Study Session 4 Water Pollution

Transcription

1 Study Session 4 Water Poution Copyright 2016 The Open University

2 Contents Introduction 3 Learning Outcomes for Study Session Pathways of water poution Types of water poutant Sediments and suspended soids Organic matter Bioogica poutants Pant nutrients Other chemica poutants Possibe sources of water poution Human excreta Manufacturing and industria pants Agricuture and anima rearing Domestic and industria soid waste sites Urban surface water run-off Protection from poution Monitoring and reguation 15 Summary of Study Session 4 16 Sef-Assessment Questions (SAQs) for Study Session of 21 Tuesday 29 March 2016

3 Introduction Introduction You have aready earned about some of the ways how surface and groundwater can become contaminated and about the importance of water treatment to make the water safe to drink. There are different types of poutants from a variety of sources that can harm the quaity of water. In this study session you ook more cosey at these poutants, where they originate from and their effects. You aso consider how water sources can be protected from poution. Learning Outcomes for Study Session 4 When you have studied this session, you shoud be abe to: 4.1 Define and use correcty a of the key words printed in bod. (SAQ 4.1) 4.2 Describe the different types of water poutants. (SAQ 4.2) 4.3 Expain the possibe ways in which water can be pouted. (SAQs 4.2 and 4.3) 4.4 Describe measures that can be adopted for protecting water sources from poution. (SAQ 4.4) 4.1 Pathways of water poution Poution can be defined as the introduction into the natura environment (air, water or and) of substances (poutants) that are iabe to cause harm to human heath or to animas, pants and the wider environment. Water poution occurs when surface water or groundwater is adversey affected by the addition of poutants. For surface water, the quaity of the water wi be determined by the geoogy, by precipitation and by what happens in the catchment. The catchment of a river is the tota area of surrounding and that sopes towards the river (Figure 4.1). Rainwater that ands in a catchment fows into the river. River water can be contaminated from poution sources in the catchment even though they may be some distance away. Protecting surface water from poution is difficut because the activities of upstream users of river water wi affect the quaity of the water for downstream users. For groundwater, the situation is simiar but the boundaries are ess distinct and poutants can seep into aquifers that extend beow more than one catchment. 3 of 21 Tuesday 29 March 2016

4 4.1 Pathways of water poution Figure 4.1 A mode of a catchment area. Water quaity can be affected by poution from point sources and non-point sources. Point sources are identifiabe ocations (such as a factory, often with a pipe or channe eading from them) that discharge directy into a body of surface water. Groundwater is aso affected by point sources where contaminants seep into the soi and rock from an identifiabe source, for exampe, underground fue tanks, septic tanks or pit atrines. Nonpoint sources are those where poution arises over a wide area and it is often difficut to ocate the exact pace of origin. For exampe, fertiiser or pesticide that has been widey spread may be washed from a fied by rain into a river or stream at many paces, or seep into groundwater. It is poution from non-point sources, aso known as diffuse poution, that contributes most of the contaminants in surface and groundwater. The probems in identifying the exact point of origin make non-point sources much more difficut to contro. Look at Figure 4.2. What poutants are ikey to be washed into the river from the orry? Is this a point source or non-point source of poution? Dust and dirt from the orry wi be washed into the river. Some oi and fue may aso be washed from the underside. The orry is the singe source of poution, so this is an exampe of a point source. 4 of 21 Tuesday 29 March 2016

5 4.2 Types of water poutant Figure 4.2 Washing orries and cars in rivers is a source of water poution. The norma fow of river water can reduce the impact of some poutants. When contaminated river water moves downstream it is possibe that any poutant wi be diuted as more water fows in and so increases the tota voume of water in the river. This diution may be enough to reduce the concentration of the contaminants sufficienty to minimise the possibe impacts, but this depends on severa factors, incuding the quantity and type of poutant, and the voume and fow rate of the river. 4.2 Types of water poutant There are many different types of water poutant and the foowing sections describe those that are most commony found Sediments and suspended soids Sediments and suspended soids consist of fine partices of mosty inorganic materia. Inorganic materia is derived from non-iving sources and incudes mud, sand and sit washed into a river as a resut of and cutivation, construction, demoition and mining operations, where these take pace. One of the most common sources of suspended soids and sediment is soi erosion, where the soi is washed away into rivers by 5 of 21 Tuesday 29 March 2016

