Study Session 10 Disposal of Solid Wastes

Transcription

1 Study Session 10 Disposa of Soid Wastes Copyright 2016 The Open University

2 Contents Introduction 3 Learning Outcomes for Study Session Options for waste disposa Landfis Indiscriminate waste disposa Communa open dumping Buria in a pit Controed andfi Sanitary andfi Panning controed andfis for sma and medium-sized towns Estimation of the required and area Finding a suitabe ocation Therma processing methods Open burning Incineration Types of hazardous waste Househod hazardous waste Management of hazardous waste 15 Summary of Study Session Sef-Assessment Questions (SAQs) for Study Session of 19 Wednesday 30 March 2016

3 Introduction Introduction So far, in the series of study sessions focusing on soid waste management, you have studied sources and quantities of waste (Study Session 7), ways of reducing, re-using and recycing wastes (the 3 Rs ; Study Session 8), and ways of coecting the remaining waste (Study Session 9). Unfortunatey, after practising the 3 Rs, we are often sti eft with a portion of waste to be disposed of. In this study session you wi ook at the different disposa options and how they can be used in urban areas in Ethiopia. You wi aso earn more about hazardous waste and how it shoud be managed. Learning Outcomes for Study Session 10 When you have studied this session, you shoud be abe to: 10.1 Define correcty a of the key words printed in bod. (SAQs 10.1, 10.2, 10.3 and 10.5) 10.2 List the main options avaiabe for soid waste disposa and describe their advantages and disadvantages. (SAQs 10.1, 10.2 and 10.3) 10.3 Describe the key factors to consider when panning a andfi for a sma or mediumsized town. (SAQ 10.4) 10.4 Describe how toxic and other hazardous waste can be disposed of safey. (SAQ 10.5) 10.1 Options for waste disposa Waste disposa processes aim to isoate the waste from peope and the environment in a manner that causes no harm. The best option for deaing with any particuar waste depends on the nature of the waste itsef (its form, composition and quantity), the technoogies avaiabe in the region, the avaiabiity of financia resources, and having enough skied peope to buid, operate and maintain the faciities. In Ethiopia, two main waste disposa processes are widey used: andfi, incuding buria and dumping, and therma processing, which incudes burning and incineration. Different methods of andfi and therma processing are described in the foowing sections Landfis Landfi was defined in Study Session 1 as an area of and set aside for the fina disposa of soid waste. Ideay the site is managed to prevent peope and animas from entering and the deposited waste is covered with soi to isoate it from the environment. However many informa sites do not cover the waste or have any other contro measures. We are using andfi here as a genera term that appies to any site where soid waste is deposited for fina disposa. 3 of 19 Wednesday 30 March 2016

4 10.2 Landfis There are many different types of andfi, some with greater environmenta impact than others. In a of them the waste graduay decomposes by a combination of bioogica, chemica and physica processes. During these decomposition processes, two major emissions are of primary concern eachate and andfi gas: Leachate is the pouted water that emerges at the base of the andfied waste. It is formed in two ways. Rainwater anding on the waste sowy fows over and through the waste and soube substances are dissoved in the water. Aso, some of the decomposition reactions taking pace in the waste produce iquid that can be acidic. Some substances, such as toxic metas, tend to dissove more easiy in acids, making the fina eachate more harmfu. If eachate enters a watercourse used to provide human or anima drinking water or for irrigation, peope can be exposed to these poutants. Landfi gas is formed in arge andfis through degradation of the waste in anaerobic conditions. Landfi gas consists of a mixture of carbon dioxide and methane, which are both greenhouse gases that contribute to goba cimate change. It is aso fammabe and wi burn if exposed to a fame or other source of ignition. In extreme cases, the gas can buid up in a andfi and expode, with the risk of injury and death. Managed andfi sites have vent pipes that aow the gas to get out of the waste and be reeased to the air or burned in a controed way. The different types of andfi can be ranked according to their potentia to cause environmenta poution. Starting with the worst, they are: 1 Indiscriminate waste disposa 2 Communa open dumping 3 Buria in pits 4 Controed andfi 5 Sanitary andfi. These types of andfi are described in the foowing sections Indiscriminate waste disposa This is the most unwanted and dangerous practice in soid waste management. It occurs when an individua eaves waste by the roadside, on a piece of disused and, in a fied, by the side of a riverbank or in a river (Figure 10.1). This practice is very common in urban areas in Ethiopia and is aso known as open dumping. 4 of 19 Wednesday 30 March 2016

