REMOVAL OF NUTRIENTS AND HEAVY METALS FROM URBAN WASTEWATER
USING AERATION, ALUM AND KAOLIN ORE
M.N. Rashed and M.E. Soltan
Chemistry Department, Faculty of Science, 81528 Aswan, Egypt.
E-mail: mnrashed@hotmail.com-
ABSTRACT
Some urban wastewater resulted from domestic and industrial wastewater and needs special
treatments before discharge to surface water or used for irrigation. This study is target to use
kaolin (from south Egypt) as adsorbent for the removal of heavy metals as well as aeration
and alum for the removal of nutrients from Kima drain wastewater .The experiment proceeds
through 3 steps, the first step applied the aeration method for 24,48,120 and 192 hr and
obtained the suitable time to remove or reduce the nutrients. Second step includes treatment
with alum [KAl(SO4)2.12H2O] using different alum doses (50,100 &150 mg/l) at the obvious
times to remove or reduce the nutrients , while the third one includes treatment with kaolin
ore size <63 µm at different doses, pH and times to remove heavy metals. The results revealed
that aeration method removed CO3 ,OH and Mn ions , and reduced pH, Ca,Cl, NO2, SiO2,
PO4, Na and Fe concentrations. Treatment with alum was effective for the removal of
CO3,OH, NO3,PO4 ions and reduced Cl, F, Na, Cd, Cu, Cr, Sr, and Zn . Kaolin ore was very
effective as adsorbent for reduced and removal of the heavy metals Cd, Cr, Cu, Ni, Pb, Sr and
Zn from the wastewater. Using the three consecutive treatment processes ,we obtained
wastewater in the range of standardized limits for discharge into surface water or used in
irrigation as cited by Egyptian Authorities.
KEYWORDS
Heavy metals- kaolin - pollution- treatment- urban water- wastewater.
INTRODUCTION
Water pollution is responsible for the death of some 25 million people each year
(Niemczynowicz, 1999) and cause a destroy of aquatic environment. The major point of water
pollution was wastewater, especially urban wastewater, these urban wastewater come from
varied sources include domestic wastewater from houses, hospitals and commercial uses as
well as agricultural and industrial wastewater. These wastewater contains inorganic pollutants
such as nutrient and heavy metals and causes pollution to the surface water. So, many studies
were run to eliminate or reduce these pollutants before its discharge or reuse for irrigation.
Wild and Stefist (1999) studied the simulation of nutrient fluxes in wastewater treatment plant
with EBPR. Alum was used with ferric chloride as coagulators for the wastewater treatment
(Ngtez et al, 1999). Many alkalis were currently being used for environmental control
purposes particularly in wastewater treatments (Estefan, 1992), the most commonly used were
lime and sodium carbonate. Natural ores were also used for wastewater treatment, zeolites
were used for removal of heavy metals from wastewater (Yuan et al,1999). Ajmal (1995) was
used naturally occurring pyrolusite for adsorption of Pb , Zn and Mg from industrial
wastewater.
This study is target to apply a continuos three treatment processes on urban wastewater
collected from Kima drain (canal received wastewater from fertilizer factory, houses and
hospital uses) which consider as a source of pollution in river Nile water. These processes are:
1. Treatment for reduce or removal of nutrients using aeration process.
2. Treatment for the removal or reduce of both remain nutrients and heavy metals using alum
(potassium aluminum sulfate) [KAl(SO4)2.12H2O].
3. Treatment for the removal of heavy metals using kaolin ore which found in a large
quantity at Aswan (south of Egypt) .
Moreover, this study is target also to obtain treated wastewater in the range of ruse for
irrigation or discharge on surface water as cited by Egyptian Authorities.
EXPERIMENTAL
Sample collection
Wastewater samples .The wastewater samples were taken from Kima drain. Wastewater
samples were collected by dipping pre-cleaned glass jars into the drain stream and collected in
20-L plastic container. Samples were placed in coolers and transported to the laboratory.
Kaolin ore samples. Kaolin ore samples (5 Kg of each) were collected from Kalabsha area
(80 km south of Aswan city ,Egypt ). The ore was crushed using a mechanical crusher and
ball mill. Then grinding by using an electric agate mortar. The powdered ore was sieved in
sieve <63 m.
