Effect of soy protein-based flocculant on flocculation and
filtration of diatomite and kaolin suspensions
Hideo Maruyama and Hideshi Seki
ABSTRACT
The effect of ethylated soy protein-based bioflocculant (EtSP) as a filter aid reagent was investigated.
The efficiency of EtSP as a filter aid was evaluated in terms of the specific cake resistance, α, and was
compared with chitosan and polyaluminum chloride (PAC). Diatomite and kaolin were used as model
particles. Total filtration resistance, R, decreased with increasing flocculant dosage (wt.%, flocculant/
particle) and was almost constant in the range of 1 wt.% or more for both particles. The α value was
significantly decreased from 1.01 × 10
11
to 9.01 × 10
10
m/kg for diatomite and from 5.11 × 10
10
to
5.20 × 10
9
m/kg for kaolin by the addition of EtSP in the case of 1.0 wt.%. The α value for cakes
formed by EtSP was much smaller than that formed by chitosan and PAC. In the case of diatomite, in
the dose range of 0.5–1.0 wt.%, the α value for cakes formed by EtSP and chitosan was almost the
same. However, at the excess dose of 2.0 wt.% over, the α value formed by chitosan abruptly
increased. In the case of kaolin, in the dose range of 1.0–2.0 wt.%, the α values of chitosan and PAC
were mostly the same, however, these values were larger by ca. nine times than that of EtSP.
Key words | biodegradable flocculant, ethylated protein, filter-aid flocculant, flocculation filtration,
soy protein, specific cake resistance
HIGHLIGHTS
•
The proposed filtration model was verified by experimental results.
•
Evaluation of the efficiency of EtSP as a filter aid by the specific cake resistance, α.
•
The α value by EtSP was much smaller than that by PAC at proper dosages.
Hideo Maruyama (corresponding author)
Hideshi Seki
Division of Marine Bioresources, Graduate School
of Fisheries Sciences,
Hokkaido University,
Minato-cho 3-1-1, Hakodate 041-8611, Hokkaido,
Japan
E-mail: maruyama@fish.hokudai.ac.jp
NOMENCLATURE
A filtration area [m
2
]
V filtrate volume [m
3
]
t time [min]
ΔP pressure drop across filter [Pa]
R total filtrate resistance [m
–1
]
R
c
cake resistance [m
–1
]
R
m
medium resistance [m
–1
]
S cross sectional area of filtration apparatus [m
2
]
h
0
initial height of suspension [m]
g gravitational acceleration [m/min
2
]
V
T
total volume of suspension [m
3
]
C solid concentration in suspension [kg/m
3
]
α specific cake resistance [m/kg]
μ viscosity of the fluid [kg/(m s)]
ρ density of suspension [kg/m
3
]
INTRODUCTION
Removal of suspended solids by filtration plays an important
role in wastewater treatment (Nishi et al. ), tap water
production (Zouboulis & Katsoyiannis ; Fiksdal &
Leiknes ; Jeong & Vigneswaran ), and downstream
processes (Khouni et al. ) in various industries.
Sometimes, during the filtration process, small particles
penetrate deeply into the filter media and cause premature
1868 © IWA Publishing 2020 Water Science & Technology | 82.9 | 2020
doi: 10.2166/wst.2020.461
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