Monday, July 16, 2012

HEAVY METAL POLLUTION OF WATER RESOURCES - CAUSES AND IMPACTS


The term “heavy metal” is not altogether clearly defined, but in the case of water pollution, these are metals such as arsenic, cadmium, iron, cobalt, chromium, copper, manganese, mercury, molybdenum, nickel, lead, selenium, vanadium and zinc. While heavy metals do tend to have a high atomic mass, and so are heavy in that sense, toxicity seems to be a further defining factor as to what constitutes a heavy metal and what does not.

Municipal treatment plants are generally ill-equipped 
to cope with significant heavy metal pollution, both 
in terms of removal and safe sludge disposal.
Heavy metals occur in the earth’s geological structures, and can therefore enter water resources through natural processes. For example, heavy rains or flowing water can leach heavy metals out of geological formations. Such processes are exacerbated when this geology is disturbed by economic activities such as mining. These processes expose the mined-out area to water and air, and can lead to consequences such as acid mine drainage (AMD). The low pH conditions associated with AMD mobilise heavy metals, including radionuclides where these are present.  Mineral processing operations can also generate significant heavy metal pollution, both from direct extraction processes (which typically entail size reduction - greatly increasing the surface area for mass transfer - and generate effluents) as well as through leaching from ore and tailings stockpiles.

While mining activity poses significant risks for heavy metal pollution, this sector is not the only culprit in the industrial sector. Many industrial processes can generate heavy metal pollution, and in a large number of ways. Clearly, some industries will be more likely to pollute than others. Hence the electroplating industry, which can produce large volumes of metal-rich effluents, will naturally be a more likely polluter than the food processing industry, for example. This is not to say that players in this industry will necessarily pollute, and it is in fact in the electroplating industry’s best economic interests to minimise metal discharges, since these are inversely proportional to resource efficiency. Reducing losses by minimising drag-out from plating baths leads to reduced metal discharges, for example. The lead-acid battery manufacturing industry is another example of an industry which can generate metal-rich effluents as well as airborne lead pollution which can subsequently be deposited in surface water resources (and of course on land). So clearly, where an industry uses heavy metals as key input materials, pollution risks increase.
  
An example of a large non-point source of heavy metal pollution is coal-fired power generation, which can contaminate water resources through aerial deposition of mercury emitted from boiler flues. Technologies such as wet scrubbing are available to remove much of this mercury, but of course the effluents produced have to be safely handled to prevent subsequent pollution. Some of these processes have the primary goal of removing sulphur dioxide, with heavy metal removal a welcome by-product of the scrubbing process. The industry also generates large amounts of ash which itself contains heavy metals, including uranium. 

The importance of minimising heavy metal pollution for industrial organisations extends beyond simple compliance. The impacts of heavy metal pollution on living organisms are very serious. Heavy metals are bio-accumulative, toxic at high concentrations, have neurological impacts, and some are carcinogenic. They can also interfere with chemical processes by poisoning chemical catalysts and can impact on biochemical processes by interfering with enzyme action. There are hence serious environmental, economic and social impacts associated with heavy metal pollution. 

As always, a detailed risk assessment, which must include include quantitative measurement, is recommended to help you to understand your heavy metal pollution baseline. Where problems are identified, the solutions you choose should focus on the source of the pollution as far as possible, in line with Cleaner Production principles. End-of-pipe treatment methods are unavoidable in many circumstances, but where they are employed, care should be taken to dispose of resultant concentrated metal wastes safely. For example, lime treatments, which raise pH and precipitate metals, produce concentrated wastes (sludge) requiring safe disposal, as do processes such as reverse osmosis (retentate). Take care then that you are not just moving the problem around through poor management of these wastes, which generally require disposal at certified hazardous waste installations.

Friday, July 13, 2012

PRACTICAL ELECTRICAL ENERGY CONSERVATION ON INDUSTRIAL SITES: ARTICLE 2 - INDUCTION MOTORS

Induction motors are the heart and soul of most industrial sites. As modern motors have become more and more efficient, opportunities have arisen to replace older motors with newer ones, thereby harvesting the energy benefits. This replacement, while guaranteed to save energy and possibly reduce maximum demand (for sites that do not have PF correction) is not necessarily always financially viable, and you will need to take some care in investigating opportunities in this area.


Motors driving dosing pumps at a water treatment works
The power factor and efficiency characteristics quoted for induction motors are based on full-load conditions i.e. conditions at which the power delivered by the motor at the shaft is equivalent to the rated capacity of that motor. Motors operated at part-load will have a reduced power factor and efficiency. Don’t therefore make the mistake of simply looking at power factor and efficiency characteristics of two motors for comparison when looking at replacement options. You will need to do field measurements to determine power consumption and ascertain loading, which will then provide additional input to the decision, which may even be that you need to install a smaller motor. An under-loaded energy-efficient motor will not achieve its full load efficiency, and savings may therefore be less than expected. It is also important to assess transient conditions, such as start-up, when power draw can be much higher than during stable running, and variations in power draw which result from the nature of the process being driven by the motor. Whatever motor you install would need to cope with those conditions. 

