This lecture discusses about the TS and Dissolved content in wastewater and its removal methods

1. Wastewater – dissolved
materials – Physical
removal methods
Lecture 8
By
Dr. S. PUGALENDHI & Er. T. AYISHA NAZIBA

2. Wastewater
 Water generated after the use
of freshwater, raw water, drinking
water or saline water in a variety of
deliberate applications or processes.
 Used water from any combination of
domestic, industrial, commercial or
agricultural activities, surface runoff /
storm water, and any sewer inflow or sewer
infiltration".
 In everyday usage, wastewater is commonly
a synonym for sewage - produced by a
community of people.

3. Solids in wastewater
 Total solids = dissolved solids + suspended and settleable solids.
 Domestic sewage - 99.9 percent water + 0.1 percent, contains a wide variety of dissolved and
suspended impurities.

4. • Fixed Solids - those solids (total, suspended or dissolved) which remain after ignition for 15 to 20
minutes time at 550 ± 50°C. - inorganic material
• Settleable Solids - material settling out of a sample within a one-hour period. - floating material
• Total Dissolved Solids - those solids which will pass through a standard glass fiber filter with a
pore size of 2 microns or less.
• Total Solids - material left in a dish after evaporation of a sample and its subsequent drying in an
oven at a defined temperature. Total solids = "Total Suspended Solids" + "Total Dissolved Solids".
• Total Suspended Solids - those solids which will not pass through a standard glass fiber filter with
a pore size of 1.5- 2 microns - non-filterable residue.
• Volatile Solids - those solids which are lost during ignition (in a sense, by burning) for 15-20
minutes at 550℃ ± 50℃ - organic material.

5. Dissolved solids
 TDS in wastewater refers to
dissolved organic matters and
inorganic salts, including sodium,
potassium, calcium, magnesium,
chloride, bicarbonates, and
sulfates (Zhang et al., 2017).

7. Screening
 Screening is the first unit operation used at
WWTPs.
 Screening removes objects such as rags,
paper, plastics, and metals
 to prevent damage and clogging of
downstream equipment, piping, and
appurtenances

8. Types
Coarse Screens Fine Screens
• Remove large solids, rags, and debris
• Openings of 6 mm (0.25 in) or larger.
• Types - mechanically and manually cleaned bar screens,
including trash racks.
• Hand cleaned - at small facilities-high flow / repair or
maintenance of mechanical screening
• Mechanically cleaned - increase efficiency and reduce
problems
• Chain Driven Screens - front and back chain driven
screens can rake from upstream or downstream.
• Catenary Screens - front return, front cleaned
chain driven screens -straightforward, internal
mechanics to prevent further jamming
• Reciprocating Rakes - climber screen – alternate
multiple rake - less efficient facing heavy loads
• Continuous belt screen - Ultra-high tech,
functional and efficient
• Removes material that may create
O&M problems in downstream
processes (lack primary treatment).
• Opening sizes for fine screens are
1.5 to 6 mm (0.06 to 0.25 in).
• Very fine screens with openings of
0.2 to 1.5 mm (0.01 to 0.06 in)
placed after fine screens to reduce
suspended solids levels
 Drum Screens (rotating
cylinders in the flow channel)
 Step Screens (fixed and
movable plates across the width
of the channel)
 and Static Wedge Wire Screens
(used by large treatment plants
with ample floor space)

9. Comminution
 Comminutors (grinders, macerators) are used
to reduce the particle size
 It consist of a rotating slotted cylinder through which
wastewater flow passes.
 Solids that are too large to pass through the slots are
cut by blades as the cylinder rotates, reducing their
size until they pass through the slot openings. of
wastewater solids.
 Screens were light and subject to puncturing.
 Incapable of handling the increasingly heavy solids
encountered due to low power and a lack of torque

10. Types
 Drum Type Comminutors.
 Straight-through Comminutors
 In-line Comminutors/Grinders
 Dual Shaft Comminutors (Grinders)
 Cutter Cartridge Enhanced Twin
Shaft Comminutors.

11. Sedimentation
 The purpose of sedimentation is to
enhance the filtration process by
removing particulates.
 Sedimentation is the process by
which suspended particles are
removed from the water by means
of gravity or separation.
compression.
concentration and
relative tendency of the
particle to interact
discrete particle
flocculent particles
hindered or zone

12. Flotation
 Flotation is known as a separation process, based on the
introduction of gas bubbles as the transport medium.
 Suspended particulate matter, being hydrophobic or
conditioned to be so, is then attach to the bubbles and
moves toward the water solution surface
 i.e., contrary to the direction of gravity
 Natural Flotation: density difference which is naturally
sufficient for separation.
 Aided Flotation: external means are used to promote
the separation of particles that are naturally floatable.
 Induced Flotation: density of particles is artificially
reduced to allow particles to float.
 Dissolved Air Flotation (DAF) is a method of induced
flotation with very fine air bubble or microbubbles
which are up to 40 to 70 microns

13. Filtration
 Removes particles and other media
of a certain size and larger from
liquids.
 Removing these particles and debris
from a wastewater system allows the
water to be reused within that
system
 Types
 Sand
 Cartridge
 reverse osmosis
 Bag
 Membrane filter

14. THANK YOU