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Removal of organics and metal ion nanoparticles from synthetic 1
wastewater by activated sludge process (ASP) 2
Author: Tarunveer Singh; 3
email id: [email protected], [email protected] ; Affiliation: IIT Delhi 4
Co-author: Shubhanshu Jain; 5
email id: [email protected], [email protected] ; Affiliation: IIT Delhi 6
7
ABSTRACT: Adsorption technique is widely used for removal of toxic organic contaminants from aqueous 8
streams. Owing to the hazardous or otherwise undesirable characteristics of phenolic compounds in 9
particular, their presence in wastewater from municipal and industrial discharge is one of the most 10
important environmental issue. The discharge of poor quality effluents by the chemical-based laboratories 11
and refineries in India is posing a serious threat to water sources and wastewater treatment installations 12
alike. Our study was set up in the Indo-French Unit for Water & Wastewater Technologies (IFUWWT), IIT 13
Delhi. The main objective of this study was to assess the efficiency of a laboratory-scale activated sludge 14
treatment process in producing a final effluent conforming to regulatory standards of Central Pollution 15
Control Board, India (CPCB norms) with regards to COD and metal ion loads. The study was conducted in 16
three principal stages: characterization of wastewater containing nanoparticles; treatability studies of 17
laboratory generated discards and investigations of heavy metal ions before and after treatment. The various 18
raw effluent parameters analyzed were COD, BOD, F/M ratio, Sludge Value Index, Total Solids and 19
concentrations of Cu, Ag and Zn. Studies were conducted using two aerobic sequencing batch reactors 20
(SBR). 21
MLSS of the aeration basin was calculated to be 7180±261.3 mg/L while the F/M ratio was kept down to 22
0.1560±.0149; besides, an SVI of 107.24 mL/g complied with the state of bioreactor’s sludge. These set of 23
values suggested to set an extended aeration processes for the reactors. Accordingly, the detention time in 24
aeration basin was 24 hours. The results showed over 98% influent COD reduction and nearly 100% 25
removal of metal ions. The sample used was operated on sludge collected from Vasant Kunj Wastewater 26
Treatment plant. Based on the results from waste characterization and treatability studies, it was decided 27
that the mixed liquor discharged in the activation tank should have glucose solution and laboratory 28
discarded sample in 1:1 ratio. The reactor was operated on a glucose fed batch basis for 30 days. For the 29
sake of metal analysis, the digested water samples were analyzed for the presence of copper, silver and zinc 30
using the ElementAS AAS4141 Atomic Absorption Spectrophotometer (by Electronics Corporation of India 31
Ltd). The biosorption capacities were found to be over 95% in all the cases with the minimum correlation 32
coefficient for calibration curve being 0.9811. Such a high sludge yield is suggestive of the fact that heavy 33
metals are in very low concentrations in the considered carboy sample. Because of these insignificant values, 34
the amount of metal ions introduced to the system gets adsorbed almost completely, hence leaving behind no 35
metal ion within the supernatant. Well-treated wastewater has enormous potential as a source of water for 36
crops, households and industry. 37
Keywords: Nanoparticles, Activated Sludge Process (ASP), adsorption, bioreactor, F/M ratio, sludge yield, 38
BOD5, COD, Metal ion analysis 39
40
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NOTE : All the charts, figures and graphs haven’t been cited from any other work and are solely the original 41
works of the authors. 42
We first introduce the overview of the project: the scope of project, the desired outcomes and a brief insight 43
into the method used for performing the project. 44
1. INTRODUCTION 45
In many arid and semi-arid countries water is becoming an increasingly scarce resource and planners are 46
forced to consider any sources of water which might be used economically and effectively to promote further 47
development. The wastewater that is generated by the laboratories is characteristically high in both organic 48
and inorganic content. The ability to reclaim wastewater for discharge or reuse would be a giant step toward 49