Aside from the technological issues associated with the motors themselves, there are other system-related issues which are in many cases much more important. Probably the first question I want answered when looking at motor replacement is: “what are the annual running hours of the motor?” Remember that in energy terms, we are looking here at kWh, and while efficiency reduces kW, if the hours (h) of running are small, the total energy savings from retrofitting will also be small. Low-efficiency motors that run continuously in plants that run around the clock are therefore always attractive retrofit candidates, while a motor that runs intermittently in a dayshift-only operation will probably not be interesting, unless it is so under-loaded that its efficiency is only a fraction of full-load efficiency.  In this latter instance, you may even want to install a smaller standard-efficiency motor that is being replaced elsewhere to limit costs while still saving electrical energy.

The next system-related issue to consider in terms of motors are the drive systems associated with each motor. These entail things such as gearboxes, chains, belts, couplings and shafts. You need to consider not only the technological issues here (for example, cogged belts are reported to use 2% less energy than standard v-belts without any changes required to pulley systems) but also the maintenance issues. Key maintenance issues from an energy efficiency perspective could include:
  • ·         Lubrication of bearings, chains and gearboxes;
  • ·         Alignment of shafts, couplings, sprockets and pulleys;
  • ·         Tension levels in belts and chains

It is important to include checks of these types of issues as tasks in your preventive maintenance programme.

The final system-related issue is that of the process being driven by the motor. An efficient motor driving an inefficient process still constitutes an inefficient operation. Hence ask yourself if that agitator is of an efficient design, if the pressure drop in that pumping system as low as it could be or if that fan design is best for the application, as examples. Delve deep into your processes and look at the constraints around your plant, remembering that the overall process only has the capacity of the constraint. It makes no sense to run non-constraining processes at higher throughputs than the constraint, leading to unnecessary circulation, waiting times (with motors running in many cases) or higher flow rates than needed in the case of pumped systems (remember that when pumping fluids, pressure drop varies with the square of flow rate). These types of issues are unique to each individual industrial site, require comprehensive process knowledge, and in my experience are the most neglected when it comes to energy efficiency programmes and projects. They should in fact be addressed first, with motor replacement options only investigated once underlying processes have been optimised.

Wednesday, July 11, 2012

UNDERSTANDING THE STEPS IN THE PROBLEM SOLVING PROCESS


Want to boost your performance? Embed formal
problem solving into your organisation at all levels.
Then sit back and watch performance take off! 
I touched on problem solving as an essential skill within sustainable organisations in an earlier post, and will now share with you the details of the individual steps required when formally solving problems. What follows largely applies to the industrial environment, but the principles really apply anywhere. It would be useful to review these steps in conjunction with the diagram in my previous post on the subject.

There are many root cause analysis and problem solving techniques available, but what I find is that in rushing to use these, we often lose sight of the fundamental process of problem solving. If you use what follows in a disciplined manner, you will find that the process of problem solving becomes simpler, and that achievement of concrete results is facilitated.

The individual steps that I consider essential and their relevance are outlined in detail below. Each of these can be significantly expanded upon – I may do this in future posts if there are specific questions regarding them, but there is sufficient information below for you to make a start.

Problem Detection
An undetected problem will forever remain an unsolved problem, and it is vital that problems are detected promptly. The speed with which problems are detected is often a function of how well-organised the performance-monitoring apparatus of an organisation is functioning.
Given that problems are essentially gaps between desired and actual performance, systems should be in place to track key performance indicators for all processes considered to be important. The nature of these systems and the frequency with which they are used is largely determined by the type of process being monitored. An issue such as staff turnover will have a very different type of system to one which monitors manufacturing costs, for example.

Assessment of Problem Complexity
At this stage of the PS process, we are interested in confirming that the problem does indeed exist (e.g. are there measurement issues?), and also in gathering important preliminary information that will allow us to frame the problem accurately. Examples of the types of questions we would ask at this stage would be:
  •  When does this problem occur?
  • How big is the gap between desired and actual performance?
  • Which specific products are affected?
  • Has this problem happened before?
  • What has changed?
  • Etc?



Compilation of the Problem Statement
With the information above in hand, we are now able to succinctly state what the precise problem is that we intend to solve. This is a vital step in the PS process, since it sets the scene for the entire problem solving event. Problem statements should:
  • Use clear and simple language;
  • Contain specific facts;
  • Be short and to the point;
  • Refer to the problem only, NOT solutions;
  • Focus on one specific problem.


Lack of attention to detail here can misdirect the process, increase the time from detection to solution and cost money, so it is always worthwhile to invest time in getting this right.

