transport
  • resource recovery and processing
  • disposal.

Onsite handling, storage and processing methods are undertaken at household level. This includes compacting waste by squashing it and changing its size and shape for easy handling. It also includes sorting the waste in order to separate the items that can be reused or recycled. For example, organic wastes should be separated out for composting as part of onsite handling. Bottles and cans can be reused. Collection and transfer or transport activities are not common in rural areas because the waste is usually disposed of immediately onsite in a prepared waste disposal or composting pit. (The five functional elements of solid waste management are discussed in more detail in Study Session 22.)

Ideally, waste management should go beyond pollution prevention and disease prevention for humans and should benefit society by providing economic gain for families and communities. The preferred approach for dealing with solid waste is integrated solid waste management (ISWM). ISWM means considering not only the appropriate disposal of solid waste but integrating this with other management options such as minimising waste production, recycling, composting and other waste recovery options. The advantages of ISWM are that it considers all options and aims to manage waste in ways that are most effective in protecting human health and the environment. ISWM can also have many economic and social benefits for your community. For example, you could consider composting of human waste and animal manure to produce natural fertiliser for gardening and for cultivating vegetables and crops. Some solid wastes can be recycled or reused. You could also consider helping your community in the development of a biomass waste digestion plant that will produce biogas to be used for cooking and lighting energy. Biomass is any biological material from living or recently living plants that is used to generate energy, usually in the form of biogas.

18.4  Compare the different waste management methods

There are a range of sanitation technologies currently in practice that you may want to recommend to institutions, communities and households in your area. ‘Sanitation technologies’ is a general term used to describe any kind of waste treatment and disposal. It can refer to specific infrastructure, methods or services that are designed to contain, transform or transport waste. It therefore includes the facility used by the person, such as pit latrines, WCs, etc. and also the storage/treatment processes such as septic tanks, biogas reactors etc. The effectiveness and efficiency of waste management facilities varies greatly because of the advantages and disadvantages each one of them has in terms of capacity to remove pathogenic organisms, cost of the technology, acceptability of the sanitation technology by the end users such as families and individuals, and the skill level needed for proper operation and maintenance of the scheme. If you have a good understanding of the different sanitation technologies then you will be able to identify those that are appropriate for your community. An appropriate sanitation technology is one that is economically affordable, socially acceptable and environmentally sustainable. You will then be in a good position to offer advice to household heads, community leaders, kebele leaders, sectoral government officers, local institutions such as schools and private firms about their choice of technology.

In later sessions we will discuss the advantages and disadvantages of different solid and liquid waste disposal methods that can be used at communal and individual household level so that you can apply your knowledge to your local situation.

Summary of Study Session 18

In Study Session 18, you have learned that:

  1. Waste can be categorised as solid or liquid waste based on its physical state. It can also be categorised as hazardous and non-hazardous waste.
  2. Liquid waste includes human waste, runoff (flooding), sullage (or greywater) and other forms of wastewater from different sources.
  3. Solid waste is any dry waste that is discarded by people because they no longer need it. It can arise from households, industrial, commercial or agricultural activities, or from streets.
  4. Human waste is biodegradable, meaning it will decompose by a biological process due to microorganisms, particularly bacteria.
  5. The type, generation rate and characteristics of solid waste depend on the source of the waste and on cultural habits, urbanisation, season of the year and the agro-ecological zone of the area.
  6. Poor waste management could result in various diseases, accidental fire or nuisance conditions for the environment and families.
  7. Properly managed waste could benefit your community socially and economically by recycling and reusing waste, where possible.
  8. The main components of solid waste management include onsite handling, storage and processing; waste collection; transfer and transport of solid waste; and waste recovery and final disposal.

Self-Assessment Questions (SAQs) for Study Session 18

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the Notes on the Self-Assessment Questions at the end of this Module.

SAQ 18.1 (tests Learning Outcome 18.1)

The Glossary Game: Write down each of the key words printed in bold in this study session. Cut the paper into strips, with one word on each strip; fold them and put them into a bowl. Take a strip, read the word and write a definition in your Study Diary. Then check your definition with those in the study session.


This game is intended to familiarise you with the technical terms you will meet again in subsequent study sessions. To find the right answer, you can check the definition written in your own words with that in the study session.

SAQ 18.2 (tests Learning Outcome 18.2)

Waste can be categorised as solid or liquid, and as hazardous or non-hazardous. Give an example of a:

  1. solid non-hazardous waste
  2. liquid non-hazardous waste
  3. solid hazardous waste
  4. liquid hazardous waste.

You may have come up with different suggestions but we thought of these examples:

  • vegetable peelings and waste from food preparation
  • water that has been used to wash clothes
  • used dressings and bandages from the Health Post
  • diesel fuel leaking from a damaged can.

SAQ 18.3 (tests Learning Outcome 18.2)

What is the main purpose of waste management?


The main purpose of waste management is to isolate waste from humans and the environment, and protect human health.

SAQ 18.4 (tests Learning Outcome 18.3)

Outline three benefits for public health that can be provided by proper waste management.


There are many public health benefits including prevention of faeco-orally transmitted diseases, reduction in public nuisance from wastes in the environment, creation of a more aesthetically pleasant environment, and the possibilities of generating income from creating economically valuable products from the treatment, recycling and reuse of waste.

SAQ 18.5 (tests Learning Outcome 18.4)

Match the sources of waste with the types of solid waste below.

Using the following two lists, match each numbered item with the correct letter.

  1. Manures

  2. Packaging materials, plastics

  3. Needles and other sharps

  4. Coffee bean shells

  • a.Coffee processing

  • b.Agricultural

  • c.Healthcare

  • d.Commercial

The correct answers are:
  • 1 = b
  • 2 = d
  • 3 = c
  • 4 = a