over-all waste reduction. 50
The conventional methods for treatment of effluents contaminated with heavy metals involve 51 physicochemical processes such as flocculation, precipitation, electrolysis and crystallization. However, 52 these processes are very expensive and generate new products, merely resulting in a transfer of the metal 53
from one medium to another, but not providing a definitive solution. The search for cheaper and definitive 54 solutions led to the development of new technologies based on the utilization of organic substrates for 55
removal of heavy metals by the process of sorption using bioreactors. 56
A bioreactor (BR) may refer to any engineered device or system that supports a biologically active 57 environment. The aim of the study was to set up a vessel in which a chemical process can be carried out, 58 which involves organisms or biochemically active substances derived from such organisms. The sludge used 59
was obtained from Vasant Kunj wastewater treatment plant. To keep the process aerobic, the sludge was kept 60 on aeration throughout. This process is functioned to treat waste water using bacteria which is helped by its 61
food. 62
63
Our first task at hand is to characterize the waste water sample so that we can conclude the viability of the 64 methods we would use to purify it. For this, a series of parameters have been defined and their values have 65
been calculated alongside. 66
2. METHOD 67
68
2.1. CHARACTERIZATION OF CARBOY NANOPARTICLES (NPs) 69
In order to design onsite wastewater treatment systems, we must consider the nature of the 70
wastewater because the effluent quality depends upon the influent characteristics. The treatment 71
capacity and treatment efficiency of systems are calculated based upon the influent concentrations 72
and the effluent requirements. 73
The source of the wastewater influences the characteristics of the waste stream. In general, we can 74
categorize the source as residential, municipal, commercial, industrial or agricultural. The sample for 75
the purpose of our study was a carboy whose constituents were the discarded materials of our 76
laboratory. The components of influent-characterization would be: 77
(i) TSS (ii) BOD5 (iii) COD (iv) Mixed Liquor Volatile Suspended Solid (MLVSS) (v) pH 78
(vi) Calcium and Magnesium content (to check for hardness) and (vii) Metal Analysis 79
TS (Total Solid) 80
Suspended Solid (SS) parameter/Non-Filterable Residue refers to the dry weight of particles trapped 81
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by the Whattman Filter Paper of 45 micron pore size while Dissolved Solid (DS) refers to the dry 82
mass left behind on the filter paper. Their summation gives the net Total Solid content of the waste-83
water. (Table 1) 84
5 Day BOD 85
According to CPCB, the maximum permissible limit of suspended solids for irrigational land is 86
200mg/L while that for inland surface water is 100mg/L. CPCB guidelines state that those water 87
bodies having BOD more than 6 mg/l are identified as polluted water bodies. 88
Biological oxygen demand (BOD) is a measure of the amount of oxygen that is consumed by bacteria 89
during the decomposition of organic matter. Having a safe BOD level in wastewater is essential to 90
producing quality effluent. If the BOD level is too high then the water could be at risk for further 91
contamination, interfering with the treatment process and affecting the end product. By comparing 92
the BOD of incoming sewage and the BOD of the effluent water leaving the plant, the efficiency and 93
effectiveness of sewage treatment can be judged. 94
COD 95
The COD (Chemical Oxygen Demand) test represents the amount of chemically digestible organics 96
(food). COD measures all organics that were biochemically digestible as well as all the organics that 97
can be digested by heat and sulfuric acid. (Table 2) 98
For our purpose, COD was determined using Closed Reflux method (Standard Methods, 1989; 99
Gonzalez, 1986; Jirka and Carter, 1975). In this case, a small volume of sample is heated with 100
concentrated dichromate solution in presence of silver sulphate and mercuric sulphate. The reaction 101
takes place in culture tubes with PTTE-lined screw caps (Fig 1) at 150° C. Heating proceeds for 102
usually shorter times, at higher temperatures than in the open reflux method; the COD is estimated by 103