5 10.2 Landfis Figure 10.1 Open dumping on the banks of a river. Why do we discourage open dumping? Open dumping is discouraged for a number of reasons. It: attracts fies, rodents and birds fies contaminate our food, causing food-borne inesses rodents can transmit a range of diseases and can damage property birds disperse pathogens in their faeces is unsighty and causes bad odours aows waste, especiay paper and pastic bags, to be bown around by wind causes fire hazards 5 of 19 Wednesday 30 March 2016

6 10.2 Landfis is a hazard for grazing animas can bock rivers and drains, causing fooding Communa open dumping This method is practised in many sma and medium-sized towns in Ethiopia. A convenient area of and near the town is identified, frequenty in a vaey or a natura depression in the ground. Waste is then deposited at the site and graduay accumuates over time. At their worst, these sites have no barrier to keep out animas, there is no equipment to move or compact the waste, no environmenta contro measures, and no site staff. (Compacting means reducing the voume occupied by andfied waste by pressing down on it, usuay by driving over it with a tractor or other heavy vehice.) Open dumping can be an effective way of isoating waste from peope, but adverse effects can emerge in the ong run, such as: There is no barrier between the waste and the ground beow so eachate can contaminate groundwater and surface waters. The areas seected for such sites are often some distance from the community and not accessibe to carts and other wheeed transport. This means that the waste must be carried to the site, which is time-consuming. Some peope wi be tempted to dispose of waste indiscriminatey rather than wak a the way to the site. Uness the site is we ooked after (which is unikey), waste can be bown off the surface by the wind and the exposed waste may attract fies, rodents, dogs, hyenas and birds. Finay, if the waste is deposited in a normay dry vaey, fooding can occur in the event of unexpected heavy rain. The rainwater wi become contaminated with eachate and with waste items such as pastics Buria in a pit This is practised mainy in the yards of individua househods. It can be an effective way of deaing with waste, especiay when the waste is covered by earth every day. But care must be taken in choosing where to position the pit so that there is no danger of eachate contaminating groundwater or surface water. Another disadvantage is that these pits cannot accommodate a huge voume of soid waste, so a househod coud run out of disposa space. An exampe of a buria pit, which is fenced to keep out animas and chidren, is shown in Figure of 19 Wednesday 30 March 2016

7 10.2 Landfis Figure 10.2 Waste pit for a sma community Controed andfi For urban waste disposa, a controed andfi is a significant improvement on the communa open dump. The area is fenced to contro access and the waste is covered with soi at the end of each day. This prevents the waste being bown around, stops fies breeding on the waste, makes it ess accessibe to scavenging animas and prevents the waste catching fire. A controed andfi site is staffed, and some machinery (such as a tractor) is avaiabe to spread, compact and cover the waste with soi. The nationa Urban Soid Waste Handing and Disposa Strategy (MUDHC, 2015) incudes standards for waste disposa areas of different categories of town and city. The standard for smaer cities and towns requires that the site shoud: accommodate up to 50 metric tons of waste daiy have an inet road, which is kept repaired make sure that dumped waste is covered with soi have procedures for controing the waste coming to the site have ight machinery, such as tractors, reguary on site have an additiona 15% and area for operating space and site services forbid the disposa of rubber products, industria wastes, medica and hazardous wastes, and keep construction waste separate from genera waste. 7 of 19 Wednesday 30 March 2016