Treatment experiment using aeration and alum
Twenty liters of wastewater samples were inserted in two glass jars (40x40x40 cm). 50 mg/l
of alum (potassium aluminum sulfate) was added to the one jar every 24 hr till 192 hr , while
the air was pumped in the another jar for 192 hr. The samples were analyzed after every
addendum in the jar of alum and every known times 24,48,120 and 192 in the aeration jar.
Treatment experiment using kaolin ore
Adsorption studies. To choose the desired size of high adsorption capacity, one gram sample
of the operating size <63 m was washed with 50 ml bidistilled water three times,then treated
with 50 ml of solution containing 10 ppm mixture standard of Cd,Cr,Cu, Mn, Pb and Zn in a
conical flask. Constant stirring of the solution was maintained for 24 h. After attainment of
equilibrium,the content of the flask was filtered through Whatman 0.45m cellulose nitrate
membrane filter and susequently analysed for residual concentrations of the metal ions using
atomic absorption spectrophotometer (SP1900 Pye Unicam)The concentration of adsorbed
metal ions were calculated from the known total amount of adsorbate added .
Effect of concentration. After choosing the ore size that had maximum adsorption
capacity,the kaolin was treated with 50 ml mixture heavy metals standards (10,8,4,2 &1 ppm)
in a conical flask for 24 h. After attainment of equilibrium,the content of the flask was filtered
through Whatman 0.45m cellulose nitrate membrane filter, and metal ions were analysed
using atomic absorption spectrophotometer. The adsorption capacity was calculated.
Effect of pH on adsorption.One gram of the kaolin sample was treated with 50 ml of 10 ppm
standard mixture, then the pH of the adsorption mixture was adjusted to various pH values (3,
5 ,7& 9) by using 0.5 M NaOH or 0.5 M HCl.The final concentration of the metals were
determined after 24 h and the adsorption capacity was calculated.
Effect of ore dosage. 0.25, 0.5,1 and 2 gm of kaolin was treated with 50 ml of 10 ppm
standard mixture. The final concentration of the metals after 24 h were determined using
AAS, and the adsorption capacity was calculated. After determined the suitable dose and time
of alum, as well as, the optimum aeration time, kaolin (<63µm) experiment was applied on
wastewater sample to obtain the ideal pH, dose and time for treatment.
Standard solutions:
Certified atomic absorption spectroscopic standard solution as Cd,Cr,Cu, Mn, Pb and Zn
(1000 ppm) was purchased from BDH Company,UK. Working standard solutions 10,8,4,2 &
1 ppm were prepared by diluting the stock one.
Analytical measurements:
The original wastewater sample and the samples resulted from each treatment were analyzed
for pH, conductivity, ions CO3,OH, Cl, SO4,PO4,NO3,SiO2, F, Na, Ca, Mg, and Fe
according to standard methods . Heavy metals Cd, Cr, Co, Cu, Sr , Mn , Pb and Zn were
analyzed using Atomic absorption spectrophotometer, SP1900 Pye Unicum.
RESULTS AND DISCUSSION
Wastewater treatment using aeration method:
The results of wastewater treatment experiments (Table 1) show that aeration method
exhibited high efficiency (100%) after 120 hr for complete removal of CO3, OH and Mn ions,
while it reduced the concentrations of pH, Ca, Cl, NO3, SiO2, PO4, Na and Fe at different
times; Ca 44.8-42.4 mg/l and NO3 42-34 mg/l after 48 hr, SiO2 17-8.5 mg/l and Cl 76.5-6.3
mg/l after 120 hr . The chloride removal was as the result of the adsorption of some metal
chlorides on the precipitate. Nitrate removal efficiency was decreased after 48 hr then
increases as the time increased; this increase may be due to oxidation of free ammonia to
nitrite that oxidized to nitrate (Wakeel&Wahby, 1970). Nitrate ground water was reduced by
the addition of 315-mish iron and buffered at pH 8.8 (Cheng et al, 1997). PO4 was removed
after 192 hr (100% removal efficiency) , this was due to either precipitation of Ca and Al
phosphate or adsorption of phosphate on the hydrous iron oxide ( Furumal & Ohgakl , 1989).
