Integrated management: the art of doing two things at once

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.