8 10.2 Landfis Note that the standard specificay mentions the probem of rubber products, which generay refers to vehice tyres. Tyres shoud not be added to andfi for severa reasons: they cannot be compacted; they may coect water which creates a breeding site for mosquitoes; and, if they catch fire, they can burn for many weeks or even months. Foowing these standards is good practice in sma and medium-sized towns, but continuous staffing is needed to contro how and where the waste is deposited and to prevent the site from becoming an open dump. Furthermore, there is no contro of eachate being formed or contaminating ground and surface waters Sanitary andfi A sanitary andfi is an engineered faciity for the disposa of waste from arger towns and cities (Figure 10.3). To be cost-effective there needs to be more than around 150 metric tons of waste deposited in a day. The site is designed and operated to minimise pubic heath and environmenta impacts. The additiona environmenta contro measures shoud incude a system to coect and treat eachate, better gas venting systems and good amenities for site staff. In Figure 10.3 you can see the drainage channes for eachate that have been prepared before the waste is added to the area in the foreground. Larger sites shoud be divided into ces separated by earth banks. Adding waste to one ce at a time aows each part of the site to be fied and covered more quicky. Figure 10.3 A sanitary andfi. For the argest cities, the idea sanitary andfi woud aso have: 8 of 19 Wednesday 30 March 2016

9 10.3 Panning controed andfis for sma and medium-sized towns an active system to pump out andfi gas and burn it, ideay making use of the heat generated a iner made of compacted cay or a synthetic membrane sheet that separates the waste from the ground beow and prevents eachate eaking from the site and into the surrounding ground. These types of andfi sites are uncommon in African countries, but efforts are being made to convert the Repi andfi in Addis Ababa into a sanitary andfi. According to the data in Study Session 7, typica waste generation rates in Ethiopia are between 0.3 kg and 0.5 kg per person per day. If you assume a rate of 0.3 kg, how big a popuation woud a city need for it to operate a sanitary andfi? To be cost-effective, a sanitary andfi needs to take at east 150 metric tons of waste a day, which is 150,000 kg. If a this waste came from residentia sources, this woud need: peope 10.3 Panning controed andfis for sma and medium-sized towns If sma and medium-sized towns wish to reduce open dumping, a dedicated controed andfi site needs to be identified and deveoped. To pan for a new site, two key factors to consider are the area of and required and the choice of the best ocation Estimation of the required and area As an exampe, think of a town with a popuation of 25,000 peope that produces around 4000 metric tons of waste a year (residentia, commercia and industria). The town intends to construct a controed andfi that wi ast for five years. The first stage is to estimate the voume of space that this waste wi occupy. From previous experience, it is known that one cubic metre (1 m 3 ) of waste weighs about 600 kg when andfied; in other words the density of waste is 600 kg per m 3. So one year s worth of waste (4,000,000 kg) wi occupy: m 3 Therefore five years waste wi need m 3. But we aso need to aow for the soi that is used to cover the waste. Again, from experience, it is known that this wi add about 10% to the space required. In this case we wi need: m 3 We now need to cacuate the and area. If we assume that the depth of the waste and soi cover in the site wi be 3 m, the site area required wi be: m 2 Athough this is the requirement for the and used for disposa, additiona and is required to give space for vehices to move, for the cover soi to be stored and for an amenity 9 of 19 Wednesday 30 March 2016

10 10.4 Therma processing methods buiding. From Section , this wi account for a further 15%, so the site area becomes: m 2 If the site were rectanguar, a space of 100 m by 140 m woud be suitabe Finding a suitabe ocation Once the area of and is known, the next step woud be to find a suitabe ocation. The main factors in deciding if a site is suitabe are as foows: How far is the site from the centre of the popuation? On the one hand, if the site is too cose, the peope may be bothered by odours. However, if the site is more than about 3 km from the town, a transfer station (see Study Session 9) wi be needed to transfer the waste from the coection vehices to a orry that then takes the waste to the site. Is the site near a watercourse? Generay speaking it is better to avoid an area cose to fowing water because there is aways a risk that eachate wi eak from the site. It may be tempting to use a dry vaey but this may not be dry during the rainy season and running water coud carry the andfied waste over a arge area. For this reason, vaeys are best avoided. Is there any groundwater under the site? It is important to take speciaist advice about this because of the risk of contamination. What is the oca soi type? Water and eachate fows through different sois at different speeds. Sandy sois tend to be very permeabe and eachate wi fow through them quicky and for a ong distance. Cay sois tend to be ess permeabe so eachate traves sowy and for shorter distances through them. What do the oca community think about it? Some areas of and are considered to be sacred by one or more reigious groups and shoud never be considered for andfi. Using such and woud be deepy offensive to the peope concerned Therma processing methods Therma processing of waste means heating waste so that it burns. During the burning (aso known as combustion) process, the combustibe materia is converted into gases (mainy carbon dioxide and water vapour) and an ash residue. Therma processing eads to a arge reduction in the voume of soid materia eft over for andfi disposa and destroys pathogens, so it may ook ike an attractive option. However, uness the combustion takes pace under tighty controed conditions using equipment designed to prevent and capture any poutants produced, the process wi emit a arge amount of smoke and other invisibe air poutants that can cause serious heath probems. There are two main therma processes you may come across: open burning; and incineration. There are other more advanced therma processing methods but these are not currenty used in Ethiopia. 10 of 19 Wednesday 30 March 2016

