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MALCOLM M. RENFREW University 01 Idaho Moscow, Idaho 83843
Waste Disposal in Teaching Laboratories Martin J. PHt, Plant Manager Safeway Sludge Disposal Ltd., Bannerly Road, Birmingham833, England
The term 'waste' has two unfortunate connotations. Firstly it is often equated with trash, that is, material of no value and thus not worth considering. Secondly, the production of waste is sometimes considered
immoral, and therefore something we will pretend does not happen in our place of work. In this article I would like to show that a sensible and positive attitude toward waste can both aid the safe, smooth running of a teaching laboratory and also be an important learning tool. Teaching laboratories have important differences from those used for testing or research. The major difference is that the laboratory workers are by definition mostly inexperienced in their tasks. Counter to this disadvantage is that matters such as the amounts and types of waste arishg are predictable and basically capable of being controlled. The main control aspects are: design of experiments, organization of work, and supervision. I t is essential to remember that in the teaching situation, it is always possible to delete an experiment which raises safety problems. Devising a replacement is often easier than trying tomake adiffieult experiment .~safe. On the other hand. a "prize evrry time" lahorntury in which nothing ever gorswrong is not the ideal teaching environment. As long as there is no major danger, then, coping with spills, getting sticky failures out of flasks, and similar oroblems are excellent trainin~forthe real w&d. Making students think about waste disposal, and realizing the consequences of their actions, is a useful step in producing effective and socially responsible scientists, engineers, and citizens. ~
Martin J. Pitt gained Graduate status from the Royal Institute of Chemistry by examination in 1973, fallawine~.nart-time studies at Warlev Cdlegr of Technulugy He hecame a ('harterrd Chemivt in 1976. Thir year he h a brrn swarded an M.Phil for a part-time course of research in the Dept of Chemical Engineering, University of Aston. Birmingham, U.K. The greatest part of his working life has been spent as a laboratory teehnician, and he was latterly Laboratories Superintendent in the Department of Chemical Engineering, Aston University. He returned to industry as a Development Chemist for Croda Synthetic Chemicals in 1978, and he has recently moved to Safeway Sludge Disposal Ltd as Plant Manager for their new Waste Chemical Treatment Plant in Birmingham, U.K. He is co-inventor of a system for the rapid identification of chemical hazards of unidentified substances, eurrently being test marketed in the U.K. under the name 'Hazkit'.
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Psychology and Waste Disposal As all exoerienced teachers and manaeers know, people learn in many ways apart from the lecture and the texthook. It ir en unfortunate fact that lormol teaching on rafrts is often contradicted by unconscious teaching by example in the same place. If a student sees some professor in shirt-sleeves, with a pipe in his mouth, stroll into the room and Dour benzene down the sink. then that stuhent is unlikelv to he imoressed hvstern notires and liits of ruler. Thus it is impawtant to make sure that technicians, staff, xraduate students, etc. a n in a conscientious fmhion when dealing with waste. Though in other circumstances a skilled technician (far eaample) might properly use another technique, he or she should follow the class rules when in the classroom. This also applies to ~
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research workers who may be visible in the next room, or who may use some communal equipment. In cases of particular difficulty, it may be politic to arrange for some individual to be elsewhere during classes. The situation to aim for is a simple set of rules whieh the student can understand and appreciate. Even more critical, these rules should be seen to he obeyed, and to be thought important by the people around the student. If the room starts off clean and tidy, the student is more likely to work in a clean and tidy fashion. Breakages and spills should not be occasions for fits of shouting, but allow the technicians and supervisors to demonstrate their skill in coping with matters outside the book of instructions. The foregoing deals with the way students, like all primates, learn by imitating their elders. However, they also pick upan amazing amount of misinformation during the educational process, whieh they can apply in all goad faith when hard facts are in short supply. In my years as a laboratory technician, I was endlessly surprised by the new ways which creative young minds could devise ta wreck equipment. This was rarely through mischief or stupidity, more usually the cause was the wrong impression they hadgot during some perfectly laudable lesson. As an example, consider volumetric analysis. The acid1 base neutralization is one of the fundamental pieces of practical chemistry all over the world. By definition, the solution a t the end is neutral. In the early days of teaching it will not even he mildly toxic, and it is perfectly proper to dispose of it down the sink. So far, so good, but deep in the caverns of the student's subconscious a concept takes shape. It can he expressed in the equation
used = neutralized = safe = pour down sink Years later, the student will associate "waste disposal" with same rather dull Lectures on ecology, and will happily tip anything from mercury to ether down the nearest sink. A combination of foresight. organization and downright low cunning will then he required by anyone wishing both to protect the lahoratory and to alter the student's ingrained behavior.