Identification of Potential Causes
Every problem can always have more than one potential cause, and this step is about using the information at hand to identify all potential causes of the problem. Techniques such as brainstorming, mind-mapping, Cause-and-Effects Analysis and Why-Why networks are just some of the many available tools one could use to identify potential causes. This step of the process relies very heavily on the business/technical skills of those solving the problem (so-called “subject-matter expertise”). Knowledge of problem solving techniques means little in the absence of the technical knowledge relevant to the specific problem at hand.

Determination of the Root Cause of the Problem
The root cause of the problem will lie among the potential causes identified and its identification relies heavily on the gathering of irrefutable evidence, gathered at the site of the problem as well as upstream and downstream of the problem location.

Revision of the Problem Statement based on Identified Root Cause
In much the same way as the original Problem Statement guided the identification of the root cause of the problem, revision of the Problem Statement after identification of the root cause guides the development of solutions to the problem. This is best illustrated through an example:


Problem detected
Bearing failures on mixing vessel causing
excessive downtime

Original Problem statement
Mixing vessel bearings fail every 3 months
Identified Root cause
Dust from powders being mixed entering bearings
Revised problem statement
Dust entering the mixing vessel bearings is causing premature failure



It is clear from the above how a revision of the problem statement focuses the solution development process on eliminating the dust problem. This is a more detailed account of the problem that has to be solved. Premature bearing failures could come about due to manufacturing defects, a lack of lubrication, use of the incorrect lubricants, operation of the mixers outside of design parameters and other reasons. All of these would have been eliminated during the identification of the root cause of the problem, and can now be discarded in developing appropriate solutions.

Identification of Potential Solutions
Solutions may encompass technology, work practices, management systems, engagement with stakeholders (e.g. alternative suppliers) and changes in materials, to name a few examples. An individual solution may incorporate a number of these issues. It is therefore important to keep an open mind in the determination of the various possible solutions to a particular problem. Once these solutions have been identified, the best one can be chosen.

Selection of the Best Solution
Selection of the most appropriate solution is carried out by specifying the criteria that solutions need to satisfy, and then scoring each individual solution against those criteria. Some criteria can be non-negotiable (i.e. if a solution does not meet it, that solution cannot be accepted) while others may be scored on a defined scale e.g. 1= poor, 2 = acceptable, 3 = excellent. The criteria can be assigned weights, and the final score would then reflect which solution scores highest AND meets all non-negotiable criteria.

Typical criteria could include:
·         Cost of the solution;
·         Robustness;
·         Time to implement;
·         Availability of local support;
·         Etc.

The selection of a solution is ultimately a judgement process, and despite this attempt to better quantify the benefits of individual solutions, ultimately there will intangibles that would need to be factored into the final decision. These apply particularly where two solutions score very closely.

Planning and Implementation of Solutions
Depending on the scale of the solution, these activities can range from changing the set point of an automated process to a full-scale engineering project. It is important to remember that no matter how simple or complicated a solution is, its success will always depend on the people who operate and maintain it. During planning and solution implementation, involve all affected stakeholders, many of whom will already have been involved during the problem solving process.

Ensure also that, since in implementing a solution you are introducing a change, the relevant change control interventions (involves systems) and change management activities (involves people) are in place. This again depends on the scope of the solution, and could include:
  • Updating of documentation such as engineering drawings, work instructions and        maintenance schedules;
  • Purchasing of necessary spares;
  •  Training of affected staff;
  • Performance monitoring systems;
  • Updates to budgets.


The idea is to ensure that once implemented, the solution is seamlessly integrated into your operations.

Evaluation of Solution Effectiveness
An effective solution:
  •  Addresses the root cause of the problem, preventing its recurrence;
  • Does not introduce unintended consequences;
  • Meets the criteria upon which its selection was based once it is put into operation.


A solution may need to be in operation for a period of time before its effectiveness can be evaluated, particularly with respect to unintended consequences.

Where solutions are shown to be effective, the problem solving process is complete. Where a solution is not effective, additional problem solving may be necessary. The reasons behind the lack of effectiveness will have to be determined by revisiting specific aspects of the PS process, as indicated in the flow diagram in my original post.

Summary
In summary then, do not allow yourself to become enamoured by the plethora of problem solving tools and techniques available without giving due consideration to the over-arching process within which these tools are to be deployed. Spend sufficient time defining the problem upfront – this is the foundation for the efforts that follow. Ensure that the skills of the team are appropriate in terms of the subject matter expertise required. Problem solving techniques without this knowledge can only get you part of the way - you need deep business knowledge as well. Once the root cause of the problem has been determined, re-focus the process by revising your original problem statement. Develop as many solutions as possible; you can never have too many potential solutions. Choose a solution based on a detailed comparative analysis, and where two solutions are close in terms of their score, use your professional judgement to separate them. Plan and implement solutions with people in mind, and always conduct a formal evaluation of the implemented solution once sufficient time has elapsed. Revisit the problem solving process when implemented solutions are not effective, and repeat necessary steps in this process until an effective solution has been implemented. This last step is in line with the PDCA cycle, and does not represent failure, but is a normal part of the PS process.