11 10.4 Therma processing methods Open burning Many individua househoders practise open burning in their yards, where waste is burned in a pie in the open air and the remaining ash is buried or spread on the ground. This may be easier for the househoder than taking their waste to a coection point or a andfi, but the smoke is an annoyance to the neighbours and can be a heath hazard (Figure 10.4). You shoud aways discourage open burning uness it reay is the ony option for deaing with the waste. Figure 10.4 Open burning produces a ot of smoke and can be dangerous Incineration Incineration, as opposed to open burning, is the combustion of waste materia in an encosed container with an air suppy and ideay fitted with a chimney. The combustion process can be controed to some extent so ess poution is produced and a chimney heps to reduce the impact by sending product gases upwards into the atmosphere. An incinerator of the type that may be used in arge schoos or hospitas is shown in Figure 10.5(a). Smaer, ower-cost incinerators may be buit from bricks (Figure 10.5(b)). These can be buit ocay and are the type you are most ikey to see. 11 of 19 Wednesday 30 March 2016

12 10.5 Types of hazardous waste Figure 10.5 (a) A meta incinerator with a chimney. (b) A brick incinerator is simper and cheaper to buid. Incinerators are mosty used in Ethiopia to treat heathcare waste or waste in other institutions such as schoos. They are preferabe to open burning but they sti generate smoke and other poutants. They need to be operated with care to make sure they function correcty and to minimise possibe poution. Good practices in managing sma incinerators incude the foowing: Make sure there is a sufficient air suppy to the container where the burning takes pace. Usuay the air fows upwards through the chamber, so the bars that the burning waste sits on shoud not be bocked. Most poution is formed when the incinerator is heating up, so use firewood or cean, dry waste at the start. Waste shoud be added to the incinerator reguary so that the temperature does not fa and cause smoke to be formed. Generay, wet waste shoud be added in sma amounts and ideay mixed with dry waste. The ash shoud be removed when cod and then buried. Care must be taken to avoid ight ash bowing away in the wind. The incinerator shoud be in a fenced-off area when operating, the externa surfaces wi become very hot. The incinerator operators shoud be trained adequatey. They shoud wear protective cothing (goves, face masks, etc.), especiay when burning heathcare waste. They shoud have access to and use handwashing faciities at the end of each shift and before mea breaks Types of hazardous waste Hazardous waste was defined in Study Session 7 as any discarded materia that may pose a substantia or potentia threat to pubic heath or the environment. Hazardous 12 of 19 Wednesday 30 March 2016

