Physicochemical characterization of the sewage sludge from guarchia wastewater treatment plant in benghazi-libya evaluation of the organic composition

Physicochemical characterization of the sewage sludge from guarchia wastewater treatment plant in benghazi-libya evaluation of the organic compositionSubmit Manuscript | http://medcraveonline.com
Introduction Until the late 19th century, there has been much concern with the
effective and safe disposal of the mankind liquid and solid wastes. The installation of sewerage systems for piping liquid wastes away from major population centers was the single greatest contributor to the dramatic reductions in infectious diseases which occurred during that time. The liquid wastes were usually discharged untreated to a river or the ocean but, with the increasing world population, improved sanitary systems and the adventure of more stringent standards on wastewater treatment, this option has become increasingly untenable.1–2
The processes applied to the treatment of sewage result in the separation of sewage into two streams, a clarified water containing 20-30mg/l of suspended solids and a sludge stream of 1-3% solids dry weight, which contains 80-90% of nutrients and pollutants present in the raw sewage.1 The nature of the sewage sludge varies, depending on both the wastewater composition (mainly organic and inorganic materials, plant nutrients, trace elements, organic chemicals and some pathogens) and on the treatment processes used.3 Recent studies involved qualitative and quantitative evaluation of wastewater,9 the degradation kinetics of sewage sludge,8 the reuse application of wastewater,10–11 the study of Chemical and Microbial Composition of Municipal Sewage water, the Hydrogen and Methane Production from Biowaste and Sewage Sludge and finally the study of the impact of sewage treatment plant on local environment.12–14 Our current research paper deals with the investigation of the total organic composition of the raw sewage sludge samples collected from sixteen wastewater pumping stations at Benghazi city and from Guarchia wastewater treatment plant to evaluate pH, The total nitrogen (TN), the total phosphorus (TP), The total organic matter (TOM) and the total organic carbon (TOC).
Aim of the work Wastewater generated by Benghazi is generally pumped to
Guarchia treatment plant for treatment. Only one quarter of the pumped quantity of this wastewater can be accepted and partially
treated by Guarchia treatment plant, due to its limited capacity and low efficiency, producing unstabilized sewage sludge; which will be disposed-off in open fields, and partially treated effluent, which together with the remained untreated waste-water will be discharged into stream at the Mediterranean Sea in front of the city; the discarded materials contain potential toxic constituents, particularly heavy metals and organic compounds. So far, no efforts to purify water have been conducted in the region. Efficient waste management practices that include potential hazard minimization, recovery operations and treatment prior to stream emission should be implemented. The lack of suitable waste treatment results in discharge of untreated or inadequately treated municipal and industrial sewage into aquatic environment, leading to deleterious health effects. So far, no controls on emissions of pollutants to the environment have been set in the city, although the country established laws and regulations related to water sources conservation since 1973.
Concerning the health and environmental effects of organic chemicals in sewage sludge, the exposure to organic pollutants; for example through drinking water, is very low. However, as some of these compounds may be bio-accumulated or have effects at low concentrations, chronic health effects are starting to be investigated for some of these compounds. In the current research work, the main objectives of the study are:
1. Determination of some physicochemical properties of sludge such as pH, percent of water content, total volatile solid, total nitrogen, total phosphorus, total organic matter and total organic carbon.
2. To describe the monthly and the spatial variations of sludge properties.
3. To find-out the relationships between sludge properties.
Benghazi city contains about 36 wastewater-pumping stations out of which only sixteen pumping stations and Guarchia treatment plant were chosen as sampling points for our research. A monthly sample was collected from every station during the period of Jan-Mar.
MOJ Biorg Org Chem. 2017;1(2):3048. 30 © 2017 Azzouz et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially.
Physicochemical characterization of the sewage sludge from guarchia wastewater treatment plant in benghazi-libya evaluation of the organic composition
Volume 1 Issue 2 - 2017
Abd Alsalam H Azzouz, Nuha A Naas, Khalid M Darwish Chemistry Department, University of Benghazi, Libya
Correspondence: Khalid M Darwish, Chemistry Department, Science Faculty, University of Benghazi, Benghazi, Libya, Email [email protected] Received: April 24, 2017 | Published: May 26, 2017
Abstract
Raw sewage sludge collected from sixteen wastewater-pumping stations at Benghazi city and from Guarchia wastewater treatment plant have undergone physicochemical characterizations including pH, total volatile solid (TVS), total nitrogen (TN), total phosphorus (TP), total organic matter (TOM) and total organic carbon (TOC). The monthly and spatial variations in sludge properties have also been described.
