PAPER • OPEN ACCESS
The effectiveness of coconut shell charcoal and activated carbon on deodorization of sludge from ice cream industry WWTP
To cite this article: H Ambarsari et al 2023 IOP Conf. Ser.: Earth Environ. Sci. 1201 012016
View the article online for updates and enhancements.
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The effectiveness of coconut shell charcoal and activated carbon on deodorization of sludge from ice cream industry WWTP
H Ambarsari1,*, T Suryati1, D H Akhadi1, S Herlina1, I Hanifah2, Hendrawati2, R Andriyani1, N A Gafur1 and S Suyanti1
1 Research Center for Environmental and Clean Technology, National Research and Innovation Agency, Building 820 Geostech, B.J. Habibie Science and Technology Center, South Tangerang City 15314, Banten, Indonesia
2 Department of Chemistry, Faculty of Science and Technology, UIN Syarif Hidayatullah, Jakarta, Indonesia
*E-mail: [email protected]; [email protected]
Abstract. Coconut shell contains several components of biomass including cellulose, lignin, and pentosan, which can be used in the form of charcoal as a bioabsorbent. Sludge waste is a residue formed as a by-product of wastewater treatment at a wastewater treatment plant (WWTP). which emits odors that can disturb local residents. This study aimed to deodorize ice cream slurry waste using coconut shell charcoal and activated carbon as the odor adsorbent. The ratio of each adsorbent and ice cream waste was based on the preliminary experiment, namely 1:1, 1:3, 1:5, 1:6, and 1:7. The measurement parameters for the sludge were odor value, pH, temperature, and water content which were measured daily. Ammonia and sulfide levels were measured using the titration method, while protein levels were determined using a UV-Vis spectrophotometer. Odor reduction in sludge waste mixed with activated carbon as the adsorbent was better than that with coconut shell charcoal; by which the optimum mass ratio was 1:3 with a decrease of 97.13% that was obtained within seven days. The ammonia levels in the sludge waste decreased from 10,276 mg/kg to 308 mg/kg by the use of coconut shell charcoal with a mass ratio of 1:1 and to 252 mg/kg by the use of activated carbon with a mass ratio of 1:1 at the end of the experiment. The sulfide content in the sludge waste decreased from 1.215 mg/L to 0.0483 mg/L in the sample with coconut shell charcoal as an adsorbent with a mass ratio of 1:1 and to 0.0483 mg/L in samples with activated carbon adsorbent ratio of 1:1 at the end of the experiment.
Keywords: activated carbon; coconut shell charcoal; deodorization; ice cream sludge waste
1. Introduction
Environmental pollution can be sourced from the ice cream industry and the resulting waste can be in the form of sludge. Sludge waste is one of the results of the waste handling process at the wastewater treatment plant (WWTP) where this waste emits an unpleasant odor from the sludge drying tub. The compounds contained in this sludge are generally more concentrated than liquid waste so it is more dangerous if directly disposed of in a landfill or the environment. Sludge waste that is not handled further and left exposed has the potential as a source of pollution. In addition to causing unpleasant odors, sludge waste that is exposed to rain will be followed by groundwater flow and enter the surrounding rivers [1].
Sludge from sewage treatment in the food industry mainly consists of organic materials such as carbohydrates, protein, fat, crude fiber, and water. These materials are easily degraded biologically and cause a foul odor that comes from the ammonia and hydrogen sulfide formed [2]. Several ways have been done to overcome the odor problem such as composting, landspreading, stockpiling, and other land injections. In another study, four companies investigated other processing methods namely anaerobic digestion, drying, composting and vermicomposting [3].
This research was conducted to find out a way to overcome the problem of odor caused by ice cream sludge waste. The odor elimination is needed to overcome the problem of pollution felt by the community around the waste processing industry and prevent expulsion by the surrounding community.
After deodorization, this waste can be used as a medium for growing maggots (Hermetia illucens) without making people around the waste processing industry uncomfortable. Utilization of this waste can help the economy of the surrounding community by using sludge waste as a medium for growing maggots, the results of which can be sold to fish farmers. Maggot cultivation using ice cream sludge waste has been previously carried out by Sulistia et al. in 2021, in which this waste was combined with manure and compost [4]. This combination resulted in black soldier fly maggots that were more in number and greater in size than the combination of compost and calcium with the sludge. Therefore, research on the biodeodorization of the ice cream sludge waste was carried out to remove odors in the waste in order to help the maggot cultivation process.
Ice cream industry sludge contains many nutrients, especially protein. The protein comes from the main ingredient for making ice cream, namely milk. Such milk-containing waste contains dissolved organic components at high concentrations including whey protein, lactose, fat, and minerals [5]. These components also give rise to odors from the decomposition of some compounds, resulting in, e.g., ammonia and hydrogen sulfide. Ice cream industry sludge contains 88.51 mg/L total Kjeldahl nitrogen, 98.7 mg/L sodium, 156.8 mg/L potassium, and 256.4 mg/L chloride [6].
