Removal of organics and metal ion nanoparticles …113 Sample Digestion: To ensure the removal of organic impurities from the samples and thus prevent 114 their interference in analysis,

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

PeerJ PrePrints | http://dx.doi.org/10.7287/peerj.preprints.451v1 | CC-BY 4.0 Open Access | received: 6 Aug 2014, published: 6 Aug

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mailto:[email protected]




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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