13 10.5 Types of hazardous waste waste, whether iquid or soid, must be kept separate from non-hazardous waste and requires specia handing and treatment. Hazardous wastes may be: Toxic these are wastes that are capabe of causing acute or chronic heath probems. Exampes incude asbestos, arsenic, heavy metas and synthetic pesticides. Ignitabe ignitabe wastes wi catch aight very easiy when exposed to a fame or spark. Ignitabe wastes are aso highy fammabe meaning they burn easiy. Exampes are organic sovents, ois and paint wastes. Corrosive corrosive substances that are strongy acidic (ph ess than 2) or strongy akaine (ph higher than 12.5), and can readiy dissove standard container materias or damage iving tissue. Exampes incude acids, akais, ceaning agents and discarded batteries or battery manufacturing residues. Reactive reactive wastes are dangerous because of their vigorous reaction with air and water, or because they can expode and generate toxic fumes. Exampes are obsoete munitions, wastes from manufacturing dynamite or firecrackers, and some chemica wastes. Infectious any waste that contains micro-organisms that can harm humans. Much of the waste produced by hospitas, heath centres and dentists may we be infectious. This type of waste may aso be referred to as a biohazard. Which of the foowing waste materias coud be considered to be hazardous? 1 food waste 2 discarded mobie phones 3 used gas canisters 4 schoo aboratory waste 5 od medicines and drugs. A of these waste materias, apart from food waste, shoud be considered hazardous. How do you know whether a waste is hazardous? Many hazardous products are found in Ethiopia but peope do not aways know how to identify them. It is important that anyone who comes in contact with hazardous materias understands their nature so they can protect themseves and hande the specific product or waste with care to avoid damage to skin, cothes or even property and ife. There is an internationay agreed set of hazard symbos, shown in Figure of 19 Wednesday 30 March 2016

14 10.5 Types of hazardous waste Figure 10.6 Hazardous waste symbos Househod hazardous waste You may think that hazardous waste is ony produced in factories and hospitas, but you shoud be aware of househod hazardous wastes. These are wastes produced in norma househods that have any of the hazardous properties isted above. This coud incude beaches and some ceaning products, batteries, paints, pesticides, and pharmaceuticas (Figure 10.7). 14 of 19 Wednesday 30 March 2016

15 10.6 Management of hazardous waste Figure 10.7 Some harmfu chemicas that can be found in our homes Management of hazardous waste When it comes to treating hazardous wastes, the principe of the 3 Rs shoud be foowed where possibe. Aongside reduction, repacement shoud aso be practised as the first stage in the waste hierarchy. This means repacing hazardous substances with nonhazardous ones in manufacturing processes and avoiding processes that produce hazardous by-products. Appying the 3 Rs to hazardous waste is highy speciaised and woud normay be the responsibiity of the industries concerned. There are a number of options for treating hazardous waste, based on transforming it to a non-hazardous form or isoating it from peope and the environment. The options are: Secure andfi, where the waste is competey isoated from the environment. This is generay the safest method, but sites that are designed to take hazardous waste are uncommon in Africa. Treating the hazardous waste chemicay to transform it into a non-hazardous waste. For exampe, acid waste can be neutraised by the addition of the correct amount of an akai. 15 of 19 Wednesday 30 March 2016

16 Summary of Study Session 10 Treating organic hazardous wastes (ois, for exampe) with micro-organisms to break them down into non-hazardous materias. Controed high-temperature incineration of fammabe wastes (ois and chemicas) and medica wastes. However, the process needs to be very carefuy controed and carried out in a purpose-designed incinerator. In reaity, much of Ethiopia s hazardous waste, aong with other wastes, is disposed of in andfi sites. This does give some isoation from peope and the environment in the short term, but you must be aware that this means that a andfis shoud be treated as containing hazardous waste and a possibe steps shoud be taken to keep peope away from these sites. Summary of Study Session 10 In Study Session 10, you have earned that: 1 Soid waste that cannot be recyced can be treated or disposed of by andfi or therma processing. 2 The two main environmenta probems from andfi are eachate, which can contaminate water sources, and andfi gas, which is a greenhouse gas and is fammabe. 3 Landfis range from uncontroed open dumps to sanitary andfis, where eachate and andfi gas are managed and controed. 4 Factors to be considered when seecting a new andfi site incude the area of and required, distance from the town, potentia for poution of water sources, soi type and oca cuture and beiefs. 5 The open burning and open dumping of soid waste, which is a common practice in many urban centres in Ethiopia, is dangerous to human heath and safety and to the wider environment. 6 Incineration reduces the voume of waste for disposa, but the remaining ash sti needs to be andfied. 7 It is important to know the nature and characteristics of soid waste, to recognise hazardous waste, and to appreciate how it shoud be handed and treated. Sef-Assessment Questions (SAQs) for Study Session 10 Now that you have competed this study session, you can assess how we you have achieved its Learning Outcomes by answering these questions. 16 of 19 Wednesday 30 March 2016