titrating the digested sample against ferrous ammonium sulphate solution (FAS) in the presence of 104
Ferroin indicator. 105
Determination of trace metal ions by AAS in carboy after pre-concentration and subsequent 106
concentration reduction on adsorption by sludge 107
Samples Tested for presence of heavy metal ions: Our aim was to characterize the carboy 108
nanoparticle sample taking the concentration of three heavy metal ions, namely Cu, Ag and Zn, into 109
consideration. Furthermore, we needed to check if the process of sludge-based-adsorption can prove 110
to be an effective measure to remove these hazardous heavy metals. Hence the metal analyses were 111
done for (a) carboy (b) sludge and supernatant for both reactors. 112
Fig 1. Culture tubes with PTTE-lined screw caps Fig 2. Heating Plate Chamber
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Sample Digestion: To ensure the removal of organic impurities from the samples and thus prevent 113
their interference in analysis, the samples were digested with concentrated nitric acid. 10ml of nitric 114
acid was added to 50ml of sample to be analyzed in a 250ml conical flask. The mixture was 115
evaporated to volume of 5mL by keeping it over a heating plate chamber (Fig. 2) after which it was 116
allowed to cool and then filtered. 117
Standard Preparation 118
(a) Copper: Dissolve 3.7980g of (Cu (NO3)2.3H2O in 250ml. of deionized water. Dilute to 1 liter in 119
a volumetric flask with deionized water. 120
(b) Silver: Dissolve 1.5750 of silver nitrate in 200ml. of deionized water. Dilute to 1 liter in a 121
volumetric flask with deionized water. 122
(c) Zinc: Dissolve 1.2450g of zinc oxide (ZnO) in 5ml of deionized water followed by 25ml. of 5M 123
hydrochloric acid. Dilute to 1 liter in a volumetric flask with deionized water. 124
Sample Analysis: The digested water samples were analyzed for the presence of copper, silver and 125
zinc using the ElementAS AAS4141 Atomic Absorption Spectrophotometer as shown in Fig. 3 (by 126
Electronics Corporation of India Ltd). The calibration plot method was used for the analysis. Air-127
acetylene was the flame used and hollow cathode lamp of the corresponding elements was the 128
resonance line source, the wavelength for the determination of the elements were 217.9nm, 327.5nm 129
and 212.6nm for copper, silver and zinc respectively. The digested samples were analyzed in 130
duplicates with the average concentration of the metal present being displayed in mg/L by the 131
instrument after extrapolation from the standard curve. 132
2.2. EXPERIMENTAL SETUP 133
134
2.2.1. BIOLOGICAL REACTOR SETUP 135
The sludge which provided biomass was obtained from Vasant Kunj Wastewater 136
Treatment plant. To prepare the feed/food for biomass-generation, 1 gram of D-Glucose 137
was added to a liter of water kept on aeration for roughly an hour. This served the purpose 138
for influent COD. 1ml each of MgSO4.7H2O, CaCl2, FeCl3.6H2O and phosphate buffer 139
was next added to the vessel. 1 gram of glucose corresponds to a COD of 1066.67 mg/L of 140
O2. This solution was added by an amount equal to the supernatant decanted from each 141
reactor. The reactors were kept on aeration overnight. Next day, the COD of the 142
Fig 3. ElementAS AAS4141 Atomic Absorption
Spectrophotometer
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supernatant/effluent would be calculated using the closed-reflux-method. The biomass 143
used wasn’t discarded throughout the duration of the study. 144
145
2.2.2. RUNNING ADSORPTION EXPERIMENTS TO STABILIZE COD AND 146
BOD5 147
The overall goal of the activated sludge was to reduce or remove organic matter, solids, 148
ions nutrients, and other pollutants from wastewater. More specifically, the activated 149
sludge process involved blending settled primary effluent wastewater with a culture of 150
microorganisms into fluid called “mixed liquor”. The mixed liquor was discharged in an 151
activation tank, in which air was introduced into the system to create an aerobic 152
environment that kept the activated sludge properly mixed. The bacteria stabilized the 153
substances that had a demand for BOD, while oxidizable chemicals (reducing chemicals) 154
were responsible for consuming COD before being discharged in a clarifier where 155