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Organization Anyone setting up, or re-evaluating, a teaching laboratory should consider all waste, not just the obviously toxic one. Burning waste paper can destroy a laboratory as effectively as a chemical explosion, and broken glass can injure as badly as corrosive agents. Some laboratories make do with a large bin for solids and a can for liquids, but such an arrangement is rarely satisfactory. A better minimum segregation would he: (1) paper and inert solids (2) chemically contaminated paper and some chemicals (3) broken glass (4) halogenated solvents (5) other solvents. Other categories of waste will depend on the nature of the laboratory. A special sack may be required for biological material. Special bmes are available for used hypodermic syringes. A screw-capped plastic jar may be kept for broken thermometers. Disposable clothing may be collected. A particular solvent which is extensively used may be collected separately for recovery. Especially difficult materials may he placed in a suitable closed container for later treatment by a techni-
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It may well be that some wastepwillrventually be disposed c,f tclgether. For example. the DaDW and broken glass will likely cn into nortiai refuse. ~ o w e k .r seereeatiokk . .. .. the laboratory is still important for a variety of rmsons: the decision to comhrnr wastes should he made by an experienced person at Irisure, and not an inexperienced student in the rush to finish class on time! In smwarens, DaDQr bins are emptied by umkilled lnhor. ;iho have been known & suffer cuts and burns from glass and chemicals. Personally, I prefer to have all laboratory waste dealt with by technicians, leaving the cleaners to collect from offices, etc. Sometimes salvage of glassware, particularly that with ground glass joints, is possible. Such items are clearly visible in a glass-only bin, as are broken thermometers. My own investigation following fmding a thermometer stem in the bin has more than once disclosed a p w l of mercury somewhere. A segregated "waste" solvent from one process ean sometimes be used for a less critical purpose (such as cleaning)-hut not if it is in a can with a hundred unknowns. The location and the amount of waste receptacles needs some thought. Clearly they should not interfere with gangways, fire ertinguishers, etc. No one should have to leave the r w m to d i s w e of wastp-the temptation to 'lose' it is too great. Conversely, outsiders (such as research workers) should be heavily discouraged from bringing wastes into a teaching laboratory. A special waste container for a single experiment or piece of apparatus is oftenuseful: normally an appropriately sized bottle will do. If need be, the technician can add this to some central store. Precious metals can be accumulated in this way. S p e d poisons can also be kept apart by this means, rather than risking their getting into routine waste. Clearlv. -~~~~~ .. waste containers should be of such a size (and regularly emptied) so that there is nudanger of their henming full during the course of n class. Having said that, it is pref~
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erable to have small containers emptied frequently rather than enormous 'once a year' units. This is for the simple reason that if there is a fire or spillage, the less material involved the better. If solvents are accumulated in 5- or 10-gallon drums for recovery or disposal, then the drums should be in a suitable safe area away from the laboratories. Containers no greater than 5 l should he available in the teaching laboratory, and transfer should be w r i e d out by trustworthy staff. Furthermore, the academic staff in charge of a class should check that waste receptacles are in order before starting the class. AU waste containers should be clearly and adequately labelled. The labelling and, if needs he, the container should he replaced as often as necessary. Naturally, waste containers have to be of adequate construction. They should also be ergonomically satisfactory. Plastic pedalopening hins are suitable for many types of solid waste. They are chemically resistant, easy to clean, and can be color-coded. They are preferable to open bins because items can neither fall in accidentally nor be aimed in from a distance. Bins with a loose lid generally prove inconvenient for frequent use. For the collection of solvent- or chemieal-soaked paper etc., a stainless steel pedal bin with a plastic liner has some advantage. If a fire. should start it will probably be contained by the metal body of the bin, and will often he snuffed out by the exclusion of oxygen. Special hins with fusible links or other fire protection design features