6 4.2 Types of water poutant rainwater run-off. The presence of soid particuate materia suspended in the fowing water is the reason why many rivers ook brown in coour, especiay in the rainy season. The partices are caed suspended soids whie they are carried (suspended) in fowing water and sediments when they sette to the bottom. Large quantities of suspended soids may reduce ight penetration into the water, which can affect the growth of pants. Sediments may even suffocate organisms on the river bed Organic matter Organic matter, such as human and anima wastes, is derived from iving organisms. As organic matter decomposes, it removes oxygen from the water and this can have a damaging effect on fish and other aquatic organisms that are sensitive to poor water quaity. Box 4.1 expains this process. If a arge quantity of organic matter is present in surface water, this can ead to anaerobic conditions. (Anaerobic means without oxygen, as opposed to aerobic, which means oxygen is present.) In this situation many aquatic organisms are unabe to survive and the water wi be stagnant and sme unpeasant. Box 4.1 Oxygen in water Many aquatic (water-iving) organisms depend on oxygen dissoved in the water to survive. Aquatic animas incude fish, amphibians and many invertebrate species such as insect arvae, snais and worms. Their suppy of oxygen in the water is maintained from atmospheric oxygen in the air above the water and from oxygen produced by green aquatic pants by the process of photosynthesis, the process by which pants convert ight energy into chemica energy, whie taking in carbon dioxide from the atmosphere and producing oxygen. Fast-fowing, turbuent water wi be aerated (gain oxygen) more than sti water because the turbuent fow wi entrain more oxygen. If organic poutants such as human and anima wastes are reeased into a water body, bacteria wi use the waste as food and break it down into simper, ess harmfu substances. As they do this, aerobic bacteria wi use up the dissoved oxygen from the water. This is caed deoxygenation. If the degree of organic poution is high, then a the oxygen from the water may be used up, eading to anaerobic conditions. This is unikey in a river where the water is moving but can happen in akes or sow-fowing channes. Inorganic soids, such as mud and sit, do not have this effect because they are inert (stabe and inactive) and cannot be used as food by bacteria Bioogica poutants You have aready earned about bioogica poutants in Study Session 2. These are the infectious agents (bacteria, viruses, protozoa and heminths) that are harmfu to humans and other forms of ife. Bioogica poutants may get into water with dust from the air as rain fas but the most ikey source is from water that is contaminated with human and anima wastes. 6 of 21 Tuesday 29 March 2016

7 4.2 Types of water poutant Pant nutrients Nitrates and phosphates are common poutants generated from residentia areas and agricutura run-off. They are usuay associated with human and anima wastes or fertiiser that has been washed into surface water bodies by rain. Nitrates and phosphates are pant nutrients, so they stimuate pant growth. If present in arge quantities, they can encourage excessive pant growth in the water causing the phenomenon known as an aga boom, which means a sudden increase in the popuation of microscopic agae (simpe pants). There may aso be an increase in arger pants such as the invasive water hyacinth. When the increased popuation of aquatic pants dies, the decay of the organic pant materia by bacteria can cause deoxygenation of the water, resuting in the death of other organisms such as fish. If a water body has high nutrient eves it is said to be eutrophic and the process is known as eutrophication. Figure 4.3 iustrates the process. Figure 4.3 The eutrophication process. Can you think of a reason why eutrophication is more ikey to be a probem in akes than in rivers? Because fowing water in a river wi disperse the nutrients; in the sti water of a ake, the nutrients wi accumuate. In Ethiopia, many private and corporate farms use huge amounts of chemica fertiisers. As a resut, eutrophication is becoming a major probem (Zinabu et a., 2002), affecting many water sources (Figure 4.4). 7 of 21 Tuesday 29 March 2016

8 4.2 Types of water poutant Figure 4.4 Lake Hawassa, in the Rift Vaey, south of Addis Ababa, is suffering from eutrophication Other chemica poutants Heavy metas such as arsenic, copper, ead, mercury and cadmium are chemica poutants that may be found in akes, rivers and groundwater. These heavy metas can harm aquatic organisms and humans. Farmers who use river water pouted by urban wastes for irrigation in the cutivation of fruits and vegetabes may find their crops affected by the accumuation of these chemicas. (You wi ook at a case study on this ater on in this study session.) Pesticides incude insecticides, herbicides and fungicides. There are severa thousand different types in use and amost a of them are possibe causes of water poution. Pesticides such as DDT (dichorodiphenytrichoroethane), maathion, parathion and others have been sprayed in the environment for ong periods of time for the contro of disease vectors such as mosquitoes and other pests. Heavy metas and some pesticides are particuar probems because they are persistent in the environment, meaning they do not break down and their effects continue over time, even ong after their use may have stopped. Another probem can be acidity. If water becomes acidic or akaine, beyond norma imits, this wi have a damaging effect on aquatic organisms. Acidity and akainity of water are determined by measuring its ph. A ph vaue beow 7 is acidic and above 7 is akaine. 8 of 21 Tuesday 29 March 2016

