Integrated management: the art of doing two things at once

If the handling of exhausts and effluents are looked at simultaneously, and combined with the opportunities for recycling and recovery, not only will a manufacturing process be more environmentally responsible, it can also be made more profitable.

The discharge tower was hardly noticeable at De Montford University (white piping under the eaves)

The discharge tower was hardly noticeable at De Montford University (white piping under the eaves)

Designing a plant with space as well as function in mind can reduce its footprint and increase its aesthetic value
The final aim of any waste treatment strategy is to find the most cost-effective technology for discharging the minimum volume of waste into the environment. All too often the subject of waste treatment, which includes air pollution, is handled piecemeal, whereas taking an overall, integrated approach is much more efficient financially and effective technically.

Minimising emissions
There are five distinct areas that can be defined within an integrated waste treatment strategy:

i. minimisation of waste produced,
ii. gas abatement,
iii. liquid effluent
treatment,
iv. chemical recovery,
v. final disposal.

The need to minimise waste in the first place may seem self evident, but IEM Technologies Ltd was recently asked to look at the treatment of an exhaust stream with a very high SO2 content resulting from H2S incineration.

Simply asking the question, 'Can emissions be decreased by reducing the levels of H2S being sent into the system?' lead to an internal audit of usage that may cause an improvement in output levels. Though this is quite a dramatic example, it is not an isolated case.

Waste gas abatement
Abatement of industrial waste gases employs various technologies, one of the most commonly used is wet scrubbing, particularly where the exhaust stream is toxic.

At its simplest, this will be a water system, though water alone is unlikely to provide adequate removal levels. IEM Technologies has been a specialist provider of chemical scrubbing systems for use by compound semiconductor fabricators for over a decade. The waste streams from these fabricators contain high levels of arsine and phosphine and are some of the most technically challenging to be found in any industry.

In IEM Technologies' experience, the key to the effective use of scrubbing technology is the careful design of the scrubbing regime and the accurate and precise control of its delivery. Continuous, computer aided monitoring of key operating parameters ensures that removal levels are maximised and that the cost of the scrubbing chemicals is minimised.

Continuous monitoring also provides advance indication of impending maintenance issues, which reduces unplanned downtime and aids planned maintenance programmes. Remote monitoring is possible with IEM Technologies' systems using an Ethernet connection, which is invaluable in fault diagnosis.

Liquid effluent may be produced directly from the industrial process itself or as a by-product of toxic gas abatement. But whatever its origin, the aim is always the same - to remove the toxic content and to discharge clean air and water with the minimum volume of waste needing to be disposed of and the maximum sent for chemical recovery and recycling.

Water is perhaps the most obvious candidate for recycling, either within the process itself or in a symbiotic relationship with another activity. IEM Technologies is currently advising on a water treatment system in India in which water from the treatment of animal slurry is used for irrigation.

This is part of a larger system providing potable water from a bore hole. In Taiwan, where water is a much scarcer resource than in the UK, the level of water recovery has been crucial in IEM Technologies winning a number of contracts to install toxic gas abatement systems at semiconductor wafer fabrication plants.

Economic implications
In an ideal world, the best waste treatment solution would be one that removes all contaminants but in the real world, the best solution will always balance environmental responsibility with what is commercially acceptable. An overall approach to costs is imperative. Initial outlay must be considered alongside running costs, and cheapest is not always best. Reliability is the result of both good initial build quality and commissioning and a well implemented maintenance programme and saves one of the biggest costs of all: that of system failure and consequential production downtime.

It is easy to overlook the value of investment in initial plant commissioning in ensuring that the treatment system is operating at optimum performance. IEM Technologies is currently advising on improvements to the acid removal system at a plating plant.
Initially upgrading the system was under discussion but as soon as on-site inspections started, it became evident that the scrubbing system had not been properly commissioned, and together with other problems, the scrubbing tower packing was inadequate. This, unsurprisingly, has resulted in the plant not operating very effectively and running costs being higher than necessary.

Costs take many forms, some of which are not numerical. Public image and profile may be difficult to put a price on but can be of major importance. Public appearance was certainly imperative at De Montford University in Leicestershire.

A gas removal system was needed by the electronics department but on a building of architectural importance. Discharge stacks are not noted for their beauty but IEM Technologies' design team was able to design and build an aesthetically acceptable stack that met local planning restrictions.


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