Chemical Engineering September 2020 - 39

Feature Report
designing an
integrated wastewatertreatment
system
Meeting the wastewater-treatment demands of an integrated manufacturing complex demands
a design that can address a diverse array of contaminants and discharge requirements
a
ny large, integrated chemical-manufacturing
complex will
require the
implementation of a comprehensive
wastewater-treatment solution
to address unique wastewater challenges
and comply with all necessary effluent discharge
requirements. this article outlines
the process for designing and commissioning
such a wastewater-treatment facility,
using real-life examples from sasol's new
chemical-production plant in westlake, la.,
near lake charles. the facility produces liquid
fuels from coal, and includes a 1.5-million-ton/
yr ethane cracker and six downstream chemical
plants that will produce chemicals for plastics
and other consumer products. the downstream
chemical-production facilities include
two large polymers plants (low-density and
linear low-density polyethylene); an ethylene
oxide/ethylene glycol plant; and three smaller,
higher-value derivative plants that produce
specialty alcohols, ethoxylates and alumina
products. For any project of this magnitude,
efficient wastewater treatment is essential in
supporting effective plant operation.
Initial technology evaluation
prior to building the lake charles complex,
sasol launched a technology evaluation program
that spanned five years. the purpose
of the program
was
to investigate
a range
of options
for treating
gas-toliquid
(gtl)
wastewa -
ters. after
ident i fying
membrane
bior eac -
tor (mBr)
technology
(Figure 1)
as the most
ef fective
solution, sasol invested heavily in mBr piloting,
modeling and technology validation,
which led the company to select a specific
ultrafiltration (uF) hollow-fiber membrane
(Figure 2) as the mBr technology
of choice for addressing gtl wastewater
treatment needs.
FIGURE 2. The MBR used in this project
featured special hollow-fiber ultrafiltration
(UF) membrane cassettes
FIGURE 1. Membrane bioreactor (MBR) technology integrates
membrane solids separation with a suspended-growth biological
process in a bioreactor
Treatment train design
drawing from a broad portfolio of technologies
to use in conjunction with mBr, a fully
integrated multi-train wastewater treatment
system was selected (Figure 3), with the
objective to achieve a consistently treated
effluent that would meet all local, state and
federal regulations in terms of discharge
quality. Following an initial equalization stage,
to equalize the incoming waste streams, a
dissolved-nitrogen flotation (dnF) unit was
selected as a pre-treatment solution for oil
and solids separation.
it is critical to guard against free oil in the
incoming wastewater, and generally, free oil
ChemiCal engineering www.Chemengonline.Com September 2020
39
Brian Arntsen
sueZ water
technologies &
solutions
In BrIef
initial technology
evaluation
treatment train
design
water-treatment
plant design
plant startup and
commissioning
operational data
http://www.Chemengonline.Com
Chemical Engineering September 2020

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