Keywords: physicochemical characterization, guarchia wastewater treatment plant, organic composition
MOJ Bioorganic & Organic Chemistry
Research Article Open Access
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©2017 Azzouz et al.
Citation: Azzouz AAH, Naas NA, Darwish KM. Physicochemical characterization of the sewage sludge from guarchia wastewater treatment plant in benghazi- libya evaluation of the organic composition. MOJ Biorg Org Chem. 2017;1(2):3048. DOI: 10.15406/mojboc.2017.01.00009
(2006) and another monthly sample was collected from Guarchia plant during the period of Dec. 2005 -Jan. 2006. For determining the total organic composition, each dried sample was ground with glass pestle and mortar then passed through a 2mm mesh stainless steel sieve. The dried ground samples were then stored in plastic bags into a refrigerator for analysis.4 The required temperature for TN, OM and TP determination was 500C. The pH, TS and TVS for each sludge sample were measured directly after sample collection with no need for drying.5
Total solid content (TS) The water content is a measurement of sediment moisture expressed
as a percentage of the whole sediment weight. The sediment moisture content equals the difference between wet weight of the sediment and dry weight following oven drying at 50-1050C to a constant weight.6
' (as % of wet sludge) ) (1 0 0
wt TS
wt =
Where wt’ is weight of sample after drying; wt is weight of sample before drying.
Total volatile solids (TVS) This represents the fraction of total solids lost up on ignition at a
temperature of 550±100C for 1h.6
Where wt’ is weight lost during ignition; wt is weight remaining after drying.
' ( % ) (100)
wt =
Where wt’ is weight lost during ignition; wt is weight remaining after drying.
Organic matter and organic carbon in dried sewage sludge (OM% & OC%)
This involves reduction of K2Cr2O7 by OC-compounds followed by determination of unreduced dichromate by redox titration by ferrous ammonium sulfate. The actual measurement is of oxidizable OC but the data are converted to percentage OM using a constant factor, assuming that OM contains 58% of OC. However, since this proportion is not constant, the results are multiplied by 1.334 as OC.4
10 blank
N V
Where N=Normality of ferrous ammonium sulfate (~ 0.5M)
10=Volume of (1N) K2Cr2O7 solution
Vblank=Volume of ferrous ammonium sulfate solution required to titrate the blank (in ml)
Vsample=Volume of ferrous ammonium sulfate solution required to
titrate the sample (in ml)
wt = weight of dried sludge (g)
0.3=3×10–3 × 100; where 3 is the equivalent weight of C.
Total nitrogen (TN %) in dried sludge Applying Kjeldahl semi micro methods, using 50ml Kjeldahl
digestion flask, for TN analysis of sediments, the sample must be more finely ground and thoroughly mixed than for the macro- Kjeldahl analysis to minimize sample error.7 The method involves digestion of sample to convert organic-N to inorganic-N as (NH4
+-N) then determination of TN in the digest as (NH4
+-N). The digestion involves heating the sample with H2SO4-containing substances that promote oxidation of OM and conversion of organic-N to inorganic-N (NH4
+-N), being salts such as K2SO4 or Na2SO4, which increase the temperature of digestion, and catalysts such as Hg, Cu, or Se, which increase the rate of oxidation. The (NH4
+-N) is determined by collecting the NH3 liberated by distillation with alkali and analyzing the distillate by titrimetric procedure.7
( ) 0.14
' 10
1
0
x =
Where wt’ is weight of TN (NH4 +-N) in sample; wt is weight
of sample; V is volume of H2SO4 required for titration and %N is percentage of TN in sample.
Total phosphorus in dried sludge The molybdophosphate complex is formed in H2SO4 matrix
and reduced with ascorbic acid and absorbance is measured at 840- 880nm. The color is stable from 10min to 24h after formation.4 The sample (0.3-0.5g) in an uncovered crucible was ignited in a muffle at 5500C for 2h. After cooling in desiccator, the sample was transferred to a 100ml calibrated flask, where 50ml of HCl (1N) was added.
The mixture was filtered after shaking overnight for 14-18h at 250C. A solution of ascorbic acid in ammonium molybdate (8ml) was added to the filtrate. Absorbance of the solution was measured at λmax using 1cm cuvette. A standard curve was prepared by analyzing aliquots of a KH2PO4 solution.
( ) ( ) 1. Abs F D
Conc of P wt × ×
=
Where Abs = absorbance of sample solution; F1 = factor of standard curve (x/y); D=Dilution factor; wt=weight of sample after ignition.
