7.3 Priority Wastes and Processes to be EnforcedThis list is selective in that attention is directed to substances that must be disposed of with great care. The criteria for selection includes the intensity of their:
Effects on health
General population exposure
Environmental effects
Environmental exposureAll wastes containing such substances should be notifiable to the inspector.
7.3.1 Polychlorinated biphenyls (PCBs)
PCBs are used in transformers, capacitors, heat transfer and hydraulic systems. The main users are the Uganda Electricity Board (UEB), and the main motor garages.
7.3.1.1 Control Measures
General measures:
a) All PCB transformers should be marked. The mark should show the PCB content in ppm.
b) All PCB transformers should be leakproof.
c) PCB transformer stations and storage sites containing 45 kg and above of PCBs should be licensed and notifiable sites.7.3.1.2 Storage
a) Establish a proper storage facility and this includes:
adequate roof and walls to prevent rain-water from reaching the stored material and items;
adequate floor with a continuous curbing (minimum 6" high). This must provide a containment internal volume twice that of the largest article to be stored;
no drain valves, floor drains, expansion joints, sewer lines or other openings that would permit liquids to flow from the curbed area;
the floor and curbing should be constructed of continuous smooth and impervious materials such as portland cement concrete to prevent penetration of PCBS; and,
the storage facility site shall be located above flood water level.b) Utilise proper PCB containers for storage; with the following:
steel drum without a removable head designed, constructed, and operated with safety requirements for flammable and combustible liquids;
manage the store in accordance with marking, record keeping, and inspection requirements;
removal from store and disposed of within 1 year.7.3.1.3 Disposal of PCBs
All PCB liquids and industrial sludges with PCB concentration of 500 ppm or greater must be incinerated.
On no account must even small amounts of spillage be flushed into the surface water drainage system, or any water courses, or sewers unless they lead to a hold- up tank or treatment plant.
Containers must be disposed of in a chemical waste land-fill provided it is drained the first place.Definitions
(a) Spill:
Intentional and unintentional and other uncontrolled discharges, where the release results into any quantity of the PCB running off or about to run off the external surface of the equipment or container; as well as contamination resulting from the release.
(b) Spill area:
The area of soil on which visible traces of the spill can be observed, plus a buffer zone of 0.05 metres beyond the visible traces.
Spills are uncontrolled discharges to the environment and should be dealt with as follows:
cleaned off to restore the site on land to its original state at the cost of the person who causes spills to occur;
cleaned up promptly. Any leaks must be cleaned up within 48 hrs from the time of discovery. The operator must show and be prepared to implement a Spill Prevention Control and Counter-measures;
all soil within the spill area must be excavated and the ground to be restored to its original configuration by back-filling the area with clean soil (less than 1 ppm of the PCB);
any contaminated indoor residential surface must be cleaned to 10 microgrammes per 100 sq. cm;
all contaminated solid surfaces must be thoroughly washed and rinsed; and
at the completion of the clean-up, the responsible party must document the clean-up with records and certification of the decontamination to be maintained for 5 years. The certification must include: source of the spill (for example, type of equipment or process);
date and time the spill occurred;
date and time the clean-up was completed;
description of the spill location;
pre-clean-up sampling data used to determine spill boundaries;
description of solid surfaces that were washed and method used;
reasons for delay in clean-up in case it was outside the 48 hrs time frame;
depth of the soil excavated and the amount of soil removed;
a certified statement signed by the responsible party stating that the clean-up requirements have been met and that the information contained in the record is true to the best of the party's knowledge.7.3.2 Asbestos
Definition:
The term asbestos means the fibrous form of mineral silicate belonging to rock forming minerals of the serpentine group, that is, chrysotile (white asbestos), and of the amphibole group, that is, actinolite amosite (brown asbestos, cummingtonite-grunerite), anthophylite, crocidolite (blue asbestos), tremolite or any mixture containing one or two of these.
Activities that give rise to asbestos waste include:
manufacture of products containing asbestos, such as asbestos cement roofing sheets and sewage pipes;
stripping, repair or maintenance of products containing asbestos, such as brake linings of motor vehicles;
demolition or repair of structures containing asbestos.All these are realised in Uganda.
Uganda ratified the ILO Convention No 172 (1986) Concerning Safety in the Use of Asbestos in 1990. The standards therefore, already set in this, have to be implemented.7.3.2.1 Disposal
It must be emphasised that the land used for asbestos waste disposal will be useless for most purposes afterwards. The choice of this land therefore, has to be made with greatest care.
The process of collection and disposal of asbestos must be done only in the presence of and supervision of a Specialist in occupational hygiene.
Health and safety at work during the disposal has to be ensured in particular:
- protective clothing to be provided and used;
- generally at high exposure, a full suit of
protective clothing including head-wear, clothing and foot-wear;
- material that is readily decontaminated, resistant to penetration and the design should be close fitting at the neck and waist, and it should not
have external pockets or other attachments that can trap asbestos;
- protective clothing should be worn only in the working area - it should never be taken home;
- respiratory protective equipment should always be used. This must be capable of reducing the level of asbestos respirable dust in the breathing zone of the wearer below 0.2 fibres/cm 3 .Information on the protection offered such as the respiratory equipment, should be provided by the manufacturer.