According to Environmental Ministerial Decree No. 50/MenLH/II/1996 concerning Odor Level Standards [7], odor pollution is an unwanted odor at a certain level and time that can interfere with human health and environmental comfort. Ice cream sludge waste generates an unpleasant odor that can disturb and damage the quality of environmental air around the industrial area. The odor is caused by the content of organic materials such as carbohydrates, protein, fat, crude fiber, and water. These materials are easily biodegradable and cause environmental pollution, especially foul odors. The foul odor from this waste is mostly caused by the degradation of proteins into amino acids, including ammonia.
One of the ways to remove the odor in this sludge waste is by deodorizing it. This deodorization can be done biologically, physically or chemically. Physical removal of odor contaminants is mainly done through adsorption into the adsorbent. The most commonly used adsorbent in the wastewater industry is activated carbon, but zeolites have also been used as odor controllers [8]. Activated carbon has a high surface area per weight, which allows multiple active sites to absorb contaminants. In the gas phase, activated carbon is used for solvent recovery, removal of harmful substances from industrial exhaust, air quality control, and gas purification processes [9].
Previous research by Chasanah in 2019 could reduce the smell of milk sludge waste and also ammonia levels by using activated carbon from various types of dregs, e.g., coffee and Cavendish sunpride banana peels [10]. Using activated carbon at a ratio of 1:1 decreased odor from odor scale of 3 to 0 and ammonia levels were 31.97%, 39.42%, and 42.65% at contact times of 20, 40, and 60 minutes, respectively.
Pradana et al. in 2019 used activated carbon to reduce ammonia levels in domestic wastewater, where the average reduction in ammonia levels was 49.87% (20 minutes), 63.28% (40 minutes), and 75.46%
(60 minutes) [11]. Activated carbon was also used to reduce ammonia levels in tofu liquid waste at varying contact times of 1, 3, and 7 minutes to 6.5, 7.97, and 10.67 mg/L, respectively [12].
This study used self-made coconut shell charcoal and commercial activated carbon as adsorbents. In a previous study, coconut shells had been pre-treated and applied as activated charcoal for water purification and absorption of metals in the soil such as 0.1 mg/L Fe and 0.05 mg/L Mn, with a mixed
composition of activated carbon up to 35% [13]. Coconut shell charcoal has 97.44% carbon by mass as the main constituent element, while minor elements consist of sodium (Na) at 0.485%, magnesium (Mg) at 0.18%, aluminum (Al) at 0.09 %, chloride (Cl) at 0.47%, and potassium (K) at 1.06% [14].
This study aimed to compare the effectiveness of odor absorption between self-made coconut shell charcoal and commercial activated carbon. Sludge waste was mixed with coconut shell charcoal and activated carbon with various ratios of adsorbent to sludge, namely 1:1, 1:3, 1:5, 1:6, and 1:7. The test samples were analyzed for the level of odor, pH, and temperature for nine days at room temperature.
Testing of ammonia and sulfide levels was carried out on the early, middle, and end days by the titration method. The results of this study are expected to provide a solution to the odor problem in the ice cream industry caused by sludge waste, by utilizing coconut shell charcoal and commercial activated carbon at an affordable cost.
2. Material and Methods
2.1. Equipments
The equipments used in this study were porcelain dishes, oven, watch glass, filter paper, desiccator, 50 mL burette, vortex mixer, analytical balance, a set of distillation tools, 1 mL and 10 mL measuring pipettes, bulb, odormeter (Shinyei OMX-SRM), soil pH meter, universal pH indicator, dropper, thermometer, 250 mL beaker, 100 mL measuring cylinder, 10 mL and 100 mL volumetric flasks, test tube, 250 mL Erlenmeyer flask, container, cuvette, and UV-Vis spectrophotometer (Jasco V-530).
2.2. Materials
The materials used in the study were the sample of ice cream sludge waste from an ice cream industry WWTP, self-made coconut shell charcoal, commercial activated carbon, distilled water, 6 N HCl, 0.1 N NaOH, 6 N NaOH, 1% boric acid, 0.02 N H2SO4, aluminum foil, wrapping plastic, 0.0250 N iodine solution, starch indicator, 0.0250 N sodium thiosulfate, borate buffer, 1000 ppm stock solution of bovine serum albumin (BSA), sodium carbonate, CuSO4.5H2O, Na.K-tartrate, and Folin-Ciocalteu reagent.