suspended solids and liquid were separated. 156
157
Oxidizable material + bacteria + nutrient + O2 => CO2 + H2O + oxidized inorganics such as NO3, 158
SO4, etc. 159
160
A number of treatment technologies are in use for the treatment of wastewater contaminated 161
with organic substances. Among them, adsorption process is considered as a promising 162
method for removing COD, heavy metals, colour, odour and ions. This method has aroused 163
considerable interest during recent years for cleaning the wastewater specifically due to its 164
cost-effectiveness. 165
Adsorption in Bioreactor B had been carried out in two stages. For an initial length of 20 166
days, only glucose-based organic feed was added to the reactor. The aim was to acclimatize 167
the microorganisms residing in the reactor to glucose, which served as food for the 168
microorganisms. After this initial set of 20 days, it was seen that the percentage reduction in 169
COD didn’t witness any changes. Hence, it was concluded that the bacteria had become 170
acclimatized. Carboy nanoparticles were now introduced alongside the glucose to the 171
bioreactor B. The ratio for carboy sample to glucose feed was kept at 1:1. This step was 172
prompted due to small concentration of metal ions and had the ratio been kept smaller, the 173
difference between CODs of mixed liquor and Bioreactor A would have been too small. The 174
setup was studied for duration of one week. 175
3. RESULTS 176
177
3.1. CHARACTERIZATION DATA OF CARBOY NANOPARTICLES (NPs) 178
3.1.1. TABLE 1: TOTAL SOLID CONCENTRATION (in mg/L) 179
Date 16/5/2013 29/5/2013 26/6/2013 Average
DS (mg/L) 140 120 100 120
SS (mg/L) 400 460 560 473.33
TS (mg/L) 540 580 660 593.33
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Table 1gives the observed total solid concentration found in the carboy. Over the period of the 180
experiment, this data provides an insight towards the dissolving dynamics. 181
3.1.2. The BOD5 during our study came out to be 697.9949mg/L. The high content of 182
microorganisms and other organic matter lead to consumption of the available oxygen. 183
For the purpose of experiment, we had proceeded with COD monitoring instead of BOD5 184
because of following reasons: 185
(i) BOD5 /COD ratio for June 3, 2013 was 0.373; the result indicated that COD readings 186
are significantly greater than those of 5-day BOD. 187
(ii) Secondly, for COD calculation, the sample needs to be kept in the digestor for only 2 188
hours. BOD calculation requires duration of 5 days, hence being inconvenient. By the 189
time we have results from a 5-day test, the plant conditions would no longer be same. 190
Hence, real time monitor and control cannot be relied upon BOD. 191
192
193
3.1.3. TABLE 2: COD VALUES OF CARBOY NANOPARTICLE SAMPLE 194
Date Blank 1st 2nd 3rd Average Blank-
Average Molarity COD
3/6/2013 1.453 1.42 1.36 1.4 1.393 0.060 0.0975 1871.3
4/6/2013 1.437 1.4 1.4 1.4 1.400 0.037 0.0978 1148.1
5/6/2013 1.437 1.42 1.41 1.4 1.410 0.027 0.0975 831.7
6/6/2013 1.447 1.42 1.44 1.43 1.430 0.017 0.0975 519.8
7/6/2013 1.467 1.46 1.45 1.45 1.453 0.013 0.0971 414.2
11/6/2013 1.473 1.42 1.42 1.41 1.417 0.057 0.0973 1763.9
12/6/2013 1.447 1.41 1.39 1.38 1.393 0.053 0.0975 1663.4
13/6/2013 1.500 1.44 1.47 1.44 1.450 0.050 0.0975 1559.5
14/6/2013 1.460 1.43 1.44 1.42 1.430 0.030 0.0975 935.7
17/6/2013 1.470 1.43 1.44 1.47 1.447 0.023 0.0967 722.1
20/6/2013 1.450 1.42 1.42 1.45 1.430 0.020 0.0977 625.0
21/6/2013 1.450 1.43 1.43 1.43 1.430 0.020 0.0990 633.7
24/6/2013 1.463 1.45 1.41 1.46 1.440 0.023 0.0971 724.9
25/6/2013 1.433 1.4 1.44 1.41 1.417 0.017 0.0978 521.9
26/6/2013 1.417 1.4 1.4 1.41 1.403 0.013 0.1000 426.7
27/6/2013 1.440 1.43 1.42 1.44 1.430 0.010 0.0996 318.7
195
After June 6, a certain amount of laboratory discarded waste was again feeded to the aging 196
carboy to regenerate it. This explains the visible bump in COD readings in Table 2. The 197
constant decrement in the COD values can be attributed to decomposition of organic wastes 198
and oxidation of chemical waste. 199
In accordance with the CPCB guidelines, the maximum permissible Chemical Oxygen 200
Demand of Inland Surface Water could be 250mg/L and for drinking purposes, it comes down 201
to 3 mg/L. With respect to these values, the given carboy sample can be categorized to be 202