- Bags used to hold asbestos should be of good quality, dust-tight, adequately sealed and should not arrive at the site in a raptured/torn state. The bags should be labelled (asbestos) and with the corresponding danger symbol. The international symbol for asbestos is EC 103:
Risk phrase (R-Phrase) 103
("long or repeated exposure can cause cancer")Safety phrase (S-Phrase) 103 ("Prohibit any exposure as best as you can").
Any container used for disposal of asbestos waste should be made out of an impermeable material which is strong enough to remain dust-tight even under wet conditions. For loose fibrous waste or small fragments, double plastic bags are suitable. The inner bag should not be over-filled and each bag should be independently sealable.
An asbestos dumping-site should be covered immediately after depositing waste asbestos.
7.3.3 Organic Pesticides
Organophosphates and carbamates:
Hydrolysis using an alkaline solution with water to destroy its toxicity. The large containers of the said pesticides can also be decontaminated by treatment with alkaline water solution followed by rinsing and steam cleaning. Chlorinated hydrocarbons:
- Incineration at high temperatures.
- Where incineration is not possible, entomb the pesticide in a refractory material such as cement, ceramic or asphalt.7.3.4 Heavy Metals
These include: cadmium, chromium, copper, lead, nickel, zinc. Of particular interest for health purposes are: arsenic, antimony, mercury, selenium.
The required processes are:
precipitation of heavy metals in an insoluble non-toxic form; and
reduction of chromium(IV) to chromium(III).7.3.5 Cyanides
Oxidation of inorganic cyanides.
7.3.6 Acids and Alkalis
acid and alkali neutralisation prior to deposition. This should be done in trenches or lagoons constructed at the site;
direct disposal can only be done if the following concentrations are followed:(a) sulphuric acid - less than 20%
(b) nitric acid - less than 05%
(c) chromic acid - less than 05%7.3.7 Phenols
This also includes phenolic wastes such as cresol and xylenol. These are degraded in organic refuse under aerobic and anaerobic conditions only after long resident times (1-2 years).
The loading rate in the land-fill should be kept to 2 kg of phenols to 1 tonne of refuse.
7.3.8 Plastics, Polythene
7.3.8.1 Background
As a consequence of the plastics era, there are a variety of plastics in our midst and the environment is heavily loaded with them. Of particular concern is polyethylene (polythene) and its use as carrier bags - "Kaveera". This use is widespread throughout the country and is rampant in both rural and urban settlements. The use of kaveera far out-strips the use of all other plastics. The concern is over injudicious disposal onto soil.
Polythene is the same material often also called Polyethylene and locally called "Kaveera" in Uganda. It is a material made from a simple chemical called ethylene which in turn is obtained from distillation of petroleum. The manufacture of polyethylene from ethylene is done using a chemical
reaction called polymerisation. (Polymerisation is the joining together of many small molecules (monomers) to make very large molecules (polymers).Urethane Polyurethane Cushions, mattresses
7.3.8.2 Polyethylene Production in Uganda
The production of polythene bags in Uganda stands at about 700 tonnes annually from 13 different manufactures. The local production accounts for only 10-20% of local consumption. The rest of consumption is supplied through other countries. The level of importation is uncertain but some sources suggest 40,000 tonnes annually.
7.3.8.3 Environmental impact: Damage of Soil
All plastics are hazardous materials from the time they become wastes. This is a direct result of their physical properties, namely, that they are not degradable through the natural processes. As regards soil, the main impact arises when polyethylene ends up in the soil and it does not rot. The bacteria that are responsible for the rotting process of natural materials are not able to decompose polyethylene.
The chemistry of natural processes is equally weak to degrade polyethylene. The material is stable to water, non oxidizing acids and alkalis and therefore, natural acidity does not affect it. It is also non-permeable to water. When buried in the soil it thus, creates a micro-desert and plants in its vicinity experience moisture stress. Polythene therefore, enhances, soil degradation; because partly, polyethylene remains stable in the soil almost indefinitely.It is emphasised that the waste disposal system in the country is inadequate. Waste disposal is inadequate in urban centres and it is virtually non-existent in rural areas. Consequently polyethylene is slowly but surely contributing to degradation Uganda's soils.
Furthermore, it must be emphasised that Uganda's economy is based on agriculture which in turn depends on good soil. Fertile soil is therefore, the most basic economic asset of Uganda. The soil should be jealously guarded. Polyethylene is attacking this important economic asset. This type of soil degradation is already observable in suburbs of Kampala, Masaka, Mukono, Jinja, Mbale. These are corresponding to the heaviest monitorable use of polyethylene bags. The same can be said of any trading centre in the rural areas.
When polyethylene gets distributed into the soil as described above, there is no foreseeable technology or way of rendering it harmles. Prevention is the only action available.
7.3.8.4 The Objective
To put into place adequate preventive measures through good waste management practices.
7.3.8.5 Strategy
Increase public awareness and change public attitudes on use.
Improve garbage collection with particular interest on polyethylene for destruction.
Impose a controlled ban on the disposal of the material onto the soil.7.3.8.6 Actions
Require the users to collect and incinerate all used kaveera; the incineration should be done out-doors in the open and at least a distance of 50 metres from the houses;
Prohibit the dumping of kaveera on land other than an authorised land-fill;
Require the manufactures and suppliers to inform the users on safe disposal of kaveera.
Assign the responsibility of ensuring compliance to the Chiefs (or Local Authorities) at rural level and to the urban authorities in towns.
Encourage the manufacture and use of biodegradable materials, and where plastics must be used, encourage the use of biodegradable plastics and/or recycleable plastics in place of the common kaveera.