Unprocessed coconut shell charcoal and commercial activated carbon were purchased from a shop in the Tangerang area, Banten Province, Indonesia. All chemicals used in this study were from Merck in analytical grade.
2.3. Experimental procedures
2.3.1. Adsorption process. The effluent sludge was measured for pH value, temperature, odor level, water content, and ammonia and sulfide levels before being mixed with the adsorbent. The adsorbents used in this study were coconut shell charcoal and activated carbon. Coconut shell charcoal was grounded using a mortar and sieved using a 90 μm (±170 mesh) sieve. Activated carbon was also sieved with a 90 μm sieve.
Table 1. Ratio of adsorbent and sludge.
Ratio (adsorbent:sludge)
Adsorbent mass (ABK or KA)
Sludge mass
1:1 5 g 5 g
1:3 5 g 15 g
1:5 5 g 25 g
1:6 5 g 30 g
1:7 5 g 35 g
Negative control - 5 g
Positive control 5 g -
Figure 1. Experimental design.
Preparation was done by making test samples, positive control, and negative control (Table 1). The test samples were the sample of sewage sludge which were mixed with the adsorbents in closed containers. The first set of test samples used coconut shell charcoal (coded as ABK) adsorbent, and the second set of test samples used activated carbon (coded as KA) adsorbent. The adsorbent:sludge ratios were 1:1, 1:3, 1:5, 1:6, and 1:7, with adsorbent mass (1 part) of 5 g and varying sludge mass. The mixtures of adsorbent and sludge in closed containers were shaken at the beginning of the mixing so that the adsorbents were evenly mixed with the sludge. The controls were made by only the waste sludge as the negative control and the adsorbent as the positive control.
Ice cream sludge
It was made as the negative
control Each adsorbent was mixed
with sludge with the ratio of 1:1, 1:3, 1:5, 1:6, dan 1:7 in
different containers Each was made
as the positive control
Daily (D0 up to D9) D0, D4, D9
Measurements of odor, temperature,
pH, and water content
Measurements of ammonia and sulfide
Negative control and samples (D9) Coconut shell
charcoal (ABK) and activated
carbon (KA)
Adsorption process
Measurement using UV-Vis spectrophotometer Measurement using
titration method
Perform initial analysis of pH, temperature, odor,
protein, ammonia and sulfide
Protein measurement Sample analysis
2.3.2. Odor Level Test. The test samples (ABK:S, KA:S), the negative controls, and the positive controls were measured for odor using an odormeter by inserting the tip of the sensor into the hole on the lid of the sample container and by pressing the sampling button for a few seconds. The odor value was observed on the displayed screen. Measurement of the odor of the sample was carried out from the first contact time (D0) to the ninth day (D9). Unfortunately, the measurement of odor in the sample was not carried out on D5 and D6 because it coincided with the end of the week and there were restrictions to using the laboratory due to the Covid-19 pandemic.
2.3.3. Temperature and pH test. The pH and temperature of the test samples (ABK:S, KA:S), the negative control, and the positive control were measured from D0 to D9. The pH was measured using a soil pH meter. Temperature measurements were performed using a thermometer that was touched to the ABK:S or KA:S samples in each container.
2.3.4. Water content test [15].Determination of the water content of the sample was carried out from D0 to D9. Measurement of water content in the sample was not carried out on D5 and D6 because it coincided with the end of the week and there were restrictions to use the laboratory due to the Covid-19 pandemic. The water content of the sample was determined by the gravimetric method, i.e. comparing the initial weight with the dry weight. The porcelain dish was heated in an oven at a temperature of 100°C–105°C for 30 minutes, then cooled in a desiccator and weighed. This method was repeated at an interval of 1 hour until a constant weight was obtained. A half gram (0.5 g) of the test sample was put into a porcelain dish and heated in an oven at a temperature of 105°C for 1 hour, cooled in a desiccator and weighed. After 1 hour, drying was repeated until a constant weight was obtained.
% water content=sample weight-dry weight
sample weight ×100% (1)
2.4. Measurement of protein content using the Lowry method
For spectrum determination, the cuvette was filled with standard protein solution at a concentration of 200 ppm, while the blank solution was prepared using distilled water. The absorbance of the solution was read in the wavelength range of 400-800 nm at 5 nm intervals. A wavelength relationship curve was then made precisely for the solution, then the regression coefficient was determined and used for further measurements.
The BSA stock solution with a concentration of 1000 ppm was prepared by weighing 50 mg of BSA powder and then dissolving it in 50 mL of distilled water. After that, dilutions were carried out to have a series of concentrations of 0, 40, 80, 120, 160, and 200 ppm. As much as 1 mL of BSA standard protein solutions of each concentration was put into test tubes. Lowry B reagent was prepared by mixing 100 mL of 2% Na2CO3 in 0.1 N NaOH with 1 mL of 1% CuSO4 solution and 2% NaK-tartrate solution [16].