highly contaminated as its initial COD value is over 1500 mg/L. This result was expected as 203
the constituents of the carboy are formed by laboratory-discards. 204
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GRAPH 1: REDUCTION OF CHEMICAL OXYGEN DEMAND (in mg/L) OF CARBOY 205
206
COD values for the initial phase (June 3 to June 7) varied between 1871 mg/L to 414.2 mg/L 207
as can be seen in Graph 1. 208
Before examining metal-ion analysis, it is important to understand the primary role of 209
activated sludge i.e. the reduction of chemical oxygen demand (COD) from domestic 210
wastewater. 211
212
3.2. ATTRIBUTES OF NORMAL REACTOR (BIOREACTOR A) 213
214
TABLE 3: CALCULATED STRENGTH OF INFLUENT ADDED TO THE REACTORS (in mg/L) 215
Date Blank 1st 2nd 3rd Average
Blank-
Average
Molarity Influent
30/5/13 1.463
0.0969 1066.667
31/5/13 1.427
0.0990 1066.667
3/6/13 1.453
0.0975 1066.667
4/6/13 1.437
0.0978 1066.667
5/6/13 1.437
0.0975 1066.667
6/6/13 1.447 1.38 1.37 1.36 1.370 0.077 0.0975 1195.582
7/6/13 1.467 1.39 1.39 1.4 1.393 0.073 0.0971 1139.159
11/6/13 1.473 1.38 1.42 1.41 1.403 0.070 0.0973 1089.494
12/6/13 1.447 1.38 1.37 1.38 1.377 0.070 0.0975 1091.618
13/6/13 1.500 1.37 1.46 1.46 1.430 0.070 0.0975 1091.618
14/6/13 1.460 1.37 1.39 1.39 1.383 0.077 0.0975 1195.582
17/6/13 1.470 1.4 1.4 1.41 1.403 0.067 0.0967 1031.593
19/6/13 1.447 1.39 1.37 1.37 1.377 0.070 0.0977 1093.750
20/6/13 1.450 1.34 1.39 1.43 1.387 0.063 0.0990 1003.300
21/6/13 1.450 1.36 1.37 1.37 1.367 0.083 0.0971 1294.498
24/6/13 1.463 1.38 1.36 1.4 1.380 0.083 0.0978 1304.631
25/6/13 1.433 1.37 1.36 1.36 1.363 0.070 0.1000 1120.000
26/6/13 1.417 1.34 1.37 1.36 1.357 0.060 0.0996 956.175
27/6/13 1.440 1.35 1.38 1.38 1.370 0.070 0.1006 1126.761
216
217
0.0
500.0
1000.0
1500.0
2000.0
11/6/2013 12/6/2013 13/6/2013 14/6/2013 17/6/2013 20/6/2013 21/6/2013 24/6/2013 25/6/2013 26/6/2013 27/6/2013
COD (in mg/L of O2)
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218
219
COD removal and sludge yield 220
Simply due to the high number of microorganism in bioreactors, the pollutants uptake rate can 221
be increased. This leads to better degradation in a given time span; also the required reactor 222
volumes are smaller. In comparison to the conventional activated sludge process (ASP) which 223
typically achieves 95 percent removal, average COD removal by Reactor-A over a course of 224
30 days came out to be 98.186%. The readings have been presented in Table 3. Such a high 225
sludge yield could be attributed to high MLSS concentration. Graph 2 presents the 226
comparative idea of COD influent properties. 227
F/M ratio and dissolved oxygen (DO) concentration has a big influence to on microorganism 228
growth in activated sludge process. A rapid growth causes bulking sludge which is indicated 229
by a High SVI value. 230
231
Calculating F/M ratio 232
The term Food to Microorganism Ratio (F/M) is actually a measurement of the amount of 233
incoming food (kg of Influent CBOD) divided by the kg of microorganisms in your system. In 234
our calculations, the volume of activated sludge in our clarifiers has been taken as the total 235
amount of microorganisms exposed to the incoming food. 236
237
Volume of supernatant removed everyday = 500ml/L 238
⇒volume of microbial-sludge exposed = 500ml/L 239
Volume of feed added to each reactor = 500ml (net volume of feed prepared = 1L) 240
241
TABLE 4: TSS VALUES FOR REACTOR A 242
DATE SS (Suspended
Solids) in mg/L
DS (Dissolved
Solids)
in mg/L
Microorganism (M)
available in mg/L
May 28, 2013 6685 680 7365
May 29, 2013 6285 710 6995
0.000
200.000
400.000
600.000
800.000
1000.000
1200.000
1400.000
COD (in mg/L of O2)
GRAPH 2: CALCULATED STRENGTH OF INFLUENT ADDED TO THE REACTORS (in mg/L)
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Average 6485 695 7180
Aeration system volume = 500ml ⇒ M = (7180 mg/L)*(.5 L) = 3590 mg 243
F = Flow * Influent COD = (500 mL/day)*(1066.67 mg/L) = 533.335 mg/day 244
⇒ F/M = 533.335/3590 = 0.148 245
The numerical value of food has been shown in Table 4. 246
247
Normally, we prefer a low F/M ratio due to the following advantages: (i) High degree of 248
elimination of BOD5 and COD (ii) Good nitrification/de-nitrification (iii) Good settle-ability 249
to sustain shock and toxic loading. 250
251
Extended aeration processes generally operate within the following ranges: 252