Results and discussion In station 1, the pH values ranged between 6.16 in February and
6.68 in January (generally acidic). The organic matter concentration was in the range of (21.74-27.23 %), the maximum content was recorded in March and minimum was in February. The lowest content of TN was determined in March (1.52 %) and the highest content was determined in January (2.75 %). At the same time, the lowest value of TP was recorded in March (1.78 %) and the highest value was recorded in February (2.95 %). The C/N ratios were ranging from 3.63 in January to 10.36 in March, due to the changes of OC % contents during the study period (Table 1) (Figure 1).
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Table 1 Monthly variations in the sludge properties at station
Parameter Jan. Feb. Mar. Min. Max. Average STD deviation
pH 6.68 6.16 6.48 6.16 6.68 --- 0.262
OM% 23.67 21.74 27.23 21.74 27.23 24.21 2.785
OC% 13.73 12.6 15.76 12.60 15.76 14.03 1.601
TN% 2.75 1.69 1.52 1.52 2.75 1.98 0.666
C/N 3.63 7.45 10.36 3.63 10.36 7.14 3.375
TP% 2.07 2.97 1.78 1.78 2.97 2.27 0.620
Figure 1 The C/N ratios were ranging from 3.63 in January to 10.36 in March.
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In station 2, the pH values ranged between 6.21 and 6.73 (acidic range). The maximum record of OM was obtained in March (47.81%) and the minimum was found in January (44.39%). the contents of TN% were ranging from 3.78 to 4.20%. The contents of TP% at this
station were ranging between 1.35% in January and 1.93% in March. Records of C/N ratio were ranging from 6.34 in January to 7.16 in February (Table 2) (Figure 2).
Table 2 Monthly Variations in the Sludge Properties at Station 2
pH 6.73 6.36 6.21 6.21 6.73 --- 0.267
OM% 44.39 46.72 47.81 44.39 47.81 46.30 1.747
OC% 25.74 27.09 27.68 25.74 27.68 26.83 0.994
TN% 4.06 3.78 4.20 3.78 4.20 4.01 0.213
C/N 6.34 7.16 6.59 6.34 7.16 6.69 0.420
TP% 1.35 1.74 1.93 1.35 1.93 1.67 0.295
Figure 2 C/N ratio were ranging from 6.34 in January to 7.16.
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The pH values ranged between 6.82 (acidic) in February and 7.39 in January (neutral). The OM concentration was in the range of 30.44% (March)–37.43% (January). The contents of TN were ranging from 1.91% to 3.95 % and the contents of TP were ranged between
1.04% (March) and 1.71% (February). Records of C/N were ranging from 4.64 in March to 10.84 in February; this wide range is due to the difference of OC% contents (Table 3) (Figure 3).
pH 7.39 6.82 6.99 6.82 7.39 --- 0.292
OM% 37.43 35.79 30.44 30.44 37.43 34.55 3.655
OC% 21.71 20.72 17.55 17.55 21.71 19.99 2.173
TN% 2.08 1.91 3.95 1.91 3.95 2.64 1.131
C/N 10.43 10.84 4.46 4.46 10.84 8.57 3.591
TP% 1.21 1.71 1.04 1.04 1.71 1.32 0.348
Figure 3 Records of C/N were ranging from 4.64 in March to 10.84 in February.
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The pH values ranged values between 6.63 (acidic) in March and 6.97 (quite neutral) in January. The contents of TN ranged from 0.52 to 2.03%. The TP lowest value was 0.98% (March) and the highest
value was 1.97% (January). Records of C/N ratio ranged from 6.97 (February) to 15.07 (March) due to the difference of OC% contents (Table 4) (Figure 4).
pH 6.97 6.84 6.63 6.63 6.97 --- 0.171
OM% 20.12 45.26 13.25 13.25 45.26 26.21 16.851
OC% 11.64 26.25 7.84 7.84 26.25 15.24 0.719
TN% 1.67 2.03 0.52 0.52 2.03 1.4 0.988
C/N 6.97 12.93 15.07 6.97 15.07 11.65 4.197
TP% 1.97 1.82 0.98 0.98 1.97 1.59 0.533
Figure 4 Records of C/N ratio ranged from 6.97 (February) to 15.07 (March).