are available, though they are mainly intended for industrial use. Incidentally, if a bin is used to collect chemical solids, it is best to provide a supply of plastic bags and sealing ties so that the chemicals are collected in small packets, instead of heing mixed together. Solvent waste can he collected in glass bottles or metal cans. The ideal is probably the specially-designed stainless steel cans which are commerciallv available. Thev are very expensive. hut they last! Ordinary tinh e d cans may he nrrrptahle, but they are prune t u currmion at the seamr by acid or caustic traces in solvents. Even traces of wacrr in chlorinated advents can cause such corrosion. The effects can hr mitigated by ensuring that tracer of acid chlorides, acetic acid, e&. are neutralized before discarding the solvent, hut in any ease it is safest to discard the cans every few weeks. Glass bottles are relatively free of corrosion problems, but do tend to break. Some manufacturers are now providing bottles covered with a special film which holds the pieces together long enough to deal with an accidental breakage. An alternative is to'keep the battle in a suitable container such as a plastic winchester carrier. Bath the bottle and the outer eontainer must be clearly labelled. For safe working, the solvent waste container should he kept in a tray at hench height during the class. The tray would preferably be under a fume hood, though this depends on the materials used. In any case, it should he in s well-ventilated area as well screened or distant from work areas as is practicable. Ohviously the solvent waste should he kept away from sources of heat and experimental areas, but a spillage could make a nasty mess of someone's bwk in a wits-up area. Outside class hours, it is best if the container is emptied or put away in a suitable solvent euphasrd, or both.
Special holders for plastic sacks are particularly useful for biological material, but also find applicatiun for collecting disposable clothing or paper towels. Normally a sink or washhasin will be provided in the laboratory or an adjacent room for hand washing. It is best if a sink can be reserved for this purpose alone. A soap dispenser and a paper towel dispenser should be provided, and a bin which is only used for the towels.
srudent s.lraning up ran I,r pnmoted bv vnriuua nmbinations of I hrtats and l~riorrv. but should n~ r r r m d to puttin&m m i u u , ~ y . Putting apparatus and chemicals away is a chore for the technical staff, hut it gives them the chance t o examine items-to look for cracks on glassware, dirty marks, or other faults. In all laboratories students should be encouraged t o report breakages a t once, even the most minor ehipon the edge of a beaker. Discarding cracked glassware should be seen as a positive contribution to safety, rather than an attack on the budget. A suitahle corner for salvageable items is a good idea, but repairs should be carefully controlled, and limited by the skills and equipment available. If s full elass-blawineservice is a t hand. ~.then eroeLadvice sh&d be taken. Le\s well-endowed tnititutiuna haw, houever, hem k n w n toattempt repairs heycmd the capabilities of the staff. Poorly repaired glass may appear perfectly good, but can crack in use-with ohvious dangers. It is certainly not worth such a risk to save a dollar or two on routine glassware. The rule for students, technicians, and academic staff must be: "If in doubt, throw it out"whatever the grumbles of the accountants. For very expensive items, it is of course worth paying an outside expert t o repair them. Most laboratories come to some regular arrangement with a local firm known to be reliable. A common attempt a t economy is the purchase of chemicals in large containers. However, savings from bulk buying are often lost by the usage of these containers, and there can he safety problems. Firstly, if a large container gets broken or spilt, the financial loss and the hazards are greater. Secondly, it is easier to lose control when ~~
Positive Thinking In a n ecologically-conscious society, there is no reason why waste disposal and cleaning UD cannot he considered s Dart of the exoer-
ensures some rudimentary attempt a t cleaning, which can be improved by a little explanation of techniques, and possibly a demonstration or two. If available, a radiochemistry laboratory provides a wonderful o~oortunitvto demonstrate the real meanine
apparatus are magically restored overnight by elf-like technicians. In the latter case,
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taking material from a large container. A small person may well have difficulty in pouring from a 2%-1 bottle of (say) a r b o n tetrachloride or fuming sulfuric acid, particularly when wearing oversize PVC gloves.
