MBR and Sludge glossary (S)

SAD
Specific aeration demand

SAE
Standard aeration efficiency (kgO₂/kWh)

SAF
Submerged aerated filter

SBR
Sequencing batch reactor

SCADA
Supervisory control and data acquisitions

Screw press SP
Sludge dewatering technology based on conveying sludge along the length of a cylindrical screen using an Archimedean screw

SDI
Silt density index

SED
Specific energy demand

SED_m
Specific energy demand for membrane aeration

SEDA
Specific energy demand for aeration

SEM
Scanning electron micrograph

Septicity
Decay and putrefaction under anaerobic (i.e. oxygen-depleted) conditions

Settling velocity
The velocity of a particle settling in water under gravity

Severity factor
Factor expressing the rate of increase and intensity of heat

SGD
Specific gas demand

SGD_m
Specific gas demand – membrane area (in Nm³ gas/(hr.m²))

SGD_p
Specific gas demand – permeate volume (in Nm³ gas/m³ permeate)

Shear rate
Rate of imposed shear, the force associated with water flowing parallel to the particle or floc surface

Slow pyrolysis
Non-oxidative thermochemical treatment employing low heating rates and moderate temperatures favouring bio-char as the main product

Sludge drying
Removal of water from sludge by evaporation at elevated temperatures

Sludge stabilisation
Reduction of odour, putrescence (i.e. decay) and pathogenic organism content of sewage sludge

sMBR
Sidestream membrane bioreactor

SMP
Soluble microbial product

SMP_c
Soluble microbial product (carbohydrate)

SMP_p
Soluble microbial product (protein)

SNdN
Simultaneous nitrification and denitrification

Solar dryers
Equipment for removing water from sludge through its evaporation at elevated temperatures

Solar drying bed SDB
Sludge drying bed housed in a glass-based structure to allow control of the drying atmosphere

Solid bowl centrifuge
Centrifuge based on a rotating horizontal cylinder with a conical end where the sludge cake exits

Solids loading rate SLR
Amount of solids fed into the reactor per volume per unit time

Solids mass concentration
Percentage solids content or mass of solids per unit volume of sludge

Solids reduction
Reduction of solids content of sludge through its decomposition to thermal products

Solids retention time SRT
Period of time the solids are retained in the reactor

Solubilisation
Dissolving of matter in water

SOTE
Standard oxygen transfer efficiency

Specific resistance
Hydraulic resistance of the cake formed from sludge solids to the passage of water through it

Specific resistance to filtration SRF
Measure of hydraulic resistance

Sticky phase
Phase of the drying cycle where the sludge becomes sticky and challenging to manipulate

STP
Sewage treatment plant

Supercritical region
Region of the water temperature:pressure phase diagram above 218 bar pressure and 374 °C temperature in which water exists as a supercritical fluid or plasma

Supercritical water gasification SCWG
Another term for 'hydrothermal gasification'

Supercritical water oxidation SCWO
Oxidation taking place in the supercritical region of the temperature:pressure water phase diagram (above 218 bar pressure and 374 °C temperature)

Supernatant
Diluted (water) upper layer produced when solids settle

Surface water
Water associated with solid particles and bound to their surfaces by hydrogen bonding

SUVA
Specific UV absorbance per unit organic carbon concentration

SVI
Sludge volume index

SW
Spiral-wound

Syngas
Primary product of hydrothermal gasification (HTG), containing gaseous hydrogen and carbon monoxide as the primary constituents

Synotrophy
A biochemical symbiotic relationship