ƒ Detention time in aeration basin = 12-24 hrs. 253
ƒ MLSS in aeration basin = 2000-5000 mg/L 254
ƒ System F: M Ratio = 0.05 – 0.15: 1 255
Hence the setup is within the permissible limits. 256
257
258
TABLE 5: PERCENTAGE COD REMOVING CAPACITY OF REACTOR-A 259
Date Blank 1st 2nd 3rd Average Blank-
Average Molarity
COD
left
%
Removal
5/29/2013 1.470 1.38 1.37 1.38 1.377 0.093 0.0975 29.110
5/30/2013 1.463 1.40 1.35 1.40 1.383 0.080 0.0969 24.806
5/31/2013 1.427 1.37 1.38 1.40 1.383 0.043 0.0990 13.729 98.713
6/3/2013 1.453 1.39 1.34 1.39 1.373 0.080 0.0975 24.951 97.661
6/4/2013 1.437 1.39 1.37 1.40 1.387 0.050 0.0978 15.656 98.532
6/5/2013 1.437 1.41 1.41 1.41 1.410 0.027 0.0975 8.317 99.220
6/6/2013 1.447 1.42 1.43 1.40 1.417 0.030 0.0975 9.357 99.123
6/7/2013 1.467 1.41 1.39 1.41 1.403 0.063 0.0971 19.676 98.354
6/11/2013 1.473 1.40 1.43 1.43 1.420 0.053 0.0973 16.602 98.543
6/12/2013 1.447 1.42 1.41 1.41 1.413 0.033 0.0975 10.396 99.046
6/13/2013 1.500 1.45 1.39 1.45 1.430 0.070 0.0975 21.832 98.000
6/14/2013 1.460 1.43 1.44 1.42 1.430 0.030 0.0975 9.357 99.143
6/17/2013 1.470 1.39 1.42 1.40 1.403 0.067 0.0967 20.632 98.274
6/19/2013 1.447 1.41 1.40 1.41 1.407 0.040 0.0977 12.500 98.788
6/20/2013 1.450 1.42 1.39 1.41 1.407 0.043 0.0990 13.729 98.745
6/21/2013 1.450 1.38 1.42 1.42 1.407 0.043 0.0971 13.463 98.658
6/24/2013 1.463 1.36 1.34 1.38 1.360 0.103 0.0978 32.355 97.501
6/25/2013 1.433 1.33 1.32 1.36 1.337 0.097 0.1000 30.933 97.629
6/26/2013 1.417 1.34 1.34 1.34 1.340 0.077 0.0996 24.436 97.818
6/27/2013 1.440 1.26 1.24 1.25 1.250 0.190 0.1006 61.167 93.603
260
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The abnormal reductions in removing capacity towards the end in Table 5 can a result of 261
overburdening of the sludge biomass, indicating the need to replace the sludge. 262
263 264
265 266
GRAPH 3 & 4: BEHAVIOUR OF GLUCOSE FEED ON BEING TREATED BY BIOREACTOR-A 267
0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0
31/5/2013
3/6/2013
4/6/2013
5/6/2013
6/6/2013
7/6/2013
11/6/2013
12/6/2013
13/6/2013
14/6/2013
17/6/2013
19/6/2013
20/6/2013
21/6/2013
24/6/2013
25/6/2013
26/6/2013
27/6/2013
13.7
25.0
15.7
8.3
9.4
19.7
16.6
10.4
21.8
9.4
20.6
12.5
13.7
13.5
32.4
30.9
24.4
61.2
1066.7
1066.7
1066.7
1066.7
1066.7
1195.5
1139.2
1089.5
1091.6
1091.6
1195.6
1031.6
1093.8
1003.3
1294.5
1304.6
1120.0
956.2
COMPARISON BETWEEN INITIAL COD OF GLUCOSE FEED AND AFTER BEING
TREATED USING BIOREACTOR-A
INITIAL COD OF FEED COD LEFT AFTER ADSORPTION FROM BIOREACTOR
90.000 91.000 92.000 93.000 94.000 95.000 96.000 97.000 98.000 99.000 100.000
31/5/2013
4/6/2013
6/6/2013
11/6/2013
13/6/2013
17/6/2013
20/6/2013
24/6/2013
26/6/2013
PERCENTAGE REMOVAL OF GLUCOSE FEED BY BIOREACTOR
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Graph 3 provides an observation of behavior of glucose feed on being treated by bioreactor A. The 268
percentage removal is very high as is evident from Graph 4. 269
270
Calculating Sludge Volume Index (SVI) ratio 271
Sludge Volume Index (SVI) is an extremely useful parameter to measure in a wastewater treatment 272
process. In simple terms, SVI is the result of a mathematical calculation. It takes into account the 30-273
minute settle-ability test result and the activated sludge mixed liquor suspended solids (MLSS) test 274
result to come up with a number (or index) that describes the ability of the sludge to settle and 275
compact (Figure 4). 276
277
Value of Sludge Volume Index can then be calculated from the formula given here. Whereby, 278
279
280
281
282
283
284
285
286
TABLE 6: SLUDGE VOLUME INDEX CALCULATION 287
SV (Volume of settled solids in one-liter graduated transparent measuring
cylinder after 30 minutes settling period) in mL/L
770 mL/L
MLSS (Mixed liquor Suspended Solids) in ppm 7180 mg/L
SVI (Sludge Volume Index) in mL/g 107.24 mL/g
288
According to tpo (treatment plant operator) guidelines, cases wherein SVI is in the range of 289
100 to 200 mL/g, as is the case in Table 6, activated sludge plants seem to produce a clear, 290
good-quality effluent which supports the observation of 98.186% removal of COD feeded. 291
Fig. 4 : Sludge Volume Index Calculation
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Such a sludge typically settles more slowly and traps more particulate matter as it forms a 292