Maximum reduction of SiO2 observed after 120 hr . Sodium removal efficiency increased up
to 24 hr and decreased as the time forward, this decrease was as the result of the adsorption of
Na ions on the negative precipitated charge. pH decreased from 9.14 (initial wastewater
concentration) to 6.89 after aeration time 120 hr ,as the results of acidic effect of the air CO 2
(Soltan,1991). Heavy metals Fe, Cd, Cr, Cu , Sr and Zn have not regular trends in the
treatment efficiency with aeration , but nearly all reached maximum efficiency in the time
range 48-120 hr.
Table 1: Treatment efficiency (%) of the study items in the wastewater.
Time.
Methods.
Ions
PH
CO3
OH
Cl
PO4
NO3
SiO2
Ca
Na
Fe
Cd
Cr
Cu
Sr
Mn
Zn
A
24 hr
B
3.51
27.7
100
83.6
22.6
138
31.7
96.4
66.3
5.75
23.3
33.3
150
73.3
50
75
5.04 44.45 100 83.6 62.7 100
58.8 96.4 64.1 5.75 92
20 100
33.3 100
200 100
66.6 94
100
100
87.5 88
C
A: Treatment with aeration.
A
6.68
55.5
100
91.6
47.9
80.9
43.9
94.1
63
3.45
33.3
66
50
80
100
87.5
48hr
B C
9.09 86.1 100 91.6 75.8 100 18.2 96.4 66.3 21.8 93
20 100
33.3 100
0.0 100
73.3 92
100 100
37.5 87
120hr
A
B
12.라
100
100
91.6
96.5
114
50
100
63
82.7
36.6
33.3
0.0
93.3
100
62.5
12.9
100
100
91.6
100
100
48.2
104
59.9
69.9
46.6
33.3
50
73.3
100
25
129hr
A
B
24.6
23.7
100
100
100
100
91.6
91.6
100
100
138 111
48.2
32.9
118 128
63
58.7
81.6
56.3
40
66.6
66.6
66.6
150
150
86
93
25
75
25 50
B: Treatment with Alum. C: Treatment with kaolin
These metals may be adsorbed on the colloidal precipitate formed in the solution.
Constructed wetlands was used to treat some toxic wastewater under tropical conditions,
which remove more than 99% of Cr and Ni concentrations ( Polprasert et al,1996). Single and
two stage aerated system was used for the removal of nitrogen from wastewater (% N2
efficiency removal 95%)(Andreadakis et al, 1995).
Wastewater treatment using alum method:
Effect of time. The effect of time in wastewater treatment with alum is shown in Table 1. The
results revealed complete removal of OH, NO3, Mn and Cu after 24 hr , while CO3 and NO3
after 120 hr. The method reduced the concentrations of SiO2 and Zn after 24 hr, while it
reduced Na after 48 hr, and Cl, F, Cd, Sr and Cr after 192 hr. Initial phosphate concentration
in the sample was 3.7 mg/l which exhibited fast removal in alum method (after 120 hr) than
those aeration (192 hr) (Table 2).This decrease was due to either precipitation of Ca and Al
phosphate or adsorption of phosphate on hydrous aluminum oxide ( Ngtez et al,1999).
Hydroxyl ion OH initial concentration was completely removed after 24 hr, this remove
resulted when the addition of alum ,it furnishes Al+3 ion in solution which discharge the
hydroxyl OH negative ion . Remove of Mn was as the result of it's consume in oxidation
process by microorganisms. The decrease of Co, Cu, Cr, Cd, Fe, Pb and Zn were as the result
of redissolved of the suspended or colloidal dehydrated oxide as a result of pH decreases
(Ajmal et al, 1992).
Table 2: Nutrient levels ( ppm )in original and treated samples and Egyptian standard .
