Recycling Treated Municipal Wastewater for Industrial Water Use

o Synthetic medium
o Two-stage
Surface Filtration
TM3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
Surface filtration has been used for the same purposes as depth filtration, with more
specific application in the removal of algae and other suspended solids from
stabilization pond effluents. In surface filtration, particulate matter is removed by
passing water through a filter material, in a mechanical sieving process. Cloth fabrics,
woven metal fabrics, and various synthetic materials have been used as the filter
material. This subsection focuses on the cloth media filters. Membranes and cartridge
filters are also surface filters and are discussed in subsequent subsections.
The cloth media surface filters used are known under the names of Cloth-Media Filter
(CMF), Discfilter (DF), and the diamond cloth-media filter (DCMF). The CMF, by
Aqua-Aerobic Systems under the trademark name AquaDisk, uses either a needle felt
cloth of polyester or a synthetic pile fabric cloth. The cloth covers several disks
mounted vertically in a tank. Water flows by gravity from the exterior of the disks
through the filter media to an internal collection system. The DF, by Veolia Water
Systems under the trademark name Hydrotech, brings water through the central feed
tube and the effluent exits on the exterior of the disks. The cloth screen material is
either polyester or Type 304 or 316 stainless steel. A more recent product on the
market is the DCMF. The cloth filter elements, which have a diamond shaped cross
pattern, are cleaned by a vacuum sweep moving along the length of the filter.
Membrane Filtration
Membrane filtration is a fast-growing sector of the filtration market for potable water
treatment, wastewater treatment, and water reuse applications. The number of
potable water systems in the upper Midwest has increased dramatically over the past
decade. Full-scale membrane bioreactor (MBR) WWTPs are also in operation and are
an integral part of the facility planning for new and expanding WWTPs in Minnesota.
Factors influencing the use of membranes at WWTPs include: a smaller footprint is
required, a reduction (or elimination) of chemicals or energy use for disinfection, and
use of secondary effluent for water reuse applications.
Membrane filtration is a general term that encompasses a wide range of filtration
types. The common feature is the use of a thin membrane for the purpose of removing
constituents from water. Membrane processes include microfiltration (MF),
ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and electrodialysis
(ED). This subsection focuses on MF and UF as unit processes in place of depth and
surface filtration for removal of suspended particulates. NF, RO, and ED are processes
that also remove dissolved solids, as depicted in Figure 4, and discussed in
subsequent sections.
Craddock Consulting Engineers 11
In Association with CDM & James Crook
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