Sewage sludge is a good source of energetically desirable compounds and green algae in developing country like India. In this work, the combustion characteristics of sewage sludge and green algae are described. The calorific value (CV) of dried sewage sludge (n = 7) and green algae (n = 11) was ranged from 1800 to 6250 and 3700 to 6280 kcal/kg with mean value of 3999 ± 1347 and 4428 ± 547 kcal/kg, respectively. The effect of proximate variables and water quality parameters in the CV of sludge and algae are discussed.
Sewage sludge includes black and grey water and semi-solid precipitates released at the household levels. Total sewage generated from urban centres in India is »4.0 × 1010 L/day. The sewage sludge is a source of nutrients and pathogenic microbes. The sewage sludge is covered by the algal bloom in urban sectors of India. Algal bloom causes tastes and odors in the water. Some algae produce an aromatic odor resembling to that of particular flowers or vegetables. In addition, a spicy, a fishy odor and a grassy odor can also be produced by algae [
Raipur is a capital city of Chhattisgarh state of India, growing rapidly in unsustainable order due to being commercial center for steel, cement and forest products. At least two million habitants are living in this city over »1.0 × 103 km2 area by discharging »3.0 × 107 L/day waste water. They are dumped into seven open reservoirs constructed in the outer of city,
The composite water sample (100 × 5 mL from five points of each location) was collected into glass bottles (500-mL) in January 2016 as prescribed in the literature [
The physical parameters i.e. temperature (T), pH, electrical conductivity (EC), dissolved oxygen (DO) and reduction potential (RP) values of the water were measured at spot by Hanna made sensors. The total hardness (TH) and total alkalinity (TA) values of the filtered water were determined by the titration methods in the laboratory. The F− content of water was analyzed by using the Metrohm-720 ion selective electrode in the presence of the buffer. The content of ions i.e. Cl−,
The bulk density (BD) was measured by the water replacement method [
where, GCV, M, We, W1, W2 and ∆T represent gross calorific value of species (kcal/kg), water equivalent, weight of sample, weight of cotton thread, weight of fuse wire and rise in temperature, respectively.
The content of volatile compounds including moisture was analyzed by using a Metller thermogravimetric analyzer-TGA-2 at heating rate of 20˚C/min.
The value of non-volatile (fixed) carbon (FC) was computed by subtracting the fraction (%) of moisture (MC), volatile compounds (VCs) and ash residue (AR) to the 100.
Algae are main primary byproducts in all kinds of water bodies due to eutrophication, and being indicators of water pollution in a number of significant ways due to availability of contained nutrients. Algae are among the fastest-growing plants in the world and have much faster growth-rates than terrestrial crops. All sewage sludge reservoirs of country like India are floated with different types of algal blooms due to variations in the topology and exposure extent of sun light and nutrient levels.
The water quality of seven sewage reservoirs of Raipur city is shown in
All sewage sludge was colored with bad smell as shown in
S. No. | Location | Smell | Color | T, ˚C | pH | EC | RP | DO | Algal species in encountered |
---|---|---|---|---|---|---|---|---|---|
1 | Gudhiyari | Fishy | BG | 29 | 7.3 | 730 | 170 | 7.3 | Lyngbya spp., Phithophora spp. |
2 | Bhatagaon | Unpleasant | BBr | 28 | 6.6 | 824 | 150 | 7.4 | Microcystis spp. |
3 | Saddu Mowa | Unpleasant | BBr | 29 | 6.8 | 1120 | 120 | 6.5 | Phithophora spp. |
4 | Urla | Fishy | BG | 33 | 6.6 | 1543 | 90 | 5.9 | Microcystis spp., Hydrodictyon spp., Phithophora spp. |
5 | Siltara | Unpleasant | BG | 33 | 9.4 | 1380 | 100 | 7.2 | Hydrodictyon spp., Phithophora spp. |
6 | Heerapur | Fishy | BG | 30 | 6.6 | 1440 | 220 | 7.4 | Lyngbya spp. |
7 | Pachpedinaka | Rotten egg | BG | 28 | 7.1 | 720 | 110 | 7.2 | Phithophora spp. |
S. No. | F− | Cl− | Na+ | K+ | Fe | TH | TA | ||||
---|---|---|---|---|---|---|---|---|---|---|---|
1 | 1.6 | 71 | 40 | 490 | 4.5 | 13 | 90 | 27 | 0.3 | 250 | 340 |
2 | 0.9 | 60 | 22 | 510 | 5.4 | 10 | 156 | 39 | 0.4 | 270 | 470 |
3 | 1.2 | 54 | 51 | 610 | 8.1 | 9 | 132 | 33 | 0.5 | 360 | 568 |
4 | 1.2 | 84 | 48 | 690 | 8.4 | 8 | 167 | 70 | 0.6 | 320 | 720 |
5 | 1.4 | 53 | 56 | 680 | 7.8 | 13 | 149 | 65 | 0.5 | 340 | 624 |
6 | 1.0 | 66 | 31 | 690 | 7.2 | 7 | 158 | 57 | 0.4 | 310 | 412 |
7 | 1.7 | 48 | 38 | 570 | 5.1 | 13 | 101 | 32 | 0.4 | 240 | 403 |
S. No. | Location | Color | Smell | BD, kg/m3 | MC, % | CV, kcal/kg | AR, % |
---|---|---|---|---|---|---|---|
1 | Gudhiyari | LBr | Dirty | 830 | 4.6 | 1800 | 49 |
2 | Bhatagaon | LBr | Dirty | 870 | 3.5 | 2280 | 45 |
3 | SadduMowa | B | Dirty | 980 | 2.8 | 4920 | 43 |
4 | Urla | B | Dirty | 1050 | 2.4 | 6030 | 42 |
5 | Siltara | B | Dirty | 1080 | 2.1 | 6250 | 41 |
6 | Heerapur | DG | Dirty | 950 | 2.9 | 4120 | 44 |
7 | Pachpedinaka | BrB | Dirty | 880 | 3.9 | 2590 | 47 |
B = Black, BrB = Brownish black, LBr = Light brown, DG = Dark grey.