9 4.3 Possibe sources of water poution Acidic water is not ony harmfu to ife but is aso corrosive and can damage pipework in water distribution systems. 4.3 Possibe sources of water poution Having ooked at the various types of poutant, et us now consider their sources Human excreta Open defecation and poory constructed pit atrines are obvious sources of human waste and can easiy poute surface and groundwater. Where water-fushed sewerage systems are present, inadequatey treated sewage can aso be a major source of human waste. (Note the difference between the words sewage and sewerage. Sewage is mixed wastewater that contains human waste from fush toiets, commercia and industria wastewater, and frequenty aso surface water run-off. Sewerage is the network of underground pipes sewers through which the sewage fows.) Untreated or partiay treated sewage can contribute to high eves of oxygen demand in the water and aso introduce toxic substances into the aquatic environment, in addition to pathogenic micro-organisms. In Ethiopia, sewage may be treated in waste stabiisation ponds (these wi be described in Study Session 11). If not operated propery, these ponds can poute rivers. In many parts of the word, sewage from arge towns and cities is usuay treated in arge mechanica bioogica pants (Figure 4.5) that normay produce good quaity effuent but can sti be a source of poution if systems fai. 9 of 21 Tuesday 29 March 2016

10 4.3 Possibe sources of water poution Figure 4.5 Becton sewage treatment pant in London, the argest pant of its type in Europe, treats the sewage of 3.7 miion peope. In Ethiopian towns and cities many househods use septic tanks to dispose of their sewage. These are underground tanks into which sewage is piped. The waste remains in the tank for ong enough for the soids to sette out and the setted sewage is discharged from the tank, usuay into the surrounding soi via a soakaway. If the tank is too sma to retain the sewage for ong enough, or if many septic tanks are cose together, or if they eak or are cracked, this can ead to poution of groundwater. It is the aim in Ethiopia to have septic tanks that keep the sewage inside for a minimum of three days so that the organic soids wi sette out as sudge. Figure 4.6 shows the main features of a propery constructed septic tank. 10 of 21 Tuesday 29 March 2016

11 4.3 Possibe sources of water poution Figure 4.6 Cross-sectiona diagram of a septic tank Manufacturing and industria pants In Study Session 1 you read about some of the ways in which water is used in industry and manufacturing. The range of different uses and processes can produce waste in the form of many different types of organic and inorganic materia in suspension or in soution. In many cases, much of the water used can be recyced but there is amost aways an effuent discharge that requires treatment. Food processing generates arge voumes of effuent containing natura organic compounds such as carbohydrates, proteins and fats. Factories producing chemicas often generate ow voumes of highy toxic waste streams. Toxic effuents can aso be produced in the paper, eather and eectropating industries. For exampe, cyanides and heavy metas may be present in wastewaters from eectropating. These pants can aso be the source of highy acidic wastes. Manufacturing and industria effuents shoud be treated at their points of origin but many production pants in Ethiopia (such as tanneries and breweries) do not have proper effuent treatment systems. This resuts in the discharge of untreated or partiay treated effuent into the nearest water body (Figure 4.7). 11 of 21 Tuesday 29 March 2016

12 4.3 Possibe sources of water poution Figure 4.7 Industria discharge into the Akaki River in Addis Ababa Agricuture and anima rearing The intensive rearing of animas resuts in arge voumes of organicay pouted washwater from ceaning anima houses. This surry is often stored in agoons or tanks prior to spreading on and. However, probems occur when these agoons or tanks eak or overfow, aowing the surry to fow into watercourses or infitrate groundwater. Other agricutura poutants incude pesticides and fertiisers. Cutivation and overgrazing can make soi erosion more ikey, resuting in soi partices being washed into rivers and akes. For exampe, this is a probem at Gondar, where runoff from the surrounding and has washed sit into the reservoir, thus reducing the voume of water it can hod (Figure 4.8). 12 of 21 Tuesday 29 March 2016