uniform blanket before settling. It also supports the growth of microbial culture. 293
294 FIG 5: REACTOR WHEN KEPT ON AERATION FIG 6: REACTOR WITH SETTLED SLUDGE 295
296
3.3.ATTRIBUTES OF MIXED LIQUOR REACTOR (BIOREACTOR B) OR 297
EFFECT OF NANOPARTICLE WASTEWATER ON COD 298
TABLE 7: CHEMICAL OXYGEN DEMAND OF EFFLUENT FROM BIOREACTOR b 299
Date Blank 1st 2nd 3rd
Average Blank-
Average
Molarity
COD (in
mg/L of O2)
29/5/2013 1.470 1.38 1.37 1.38 1.377 0.093 0.0975 29.110
30/5/2013 1.463 1.39 1.39 1.38 1.387 0.077 0.0969 23.773
31/5/2013 1.427 1.39 1.37 1.37 1.377 0.050 0.0990 15.842
3/6/2013 1.453 1.42 1.39 1.45 1.420 0.033 0.0975 10.396
4/6/2013 1.437 1.39 1.37 1.40 1.387 0.050 0.0978 15.656
5/6/2013 1.437 1.40 1.39 1.40 1.397 0.040 0.0975 12.476
6/6/2013 1.447 1.31 1.28 1.40 1.330 0.117 0.0975 36.387
7/6/2013 1.467 1.41 1.39 1.39 1.397 0.070 0.0971 21.748
11/6/2013 1.473 1.43 1.44 1.45 1.440 0.033 0.0973 10.376
12/6/2013 1.447 1.40 1.39 1.41 1.400 0.047 0.0975 14.555
13/6/2013 1.500 1.47 1.47 1.47 1.470 0.030 0.0975 9.357
14/6/2013 1.460 1.42 1.43 1.45 1.433 0.027 0.0975 8.317
17/6/2013 1.470 1.41 1.45 1.43 1.430 0.040 0.0967 12.379
19/6/2013 1.447 1.40 1.40 1.40 1.400 0.047 0.0977 14.583
20/6/2013 1.450 1.41 1.41 1.35 1.390 0.060 0.0990 19.010
21/6/2013 1.450 1.42 1.44 1.36 1.407 0.043 0.0971 13.463
24/6/2013 1.463 1.45 1.41 1.43 1.430 0.033 0.0978 10.437
25/6/2013 1.433 1.39 1.39 1.38 1.387 0.047 0.1000 14.933
26/6/2013 1.417 1.38 1.40 1.39 1.390 0.027 0.0996 8.499
27/6/2013 1.440 1.37 1.42 1.39 1.393 0.047 0.1006 15.023
300
From June 21 onwards, the mixed liquor feeded to Bioreactor B (Figure 5 and 6)consisted of 250 mL each 301
of Glucose and Carboy sample, while Bioreactor A was continued to be fed with 500 mL of glucose feed 302
only. The COD of mixed liquor supplied to the bioreactor B for June 25 is calculated by taking the mean of 303
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(a) carboy’s COD for June 24 and (b) COD of glucose feed prepared on June 25. COD of mixed liquor for 304
other days was similarly calculated. 305
TABLE 8: COD OF INFLUENT AND EFFLUENT ASSUMING BIOREACTOR AS THE 306
TREATMENT UNIT AND MIXED LIQUOR AS THE DISPOSAL WHICH REQUIRES 307
TREATMENT 308
0.000
5.000
10.000
15.000
20.000
25.000
30.000
35.000
40.000
Effluent COD (in mg/L) of Bioreactor B
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309
310
GRAPH 7: Percentage COD removal (before introducing Carboy nanoparticles to Bioreactor B) 311
As in the above two figures (Graph 7 and 8), high percentage COD removal signifies high sludge yield. 312
98.515
99.025
98.532
98.830
96.589
98.181
99.089
98.664
99.143
99.238
98.965
98.586
98.262
98.658
90.000 91.000 92.000 93.000 94.000 95.000 96.000 97.000 98.000 99.000 100.000
31/5/2013
3/6/2013
4/6/2013
5/6/2013
6/6/2013
7/6/2013
11/6/2013
12/6/2013
13/6/2013
14/6/2013
17/6/2013
19/6/2013
20/6/2013
21/6/2013
Percentage COD removal (before introducing Carboy nanoparticles to Bioreactor B)
0.000 200.000 400.000 600.000 800.000 1000.000 1200.000
31/5/2013
4/6/2013
6/6/2013
11/6/2013
13/6/2013
17/6/2013
20/6/2013
15.842
10.396
15.656
12.476
36.387
21.748
10.376
14.555
9.357
8.317
12.379
14.583
19.010
13.463
1066.7
1066.7
1066.7
1066.7
1066.7
1195.5
1139.2
1089.5
1091.6
1091.6
1195.6
1031.6
1093.8
1003.3
G R A P H 6 : C O M P A R I S O N B E T W E E N I N I T I A L C O D O F G L U C O S E - F E E D A N D C O D A F T E R T R E A T M E N T U S I N G B I O R E A C T O R - B ( B E F O R E
I N T R O D U C I N G C A R B O Y N A N O P A R T I C L E S )
INITIAL COD OF FEED COD LEFT AFTER ADSORPTION FROM BIOREACTOR B
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90.000 92.000 94.000 96.000 98.000 100.000
24/6/2013
25/6/2013
26/6/2013
27/6/2013
Percentage COD removal of Mixed Liquor
GRAPH 8 & 9: EFFLUENT COD IS NEARLY INSIGNIFICANT AS COMPARED TO INFLUENT COD 314
INDICATING HIGH ADSORPTION CAPACITY OF THE ACTIVATED SLUDGE. 315
It is evident that the domestic wastewater remains polluted with organic load plus the 316
dissolved and suspended matter. Organic load is reflected in terms of the COD and the BOD 317
values. In the present investigations only reduction of the COD was discussed. The COD 318
concentrations, 739mg/L to 1014mg/L (Graph 8 and9), in the wastewater were substantially 319
higher than that of the permissible limit [100–200 mg/l, for irrigation and horticultural uses 320