(MC), calorific value (CV) and ash residue (AR) of sewage sludge of seven reservoirs were ranged from 830 - 1080 kg/m3, 2.1% - 4.6%, 1800 - 6250 kcal/kg and 41% - 49% with mean value of 949 ± 94 kg/m3, 3.2% ± 0.9%, 3999 ± 1818 kcal/kg and 44% ± 2%, respectively. Among them, the highest calorific value of sludge located in the industrial area i.e. Siltara and Urla was observed, may be due to higher nutrient loading. The CV of the sludge was correlated well (r = 0.99) with the nutrient levels and BD unlikely to the MC and AR value,
The combustion characteristics of four algae i.e. hydrodictyon, lyngbya, microcystis, and phithophoragrown in seven reservoirs is shown in
The CV of the dried sewage sludge and algal biomass of the studied area was found to be comparable to other regions of the World [
F− | Cl− | Na+ | K+ | Fe | TH | TA | CV | |||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
F− | 1.00 | |||||||||||
Cl− | −0.25 | 1.00 | ||||||||||
0.42 | −0.03 | 1.00 | ||||||||||
−0.25 | 0.18 | 0.49 | 1.00 | |||||||||
−0.40 | 0.2 | 0.61 | 0.87 | 1.00 | ||||||||
0.80 | −0.47 | 0.22 | −0.50 | −0.58 | 1.00 | |||||||
Na+ | −0.82 | 0.32 | −0.04 | 0.66 | 0.71 | −0.71 | 1.00 | |||||
K+ | −0.35 | 0.42 | 0.33 | 0.86 | 0.73 | −0.41 | 0.80 | 1.00 | ||||
Fe | −0.26 | 0.24 | 0.58 | 0.73 | 0.88 | −0.42 | 0.67 | 0.71 | 1.00 | |||
TH | −0.42 | 0.03 | 0.62 | 0.70 | 0.93 | −0.47 | 0.67 | 0.53 | 0.72 | 1.00 | ||
TA | −0.26 | 0.27 | 0.62 | 0.65 | 0.85 | −0.31 | 0.67 | 0.73 | 0.97 | 0.73 | 1.00 | |
CV | −0.20 | 0.15 | 0.73 | 0.88 | 0.95 | −0.34 | 0.64 | 0.81 | 0.89 | 0.86 | 0.88 | 1.00 |
S. No. | Location | Algae | Color | Type of AB | BD, kg/m3 | MC, % | CV, kcal/kg | AR, % |
---|---|---|---|---|---|---|---|---|
1 | Gudhiyari | Lyngbya spp. | Gr | MF | 1010 | 2.1 | 6280 | 1.5 |
Gudhiyari | Phithophora spp. | Gr | MF | 920 | 4.2 | 3800 | 3.2 | |
2 | Bhatagaon | Microcystis spp. | BGr | SF | 930 | 4.3 | 3960 | 3.1 |
3 | SadduMowa | Phithophora spp. | Gr | MF | 910 | 4.5 | 3770 | 3.6 |
4 | Urla | Microcystis spp. | BGr | SF | 930 | 3.7 | 4070 | 2.8 |
Urla | Hydrodictyon spp. | Gr | MF | 1000 | 3.1 | 4100 | 2.1 | |
Urla | Phithophora spp. | Gr | MF | 920 | 3.1 | 3780 | 3.1 | |
5 | Siltara | Hydrodictyon spp. | Gr | MF | 1050 | 2.3 | 5250 | 2.6 |
Siltara | Phithophora spp. | Gr | MF | 920 | 4.6 | 3800 | 3.6 | |
6 | Heerapur | Lyngbya spp. | Gr | MF | 1070 | 1.5 | 6200 | 1.4 |
7 | Pachpedinaka | Phithophora spp. | Gr | MF | 930 | 3.7 | 3700 | 3.8 |
Gr = Green, BGr = Blue green, AB = Algal bloom, MF = Mate form, SF = Scum form.
The calorific value of the sewage sludge is found to be similar to biomass and animal waste. The heat value of the sludge and algae was found to be comparable. The heat value of algal boom is seemed to be independent of quality of the sludge because it is produced by process of eutrophication.
We are thankful to our University for providing equipment grant to the SOS in Environmental Science.
Yaman Kumar Sahu,Pravin Kumar Sahu,Suryakant Chakradhari,Khageshwar Singh Patel, (2016) Combustion Characteristics of Sewage Sludge and Algae. Natural Resources,07,205-213. doi: 10.4236/nr.2016.74019