Sample
pH
Original sample
Aeration treatment
Alum treatment
Egyptian Standard
CO3 OH
Cl
NO3 PO4
9.14 144 768 76.5 42
3.7
6.08 0.0 0.0 63 34
0.0
6.92 0.0 0.0 63 0.0 0.00
6-9 ---1
30
1
SiO2
17
8.5
8.8
---
Ca
44.8
42.4
43.2
--
Na
F
46
0.3
17
0.42
15.5 0.06
--1.0
Effect of alum dose. Figures 1 and 2 show the effect of alum dose (50,100 & 150 mg/l) on
removal efficiency of ions. For CO3, OH, Cl, PO4,NO3, SiO2 , Na and Ca ions the suitable
alum dose observed was 100 mg/l , while for heavy metals, the suitable alum dose was 50
mg/l . Alum dose of 100 mg/l for 120 hr was sufficient for complete removal of CO3, OH and
Mn, and reduce the concentrations of Cl , PO4, SiO2, Na and Ca. The obvious heavy metals
were less reduced by alum method (30-50% efficiency removal), but more effective than
aeration method. Possible component of the (SPM) suspended particle matter, such as Al, Fi,
Fe and Mn oxides or hydroxides, were known to have substantially different binding affinities
for metals (Ferreira et al, 1997). The effects of size and geochemical properties on the binding
of trace metals to natural colloids and particles have been investigated in which Cd was more
strongly bound to the smallest fraction than Cu (Lead et al, 1999).
Fig.2 Effe ct of alu m dose on trace
e le m e n ts e ffi ci e ncy tre atm en t
120
120
% Efficiency treatment
% Efficiency treatment
Fig.1 : Effe ct of alu m dose on n u trie n ts
e fficie n cy tre atm e n t
50m g/l
100m g/l
150m g/l
100
100
80
60
40
20
80
60
40
20
0
Fe
0
CO3 OH
Cl
PO4 NO3 SiO2 Ca
Cd
Cr
Cu
Sr
Zn
Pb
Na
Treatment using kaolin method
Effect of initial metal concentrations. From Table 3 ,it was shown that Cr , Cd , Cu and Pb
undergo complete adsorption (100%) at kaolin surface for all the initial element standards.
For remaining elements, Mn maximum adsorption observed with Mn initial concentration 10
ppm, while for Sr, Fe and Zn, maximum adsorption was observed from 8 ppm Sr , Fe and Zn
standards. Parkman et al (1998) reported that per cent uptake of Sr on kaolinite was greatest at
the highest initial Sr concentration.
Effect of pH. The adsorption of the heavy metals on kaolin at different pH was performed
using 10 ppm standard mixture elements. The results (Fig.3) show that the adsorption of the
studied heavy metals increased as pH increase from 3 -6.5, the maximum adsorption of the
metals observed at pH < 7. After pH 7 the metals adsorption decrease as the result of
precipitation of these metals.
Table 3: Effect of initial heavy metals concentration on adsorption efficiency
Element initial
Concentration(ppm)
1
2
4
8
10
Mn
Sr
94
95.5
91.7
95.5
97
98
95
93
99
91
Fe
99
100
98.7
100
99.5
Cr
Pb
% Adsorption
100
100
100
100
100
100
100
100
100
100
Cd
Zn
100
100
100
100
100
Cu
99
100
100 100
98.7 100
100 100
99.5 100
Other study on the adsorption of heavy metals on the biomass of Phormidium sp was suitable
at pH 5 for Pb, Cu, Cd, Zn and Ni (Wang et al, 1998), the maximum adsorption was 13,600
mg/kg for Pb; 10,100 mg/kg for Cu; 9,600 mg/kg for Cd ; 9,400 mg/kg for Zn and 5,700
mg/kg for Ni. Ajmal et al (1995) reported the maximum adsorption of Pb ,Zn and Cd on
pyrolusite under pH 7. The optimum pH for removal of Cd, Cu and Mo using carbonaceous
material, developed from the waste slurry generated from fertilizer plant, was about pH 6, for
Cr and Hg was at pH 2, while for Pb it was almost in the range 6-7 (Srivestava et al, 1989).
Effect of kaolin dose. Using different dose of kaolin (0.5, 1, 1.5 and 2 gram) for the
adsorption technique, suitable kaolin dose for the maximum adsorption of the studied heavy
metals was obtained (Fig.4). It shown that the adsorption of Fe, Cd, Cr, Co, Cu, Sr, Mn and
Pb increased as the kaolin dose increase and reach maximum at 2g.
