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Towards achieving Zero Liquid Discharge in process industry

Prior, Alison D. (2008) Towards achieving Zero Liquid Discharge in process industry. Honours thesis, Murdoch University.

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Fresh water is invaluable in supporting life on Earth. It is scarce, cheap, and exploited. A number of initiatives have been taken to reduce the consumption of fresh water, particularly in agricultural and residential situations. In industry, much focus has been placed on pollution control and wastewater minimisation, however attention to source protection and water minimisation is nominal. The ultimate goal of any water management program is achieving Zero Liquid Discharge (ZLD). This research argues that with a current focus on pollution control and wastewater minimisation, ZLD is not attainable. Protection of water sources has recently been identified as the most critical issue preventing sustainability of industrial water management. It is also given the least attention. This thesis argues that incorporating water auditing and water conservation programs into industrial water management programs is a crucial step towards achieving water source protection and ultimately in achieving zero liquid discharge. A water audit of key water using operations at the BP Refinery in Kwinana has been undertaken to test this hypothesis.

The BP Oil Refinery in Kwinana is an example of an industry which has received much attention for its
excellent practice in water management. BP has almost halved its total water consumption from 7ML/day in 1996 to 4ML/day in 2007. It has developed employee awareness-raising programs, on-site recycling and reuse of wastewater and is now in the final stages of using recycled domestic wastewater as a key water source, expected to minimise fresh water consumption even further.

Despite this, detailed analysis of the major water uses at the refinery show a number of poor management
practices and severe wastages of water. In assessing the whole of refinery water use in Chapter 2, we see that poor record keeping and meter reading is commonplace. Major leaks are left unattended and information about major water-loss incidents is often unavailable. In Chapters 3-5 we look more closely at specific water using operations within the refinery. The refinery steam system is one of the largest fresh water users on site and has been commended for its steam trap survey program and the development of condensate return infrastructure, increasing the percentage of condensate returned from 32% in 1998 to a condensate return target of 50% in 2007. Despite this, major losses still occur in the steam system and turnaround time for fixing major leaks can take years. Simple measures can improve the condensate return rate from 50%-75% quite easily, but there are few incentives for the refinery to invest in such a program which offers diminishing returns. The use of water in process units is enormous, particularly the use of scheme water in the Residue Cracking Unit. A number of available tools and techniques, particularly water pinch and water optimisation tools, are widely recognised to reduce water use on such units but have not been investigated at BP. Many water losses on process units occur because of poor operator management and a focus on increasing efficiency of feed throughput which offers the refinery the greatest financial return. Another inefficient water user in the process category is the Waste Management Area Land Farm. The land farm is irrigated to keep the moisture content of waste high. The exceptionally large volumes of water used in this area can be easily reduced, however costs are considered too high. Finally we assess other uses of water at the refinery. Other uses include commercial and domestic uses, safety showers and the staff carwash. Because of the extraordinary volumes of water used in the refining process, these other uses are considered comparatively insignificant. Practically no water efficiency measures have been taken at this level, and enormous wastages of high quality water are witnessed through our case study of the staff carwash. The carwash is an enormous water waste which uses scheme water once before it is discharged to the sewer.

Each of these case studies shows major inefficiencies in current water management at a number of levels at the BP Refinery in Kwinana. It is important not to forget that this refinery has been recognised for its excellence as a leader in water management not only in the Kwinana Industrial Area but also in the global oil refining industry. This reflects the inherent flaws in water management throughout industry. Chapter 6 assesses management implications associated with reducing water use on site and applies these principles and concepts to industry in general. The most significant barriers to closing industrial water loops were found to be neglect of protection of water sources and larger focus on pollution prevention and wastewater minimisation; misconceptions about the true value of water; and poor regulatory drivers to reduce water use. A paradigm shift in industrial water management to incorporate a more holistic approach is required if water scarcity is to be seriously addressed by industry.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Sustainability
Supervisor(s): Ho, Goen
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