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The pH values ranged between 6.32 (acidic) in February and 7.27 (neutral) in January. The OM concentration ranged between17.83% (March) and 24.20% (February). The TN contents ranged between 2.99 and 4.17%. The TP contents were 0.97% (March) and 2.01%
(February). The C/N ratio were ranging from 2.47 (March) to 4.69 (February) due to a decrease in the TN% contents relative to an increase in the OC% contents (Table 5) (Figure 5).
pH 7.27 6.32 6.96 6.32 7.27 --- 0.484
OM% 21.89 24.2 17.83 17.83 24.2 21.3 3.224
OC% 12.67 14.04 10.34 10.34 14.04 12.35 1.87
TN% 3.07 2.99 4.17 2.99 4.17 3.41 0.659
C/N 4.12 4.69 2.47 2.47 4.69 3.76 1.152
TP% 1.06 2.01 0.97 0.97 2.01 1.34 0.576
Figure 5 The C/N ratio were ranging from 2.47 (March) to 4.69 (February).
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The pH values ranged between 6.51 (acidic) in March and 7.32 (slightly basic) in January. The OM contents ranged between 20.93% (January) and 23.9% (March). Contents of TN and TP were increasing during the study period, showing ranges of (2.78-4.57%) for TN and
(0.52-3.23%) for TP. For both, the highest values were obtained in March, while the lowest values were obtained in January. The C/N ratios were decreasing with range from 4.73 in January to 3.04 in March (Table 6) (Figure 6).
pH 7.32 6.87 6.51 6.51 7.32 --- 0.405
OM% 23.45 20.93 23.9 20.93 23.90 22.76 1.60
OC% 13.15 12.11 13.9 12.11 13.90 13.05 0.898
TN% 2.78 3.74 4.57 2.78 4.57 3.69 0.895
C/N 4.73 3.24 3.04 3.04 4.73 3.67 0.923
TP% 0.52 1.91 3.23 0.52 3.23 1.88 1.355
Figure 6 The C/N ratios were decreasing with range from 4.73 in January to 3.04 in March.
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The pH values ranged from 6.20 (acidic) in March to 7.39 (alkaline) in January may be due to wastewater composition. The OM contents decreased from 37.34 in January to 12.8 in March. Contents of each of TN and TP were highest in March with ranges (1.91-2.33%) for TN
and (1.21-1.92%) for TP. A wide range of the C/N ratio was recorded due to the different content of OC % reported. The differences in C/N ratios were ranging from 3.18 (March) to 10.43 (February) (Table 7) (Figure 7).
pH 7.39 6.82 6.20 6.20 7.39 --- 0.595
OM% 37.43 26.71 12.8 12.8 37.43 25.64 12.349
OC% 21.71 15.46 7.42 7.42 21.71 14.86 7.163
TN% 2.08 1.91 2.33 1.91 2.33 2.10 0.211
C/N 10.43 18.09 3.18 3.18 18.09 7.23 3.700
TP% 1.21 1.71 1.92 1.21 1.92 1.61 0.364
Figure 7 The differences in C/N ratios were ranging from 3.18 (March) to 10.43 (February).
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Values of pH ranged from 6.43 to 7.30, covering all of the slightly acidic, neutral state and slightly alkaline sides. This may be related to wastewater composition. The highest pH value was recorded in January, while the lowest value was recorded in February. The OM
content was increasing from 17.58% (January) to 28.07% (March). Contents of TN and TP showed average values of (2.67±0.25) for TN and (2.09±0.12) for TP. The C/N ratios were ranging from 4.81 to 5.80. (Table 8) (Figure 8)
pH 7.30 6.43 7.09 6.43 7.30 --- 0.453
OM% 17.54 23.71 28.07 17.54 28.07 23.10 5.290
OC% 13.57 13.75 16.28 13.57 16.28 14.53 1.513
TN% 2.82 2.37 2.82 2.37 2.82 2.67 0.259
C/N 4.81 5.8 5.77 4.81 5.80 5.46 0.563
TP% 2.21 1.97 2.10 1.97 2.21 2.09 0.12
Figure 8 The C/N ratios were ranging from 4.81 to 5.80.
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The highest value of pH was recorded in January (7.57) and the lowest value was recorded in March (6.93). The OM content ranged between 14.25% (January) and 18.57% (March). Contents of TN
showed values between 0.92% (March) and 2.18% (January). TP contents showed values between 0.59% (January) and 1.68% (March). The C/N ratios ranged between 3.78 and 11.77 (Table 9) (Figure 9).
Parameter Jan. Feb.…

Physicochemical characterization of the sewage sludge from guarchia wastewater treatment plant in benghazi-libya evaluation of the organic composition

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