Thirdly, the sight of a vast aspirator with gallons of acetone, say, tends to encourage students to be profligate in their use for rinsing-half a pint may he vaguely swirled round a flask before being instantly poured down the sink.
'There are other more tcehnirnl problems. Some chem~rnlihave only n lmned shelt-life, nnd any P X C W nt thp pnd uf tine academic year may not be suitable for use in the next one. Many more are sensitive t o moisture or air, and it is a fact of life that students can be exuected to leave cam loose or off altosether. Who has not seen &dents strugglingwith a sticky mess in the bottom fifth of a large jar of PsOs?
The simple answer is to consider each case on its merits, but ensure that the containers used by the students are appropriate to the experiment. The bench containers can he filled from larger ones as a part of naimal class preparation. With especially difficult materials, I have found it expedient on oecasion to supply only a little more than is re(Continued on page A264)
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periment uses a fresh one, or by having a larger amount put into a series of sealed containers by a skilled person using a glove box. In other cases the amo~intcan be based on a week's supply, or three experiments, or whatever.
Manufacturers now supply many cbemicals ready made up as reagents-notably as solutions for volumetric analvsis. I have tomd the small extm wst usually u,orthu,hile fur msns teaching lnl,cmtory purpose8 I ' n fmunately, not all techn~cinnrcan be relied upon to produce an accurate solution from the raw materials. Those that can he relied upon are probably hetter employed making up non-standard reagents! ~
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I do not wish to suggest that students should have everything ready and pre-measured. On the contrary, correct measurement techniques are vital, and should he taught under the best possible conditions. Any problems should as far as possible he those which are intended, such as esleulation of stoichiometrv. and not the haohazard result
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set in the experimental instructions. Students can be asked to discuss in tutorials their laboratory syntheses as industrial processes. Which materials would be most hazardous to chemical plant workers? How would the laboratory disposal method have t o be modified to meet anti-pollution legislation? Would recycling he possible?
Given reasonable preparation time, the elean-up and waste disposal aspects of experiments can provide opportunities for the guided self-discovery processes favored by m a w educationalists. Simole but fundamental chemical eanceots mav be shown in actual use. A few example*: Washing m m i r cihle solventr with aqueoui NnrVO,, hvdn,lysi~uI'activ~groupi with NaOH; dduting strong acids (correct technique) before neutralization; oxidation of reducing poisons such as oxalates or sulfides; dissolving some solids for disposal as liquid waste; collection of mercury for recovery; adding inhibitors t o ether or monomers.
Spillages need to he carefully considered before they occur. The person responsible for a teaching laboratory really ought to ask himself'what action should be taken if all this was spilt?' far each substance used in the class. The more difficult the answer, the better the reason far keeping the amount as small as possible. Not only does the hardware
need t o be available, the action to be taken must he agreed upon in advance. The students must be told to stop the experiment a t once and report the situation. Supervisors, demonstrators, and technicians need to know their roles when this happens. The instruction might range from the student being told to wipe it up himself, perhaps, to stand back and let a technician deal with it, right up t o immediate evacuation of the area. Whatevir the case, there are few things more emharrassing than contradictory orders from those in charge of the class! If possible, the cause and the method of treating spills should be discussed with the student or students shortly afterwards, since it is a lesson that might well be remembered.
Conclusion Waste disposal is s vital part of management of all laboratories. Teaching laboratories have particular problems and give a special duty to look after the safety of experimenters. A positive and thoughtful attitude towards waste is to be encouraged amongst students. This way, we may produce scientists who are adequately responsible for the safety of their eo-worken, and industrialists who will adequately care for the environment.