Fig. 4 : Effe ct of k aolin dose on the he avy
m e tal ads orption
Fig. 3 : Influnce of pH on heavy m etal
ads orption on k aolin
120
100
Sr
Fe
Cr
Pb
Cd
Zn
Cu
10
1
3
5
pH
7
9
% Adsorpion
% Adsorption
100
Mn
Sr
Fe
Cr
Pb
Cd
Zn
Cu
80
60
40
20
0
0.5
1
1.5
Kaolin dos e
2
Langmiur adsorption isotherm. Langmuir equation was used as the model for adsorption, the
adjusted Langmuir equation in its linear form being (Bohn et al, 1985)
1/(x/m)= 1/c b + 1/a
(1)
where c (mg/kg) , is the concentration of adsorbate left in solution at equilibrium,
x/m(mg/kg) ,is the amount of adsorbate adsorbed per unit mass of adsorbent,
a
,is Langmuir binding energy coefficient, and
b (mg/kg) , is the adsorption maximum.
Parameters (a ) and ( b ) can be obtained from the equation (Table 4 ). it was shown that the
adsorption maximum parameter using kaolin (a) was the highest for Fe, while the lowest was
for Mn .Zinc adsorption maximum was less than of Fe and Sr. Kaolin binding energy (b) was
nearly the same for Fe, Zn and Sr ,while binding energy for Mn was the lowest . This mean
that Fe and Zn was higher bounded to kaolin than Mn and Sr. Correlation coefficient (R2)
,obtained from Langmuir isotherms, were positive
Table 4: Langmuir parameters for the adsorption of heavy metal on kaolin
Ions
Adsorption maximum
a (mg/kg)
Binding energy
b (mg/kg)
Mn
Fe
Zn
Sr
2.62
1666
1000
90.9
0.557
1.007
1.006
1.003
R2 for
Langmuir equation
0.224
0.999
0.999
0.999
and highly significant. Other study (Wang et al, 1998) on the heavy metals binding and
removal by Phormidium sp biomass reported the highly maximum adsorption, calculated
from Langmuir isotherm, was for Pb (13,600 mg/kg) and Cu (10,100 mg/kg), while it was
nearly the same for Cd (9,600 mg/kg) and Zn (9,400 mg/kg ).
Wastewater treatment using kaolin. After concluded the suitable conditions for the
adsorption of heavy metals Fe, Cd, Cr, Co, Cu, Sr, Mn and Pb on kaolin using standard
solution, Kima drain wastewater was applied for the removal of heavy metals using kaolin.
Treatment with kaolin ore size <63 µm exhibited the high efficiency for the complete removal
of heavy metals. The adsorption per cent (Table 5) was 100% for Cd, Cu, Cr, Mn and Pb.
Kaolin reduce the concentration of Fe, Sr and Zn (adsorption per cent 92%, 94 % and 88 %
respectively). Kaolin treatment method was very effective for the removal of heavy metals Fe,
Cd, Cr, Co, Cu, Sr, Mn and Pb than aeration and alum methods (Table 5). Various low cost
adsorbents reported to be effective for the removal of heavy metals from wastewater,
Fe(III)hydroxide was used for the removal of Cr ,Ni ,Cu , Cd and Zn from electroplating
wastewater (Ajmal et al,1992).
The results of the wastewater treatment processes (Table 5) were in the limits cited by
Egyptian Authority for discharge into surface water or reuse for irrigation.
Table 5: Heavy metals levels (ppb) in Alum treatment samples and Egyptian standard.
Sample
Fe Cd
Cu
Cr
Sr
Mn
Pb
Original sample
430 30
22
32
150 40
32
Alum treatment
30
0.0
0.0
0.0
10
0.0 0.0
Kaolin treatment
1
0.0
0.0
0.0 0.80 0.0 0.0
Egyptian Standard*
1000 ppb
*Egyptian limits for treated wastewater discharge to surface water ,law 48
protection of the river Nile.
Zn
80
10
0.9
of the year 1982 for the
CONCLUSION
Continuous treatment processes, aeration, addition of alum and adsorption at kaolin surface,
were developed for removal of nutrients and heavy metals. Aeration and alum processes were
effective for the removal or reduce of nutrients, while kaolin process was very effective for
removal of Cd, Cu, Cr , Mn and Pb and reduced the concentrations of Fe , Sr and Zn. The
results of the wastewater treatment processes were in the limits cited by Egyptian Authority
for discharge into surface water or reuse for irrigation.
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