according to the Central Pollution Control Board, India (CPCB norms)]. 321
322
3.4.FATE OF METAL IONS OF NANOPARTICLE WASTEWATER IN 323
BIOLOGICAL REACTOR 324
325
TABLE 9: CONC. v/s ADSORBANCE VALUES FOR Ag (λ=327.5 nm) 326
Concentration (ppm or mg/L) Absorbance
0.00 0.010
0.50 0.050
1.00 0.104
1.50 0.186
2.00 0.201
2.50 0.260
327
328
329
330
331
332
24/6/2013
25/6/2013
26/6/2013
27/6/2013
10.4
14.9
8.5
15
969.2
1014.8
739.1
776.7
COMPARISON BETWEEN INITIAL COD OF MIXED LIQUOR AND
COD AFTER TREATMENT USING BIOREACTOR-B)
y = 0.102x + 0.0077 R² = 0.9811
0
0.1
0.2
0.3
0 1 2 3
Ab
sorb
ance
Concentration
absorbance
absorbanceLinear…
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333
Silver nanoparticles were found to be absent from carboy and glucose solution. Concentration 334
of copper nanoparticles in the carboy was found out to be 0.064 mg/L (Table 9) . This reading 335
is very insignificant when compared to CPCB parameters. The corresponding experiment 336
readings are shown in Table 10. 337
338
TABLE 10: Studying Efficiency of Bioreactor A to adsorb Zn heavy metal
Concentration
(ppm or mg/L) Carboy glucose Sludge Supernatant
Sludge +
Supernatant
Biosorption Capacity of
sludge (in percentage)
21/6/2013 0.645 0 0.371 0.027 0.398
24/6/2013 0.612 0 0.589 0.030 0.619 95.35
25/6/2013 0.576 0 0.704 0.000 0.704 100.00
26/6/2013 0.561 0 0.934 0.000 0.934 100.00
27/7/2013 - 0 1.109 0.016 1.125 97.15
339
340
Conc.(ppm) absorbance
0.00 0.005
0.40 0.151
0.60 0.222
0.80 0.272
1.00 0.339
TABLE 11/GRAPH11: CONC. v/s 341
ADSORBANCE VALUES FOR 342
Zn (λ=212.6 nm) 343
344
345
346
347
Another set of readings suggest that when on glucose-based feed was added to the Bioreactor-B, no 348
notable changes were noticed in metal ion’s concentration of both supernatant and sludge. 349
Calibration curves were obtained using a series of varying concentrations of the standards for both 350
the metals. The two calibration curves were linear with correlation coefficients of 0.996 and 0.9811 351
(Graph 11). The initial biosorption capacities were 95.35% and 100%. The subsequent sludge yield 352
y = 0.3317x + 0.0121 R² = 0.996
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.00 0.20 0.40 0.60 0.80 1.00 1.20
Ab
sorb
ance
Rat
io
Concentration (ppm or mg/l)
Caliberation Curve
plot ofadsorbance v/sconc.Best Fit LinearModel
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continues to be very high owing to aging of sludge and the fact that we are dealing with heavy metals 353
which have very low concentrations. Because of these insignificant values, the amount of metal ions 354
introduced to the system gets adsorbed almost completely, hence leaving behind no metal ion within 355
the supernatant. 356
357
For the protection of human health, guidelines for the presence of heavy metals in water have been 358
set by different International Organizations such as USEPA, WHO, EPA, European Union 359
Commission (Marcovecchio et al., 2007), thus, heavy metals have maximum permissible level in 360
water as specified by these organizations. Maximum contaminant level (MCL) is an enforceable 361
standard set at a numerical value with an adequate margin of safety to ensure no adverse effect on 362
human health. It is the highest level of a contaminant that is allowed in a water system. The two 363
elements that were studied in this research namely: Zinc and Silver have Maximum Contaminant Levels 364
of 5mg/L and 0.10 mg/L for drinking purposes (according to National Secondary Drinking Water 365
Regulations). 366
4. REFERENCES 367
[1] Asli Baysal, Nil Ozbek and Suleyman Akman (2013). Determination of Trace Metals in Waste 368
Water and Their Removal Processes 369
370
[2] Gary Lee Mishoe (1999). F/M Ratio and the Operation of an Activated Sludge Process 371
372
[3] Guidelines for Water Quality Management. CENTRAL POLLUTION CONTROL BOARD 373
‘PARIVESH BHAWAN’, EAST ARJUN NAGAR, DELHI 374
375
[4] RANI DEVI and R. P. DAHIYA (2005). Chemical Oxygen Demand (COD) reduction in domestic 376
wastewater by fly ash and brick kiln ash. 377
[5] M.A. Momodu and C.A. Anyakora. Heavy Metal Contamination of Ground Water: The Surulere 378
Case Study. 379
[6] E S Ju´lio, F Branco and V D Silva (2003). Structural rehabilitation of columns with reinforced 380
concrete jacketing 381
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