A comparative life cycle assessment of process water treatment technologies at the Secunda industrial complex, South Africa

Abstract

The increasingly poor quality of South Africa's natural water sources requires industries and power stations to treat raw water extensively prior to industrial use in, for example, boilers. Two different raw water desalination technologies, an existing ion exchange plant and a proposed reverse osmosis intervention, are compared by life cycle assessment for the production of 1 Mℓ of boiler feed water, in the context of the Secunda industrial complex situated in Mpumalanga, South Africa. The proposed reverse osmosis option would perform 22% worse for global warming potential, which relates to the use of coal-derived electricity, but would reduce burdens of the ion exchange option on human toxicity and freshwater aquatic ecotoxicity due to the use of an aluminium sulphate coagulant. Significantly, the assessment predicts the reverse osmosis option to effect a 78% overall reduction in storage of problematic salts, from 599 kg/Mℓ to 133 kg/Mℓ. Notwithstanding the fact that the power generated within the complex and used by the RO process is associated with a high salts burden (mine water is desalinated at the power station), it was found that the reverse osmosis intervention would incur a lower salts footprint than the IX/S technology and would not shift salts burdens.

Environmental life cycle assessment for potable water production – a case study of seawater desalination and mine-water reclamation in South Africa

“…Zhou et al (2014) present an extensive review of the international studies employing LCAs for desalination and they include more than 30 individual research papers. Locally, there are only two such investigations (Friedrich, 2002;Ras and Von Blottnitz, 2012) that employ LCA for the use of membranes in the treatment of water. However, there are no such investigations for the local desalination of seawater or reclamation of mine-affected water.…”

Life cycle inventory data generation by process simulation for conventional, feedstock recycling and power-to-X technologies for base chemical production

“… Cooling water is applied in a closed cycle with water loss of 2% due to evaporation [19] . Boiler feed water is prepared by membrane separation processes, adapted from [20] with utility demand per t BFW: 1.175 t Fresh water, 0.66 kWh electricity. Table 5 Process characteristics for the fixed-bed slagging gasification process.…”

Chemical and Energy Recovery Alternatives in SWRO Desalination through Electro-Membrane Technologies

“…For example, an SWRO plant located in the Mediterranean area requires 0.2-0.5 g•m −3 of freshwater of HCl and 30-60 g•m −3 of freshwater of NaOH [33]. Although H 2 SO 4 is commonly used in desalination plants due to its low price, it has certain disadvantages, such as the high scaling potential of sulfate [62,63], so replacing it with HCl is an interesting alternative, even more so if an in-situ production is considered. Thus, electro-membrane technologies could contribute to the self-supply of chemicals and energy in a desalination facility.…”