13 4.3 Possibe sources of water poution Figure 4.8 The Angareb reservoir at Gondar Domestic and industria soid waste sites Domestic and commercia soid waste shoud be disposed of in a propery designed and constructed andfi site. Many andfi sites, particuary those that are oder and ess we designed and managed, such as the one shown in Figure 4.9, generate eachate, which is highy pouting. (Leachate is any iquid that has passed through matter and picked up dissoved substances and/or suspended soids as it passed through.) Leachate can contain dissoved organic matter and many different types of inorganic components depending on the type of waste. Where industria waste has been dumped, a toxic chemica stream may aso be produced. These eachates shoud be coected and treated so that poution of groundwater and rivers does not arise. 13 of 21 Tuesday 29 March 2016

14 4.3 Possibe sources of water poution Figure 4.9 The andfi site at Repi, Addis Ababa Urban surface water run-off Rainwater that runs off road surfaces, roofs, parking areas, etc. carries with it a variety of components (Tabe 4.1). The buk of the contaminants can be traced to motor vehices. Surface water run-off can cause damage to streams, rivers and akes by degrading the water quaity and harming aquatic ife. The poutants present can hinder the growth and reproduction of fish and other creatures, and affect photosynthetic activity. Pant nutrients may contribute to eutrophication. Tabe 4.1 Poutants that may be present in rainwater run-off. Poutant Sediment Copper Lead Zinc Hydrocarbons Rubber Detergents Litter Likey sources Construction, road surfaces, emissions from vehices, industria sources, vehice wear Vehice brake pads, industria activities, pumbing and guttering Industria activities and residues from historica activities (pumbing, paint, eaded petro, sprays), tyre-baancing weights, vehice brake pads Vehice tyres, gavanised buiding materias, paint, industria activities Vehice emissions, ubricating ois Tyre wear Wash-down areas, domestic discharges (e.g. from car washing), industria discharges Discarded materia (e.g. pastic bags, cups, cigarette ends), windbown materias, iega dumping 14 of 21 Tuesday 29 March 2016

15 4.4 Protection from poution 4.4 Protection from poution The contro of poution shoud ideay take pace at the point of its generation. In Study Session 3 you read about the methods of protecting water sources but it is better to prevent the poutant from entering the environment in the first pace. With regard to human excreta, this means an end to open defecation, the correct siting and construction of atrines and septic tanks, and we-maintained and correcty operated sewage treatment works. Industria wastes shoud be treated at source before discharge. Other human activities shoud aso be controed; for exampe, used engine oi shoud not be thrown onto the ground, and soid wastes shoud be carefuy disposed of. A positive measure that can hep to prevent soi erosion is to preserve vegetation and pant trees, because pant roots hod the soi in pace. In rura areas, the contro of excess nutrients is important to keep natura waters free from eutrophication. Farmers may need guidance on good agricutura practices to reduce water poution from agricuture. For exampe, care over the amount of fertiiser used and the timing of its appication can make a significant difference. Imagine you are a farmer thinking about the best time to appy fertiiser to your fied. Woud it be better to spread the fertiiser before or after heavy rain? It woud be better to appy it after the rain because if the fertiiser was spread beforehand, much of it woud probaby be washed away. This woud not ony poute the nearest river but woud, of course, aso reduce its effectiveness on the crop. Pesticides shoud not be appied near wes or other water sources. If possibe, bioogica methods of pest contro shoud be used. Exampes of these are the use of fish to feed on mosquito arvae in water bodies, and the use of the dung beete to break down and bury cow faeces so that they are no onger avaiabe as a breeding pace for fies. Ideay, the whoe catchment area shoud be managed to avoid poution and erosion. To tacke poution probems, especiay diffuse poution, a activities within a catchment shoud be considered. This invoves many groups (residents, panners, farmers, etc.) working together, on aspects such as granting permissions for deveopment, compiance with reguations, inspections of activities, and reguar surveys and investigations of water poution. 4.5 Monitoring and reguation Monitoring of the quaity of rivers (Figure 4.10) can be done at reguar intervas by taking sampes for aboratory anaysis. In Ethiopia this activity is undertaken by the Ministry of the Environment and Forests. In addition to this, reguar surveys of a catchment area are usefu so that potentia poutants can be identified before they contaminate a water source. 15 of 21 Tuesday 29 March 2016