17 Sef-Assessment Questions (SAQs) for Study Session 10 SAQ 10.1 (tests Learning Outcomes 10.1 and 10.2) Which of the foowing waste disposa methods woud you consider to be the safest to pubic and environmenta heath? Expain the reasons for your choice and why the other two options are ess desirabe. (a) (b) (c) Disposa into open fied away from residentia areas. Disposa into a river. Disposa in a sanitary andfi. Answer Option (c), sanitary andfi, is the safest option. (a) (b) (c) The open fied is away from residentia areas so odour may not be a probem but it woud attract fies, rats and other scavengers. The waste is not covered so it coud be bown around by wind or burn uncontroaby. Leachate from the waste coud poute water sources and there woud be no contro of andfi gas. Discarding waste into a river coud cause a the above probems and woud certainy poute the river water which coud affect peope using the river as a water source for themseves, their animas or for irrigation. Poution woud aso affect widife both in and around the river. A we-managed sanitary andfi is the safest option because this woud ensure eachate was coected and treated and woud contain and contro andfi gas. The waste woud be covered every day with soi to stop it bowing around, prevent fy breeding, discourage scavenging animas and prevent the waste from catching fire. SAQ 10.2 (tests Learning Outcomes 10.1 and 10.2) If a community wanted to transform its open dump site into a controed andfi, what measures woud it have to take? Answer Measures to transform an open dump site into a controed andfi shoud incude: surrounding the site with a chid-proof and anima-proof fence empoying a person to staff the site providing a tractor to spread and compact the waste covering the freshy deposited waste with a ayer of soi each day. SAQ 10.3 (tests Learning Outcomes 10.1 and 10.2) Expain how incineration differs from open burning. Answer Incineration is burning that is encosed and controed. Open burning is uncontroed. Incineration produces ess smoke; the ash is contained and can be removed for buria; it is safer because the burning waste cannot be bown around and spread fire. A higher 17 of 19 Wednesday 30 March 2016

18 Sef-Assessment Questions (SAQs) for Study Session 10 temperature can be maintained in an incinerator which ensures more of the waste is consumed, eaving itte residue. SAQ 10.4 (tests Learning Outcomes 10.3) What are the key factors to be considered when panning a new andfi in sma and medium-sized towns? List at east four factors. Answer Key factors to consider when panning a andfi in sma and medium-sized towns incude: avaiabe and required and area based on popuation size, both current and future, and estimated waste production rate distance from the site to the town to be served ocation of rivers that coud be pouted presence of groundwater beow the site soi type and geoogy oca opinions and beiefs about the site. SAQ 10.5 (tests Learning Outcomes 10.1 and 10.4) (a) (b) Identify the type of hazardous waste of each of the foowing: od batteries from wrecked cars and orries firecrackers that were thrown away because they got damp empty pesticide can boody bandages from a heath centre iquid waste from a factory with ph 13 used sovent from ceaning paint brushes. State four ways in which hazardous waste can be disposed of safey. Answer (a) The types of waste and their corresponding hazards are: Type of waste Od batteries from wrecked cars and orries Firecrackers that were thrown away because they got damp Empty pesticide can Boody bandages from a heath centre Liquid waste from a factory with ph 13 Used sovent from ceaning paint brushes Type of hazard Corrosive Exposive or fammabe Toxic Infectious Corrosive Ignitabe and fammabe 18 of 19 Wednesday 30 March 2016

19 Sef-Assessment Questions (SAQs) for Study Session 10 (b) Depending on the type of hazard, safe disposa methods of hazardous waste incude: disposing of the waste in a secure andfi where the waste is kept competey isoated from the genera environment subjecting it to various chemica treatment methods controed incineration at a high temperature bioogica treatment using specific micro-organisms. 19 of 19 Wednesday 30 March 2016