16 Summary of Study Session 4 Figure 4.10 A technician monitoring water quaity. For effective protection of water sources, it is important to estabish a reguatory framework for treatment of wastewater from residentia communities, institutions and industries. Strict egisation shoud be in pace to make it obigatory for wastewaters to be treated before discharge into rivers or akes. Ethiopia has the Ethiopian Water Resources Management Reguations (Counci of Ministers, 2005). Part 4 of these reguations states that a permit to discharge wastewater must be obtained for the direct or indirect discharge of any treated trade effuent or sewage effuent, or any poisonous, noxious or pouting matter into surface or ground water. Anyone who obtains the permit has an obigation to insta and use the best treatment method and to discharge ony the type and voume of treated waste permitted. Contro of water poution is the responsibiity of more than one organisation, since most activities invoving water concern a number of different Ministries. For instance, water use in agricuture woud be of concern to the Ministry of Agricuture, the Ministry of Water Resources, Irrigation and Energy, and the Ministry of the Environment and Forests, and a of them have the responsibiity of protecting the environment. Summary of Study Session 4 In Study Session 4, you have earned that: 1 Water poution is any contamination of water with substances that are detrimenta to human, pant or anima heath. 2 Water poutants can be of point or non-point source, depending on whether substances are discharged directy into a body of water or indirecty from diffuse sources. 3 Water poutants incude sediments and suspended soids, organic matter, bioogica poutants, pant nutrients and chemica poutants. 16 of 21 Tuesday 29 March 2016

17 Sef-Assessment Questions (SAQs) for Study Session 4 4 Bioogica poutants incude bacteria, viruses, protozoa and heminths. They mainy enter the water through faeces from infected peope and animas, and are the cause of many water-reated diseases. 5 Major sources of water poution incude human excreta; manufacturing and industria pants; anima rearing and agricutura activities; andfi sites; and urban surface water run-off. 6 Measures to protect water sources from faeca poution incude ending open defecation, the proper siting of atrines and septic tanks, and carefu operation of sewage treatment works. 7 The appropriate use of fertiisers and pesticides wi minimise water poution caused by agricuture. 8 Seective panting of trees and vegetation can hep stabiise soi and prevent erosion. 9 Poution contro shoud ideay take pace at the point of origin. 10 Reguations contro the type and voume of treated effuent that may be discharged to the environment. Sef-Assessment Questions (SAQs) for Study Session 4 Now that you have competed this study session, you can assess how we you have achieved its Learning Outcomes by answering these questions. SAQ 4.1 (tests Learning Outcome 4.1) Match the foowing words to their correct definitions. eutrophication a process by which a high concentration of nutrients, especiay phosphates and nitrates from agricutura or other activities, enters a water body and ead to excessive pant growth and eventua decay, resuting in depetion of oxygen in the water aerobic containing oxygen organic matter materia that comes from iving organisms septic tank an underground tank into which sewage is piped point-source of poution an identifiabe source of poution soi erosion the washing away of soi by rainwater run-off inorganic materia materia which does not originate from iving organisms sewerage 17 of 21 Tuesday 29 March 2016

18 Sef-Assessment Questions (SAQs) for Study Session 4 a network of sewers aga boom a sudden increase in the aga popuation non-point source of poution a source of poution that encompasses a wide area, the exact point of origin being difficut to ascertain suspended soids partices carried in fowing water poution the introduction into the environment of substances ikey to cause harm to humans, animas, pants and the environment in genera poutants substances that can cause harm to human heath, pants, animas and the environment in genera sewage mixed wastewater that contains human waste from fush toiets diffuse poution poution from non-point sources catchment the area of surrounding and that sopes towards a river sediments soids that have setted at the bottom of a river eachate a pouting iquid that is produced when water passes through materias and takes with it components from them anaerobic without oxygen photosynthesis the process by which pants generate chemica energy SAQ 4.2a (tests Learning Outcome 4.2) Cassify the foowing exampes of water poutants using the categories shown in the tabe beow: copper insecticides sand protozoa nitrates bacteria ead sit phosphates 18 of 21 Tuesday 29 March 2016

19 Sef-Assessment Questions (SAQs) for Study Session 4 faeca matter intestina worms Category of water poutant Exampes Sediments and suspended soids Organic matter Bioogica poutants Pant nutrients Other chemica poutants Answer The answer is as foows: Category of water poutant Sediments and suspended soids Organic matter Bioogica poutants Pant nutrients Other chemica poutants Exampes sand, sit faeca matter bacteria, protozoa, intestina worms nitrates, phosphates copper, ead, insecticides SAQ 4.2b (tests Learning Outcome 4.2) The foowing are poution sources. Give two specific poutants for each source. A residentia area: A meta pating pant: Agricutura activities: An uncontroed andfi site: Urban surface water run-off: Answer There are severa possibiities, isted beow. 19 of 21 Tuesday 29 March 2016

20 Sef-Assessment Questions (SAQs) for Study Session 4 A residentia area: A meta pating pant: Agricutura activities: An uncontroed andfi site: Urban surface water run-off: human excreta, wastewater containing dissoved and suspended organic matter, suspended inorganic matter, pathogenic microorganisms cyanides, heavy metas nitrates, phosphates, pesticides eachate containing dissoved organic matter, inorganic components and heavy metas sediment, metas, hydrocarbons, rubber, detergents, itter SAQ 4.3 (tests Learning Outcomes 4.2 and 4.3) Read Case Study 4.1 and then answer the questions that foow. Case Study 4.1 Mekanisa is a pace in the southern part of Addis Ababa where urban agricuture is practised. A group of farmers grow different varieties of vegetabes and se them to peope in the city. The farmers use water from the nearest river (the River Kera) for irrigation. They mosty grow eafy vegetabes, with two harvests a year. The Kera River originates a few kiometres from Mekanisa and passes through residentia, commercia and industria areas before reaching Mekanisa. Aong its way, human excreta and industria wastes are indiscriminatey discharged into the river. One of the prominent pouters of the river is the city s biggest saughterhouse, ocated at the side of the river. Untreated wastewater from the saughterhouse is discharged into the river giving a bue-back coour to the water. Farmers ike this type of water for irrigation as it heps their crops grow. One of the authors of this Modue undertook research assessing the eve of poution of the river water. The resuts are shown in Tabe 4.2. Tabe 4.2 Anaysis of water from the River Kera. Parameters Faeca coiforms FAO* Guideine Concentrations for components in irrigation water (Pescod, 1992) River water <1000 per 100 m >2500 per 100 m Copper 0.2 mg mg 1 Zinc 2.0 mg mg 1 Iron 5.0 mg mg 1 Lead 5.0 mg mg 1 Manganese 0.2 mg mg 1 *FAO is the Food and Agricuture Organization of the United Nations. 20 of 21 Tuesday 29 March 2016

21 Sef-Assessment Questions (SAQs) for Study Session 4 (a) (b) (c) What nutrients in the river water do you think benefited the crops grown by the farmers? State which components in the river water might be harmfu to peope and give your reasons. Suggest what shoud be done regarding the poution of the River Kera. Answer (a) (b) (c) There are ikey to be nitrates and phosphates in the river water which are vita to pant growth. The presence of a high number of faeca coiformsindicates that the water is unsafe, and aso that other micro-organisms, which may be pathogenic, may be present. The concentrations of copper, zinc, iron, ead and manganese in the river water are a greater than the guideine vaues recommended by the FAO. This impies that they are harmfu. Poution contro at source is required. This woud entai treating the sewage, industria effuents and saughterhouse wastewaters before they are discharged into the river. SAQ 4.4 (tests Learning Outcome 4.3) Which of the foowing statements is fase? In each case, expain why it is incorrect. (A) (B) (C) (D) (E) LATRINES SHOULD BE SITED UP-SLOPE OF A WATER SOURCE SO THAT THEY DON T GET FLOODED. FOR THE PROTECTION OF SPRINGS, A FENCE, A DIVERSION DITCH, A WATERTIGHT CONCRETE BOX, AND A TIGHT-FITTING COVER ARE ENOUGH. FARMERS SHOULD USE THE MINIMUM AMOUNT OF FERTILISER THAT IS NECESSARY FOR THEIR CROPS, AND APPLY IT AFTER RAIN. CATCHMENT MANAGEMENT INVOLVES SEVERAL DIFFERENT ACTIVITIES TO ENSURE THAT THE INTEGRITY OF A WATER SOURCE IS MAINTAINED. TO SAVE TIME WATER POLLUTION CONTROL LEGISLATION IS BEST DRAWN UP BY ONE MINISTRY. Answer A is fase. Latrines shoud be beow a water source on soping ground otherwise seepage from the pit coud fow down into the water source. B is fase. The protection measures are correct but the cover shoud have a ock. E is fase. Water use is reevant to severa different ministries, a of which shoud be consuted when egisation is being prepared. 21 of 21 Tuesday 29 March 2016