Then, 5 mL of Lowry B reagent was added to each standard solution and left for 10 minutes, after which 0.5 mL of Folin-Ciocalteu reagent was also added, shaken, and left for 30 minutes. Their absorbances were then measured with the spectrophotometer, by which the calibration curve and r value were then calculated.
To determine the protein content of the sample, 0.25 g of the sample was dissolved in 100 mL of distilled water and then filtered. The sample was put into a test tube. Then, 5 mL of the Lowry B reagent was added to the sample solution and left for 10 minutes, after which 0.5 mL of Folin-Ciocalteu reagent was added and left for 30 minutes. The absorbance was measured with the spectrophotometer at the previously obtained wavelength.
2.5. Measurement of ammonia content [17]
The determination of ammonia in the test sample was conducted by distillation and titration methods.
The sludge samples were prepared by weighing about 1% wet sample or equivalent to 1 g dry weight for distillation. The residual chlorine in the sample was removed by the addition of dilute acid or dilute
base. If necessary, it was neutralized until it reached pH 7. The sample was added with 25 mL of borate buffer and 6 N NaOH until the pH reached 9.5.
The prepared sample was put in a Kjeldahl flask with distilled water and diluted to 250 mL. The sample was then distilled in the range of 6–10 mL/min with the end of the distillation tube put under the solution in the distillate holder. The distillate was collected as much as 100 mL in an Erlenmeyer containing 50 mL of 1% boric acid solution for titration, added with methyl red and methylene blue as indicators. Titration was carried out using standard 0.02 N sulfuric acid (H2SO4) titrant until the indicator changed color to pale lavender. The ammonia (NH3-N) content was calculated using the following equation:
NH3-N (mg/kg)=gram of sample dry weight(A-B)×280 (2) A = volume of H2SO4 sample titrant (mL)
B = volume of H2SO4 blank titrant (mL)
280 = molecular weight of 0.02 N H2SO4 standard solution
Determination of the effectivity of parameter reduction was expressed in the form of a percentage (%) with the following equation:
Effectivity (%) =(A0-Ai)×100%
A0 (3)
A0 = parameter levels before being treated Ai = parameter levels after being treated
2.6. Measurement of hydrogen sulfide content [18]
A 0.025 N iodine solution with a certain volume was measured and put in an Erlenmeyer flask. Mineral- free distilled water was added until the volume was 20 mL. Then, 2 mL of 6N HCl was added. The test sample (200 mL) was taken quantitatively and put into an Erlenmeyer flask with the tip of the pipette set below the surface of the solution. If the color of the iodine disappears, a solution of iodine was added until a light-yellow color appears. The volume of iodine used was then recorded.
The titration with 0.025 N sodium thiosulfate solution was performed by adding a few drops of starch indicator until a light-blue color was observed. After that, it was titrated again to the endpoint indicated by the disappearance of the light blue color. The sulfide (S2-) content was calculated using the following equation:
S2- (mg/L) =[(A×B)-(C×D)]×16000V ×VV2
1 (4)
A = volume of iodine solution (mL) B = normality of iodine solution
C = volume of sodium thiosulfate solution (mL) D = normality of sodium thiosulfate
V = volume of the test sample (mL) V2 = end volume (mL)
V1 = initial volume (mL) 3. Results and discussion
3.1. Results of odor measurement on samples
The odor level of the mixture of ice cream sludge waste with coconut shell charcoal as an adsorbent can be seen in Figure 2.
Figure 2 shows a graph of the decrease in odor level in the sample mixture of coconut shell charcoal and ice cream sludge waste (ABK:S). The odor level value unit was stated as ou/m3 (odor unit per cubic meter). Measurement of the odor at the initial contact between sludge waste and coconut shell charcoal was carried out after 30 minutes of contact. The odor level in all mixtures was stable from the seventh
day (D7) to the ninth day (D9), except for the 1:1 mixture that was stable from the fourth day (D4) to the ninth day (D9) with an odor value below 10 ou/m3.
Figure 2. The odor value of the mixture of coconut shell charcoal (ABK) and sludge waste at varying mass ratios.
Figure 3. The odor value of the mixture of activated carbon (KA) and sludge waste at varying mass ratios.
The value of the odor level in the mixture of ice cream sludge waste with activated carbon can be seen in Figure 3.Figure 3 shows the decrease of odor level in the sample mixture of activated carbon and sludge waste at each ratio. Measurements were made after the activated carbon and sludge waste were perfectly in contact, which was after 30 minutes. The average odor level for all ratios was stable
0 50 100 150 200 250 300 350
0 1 2 3 4 5 6 7 8 9 10
Odor value(ou/m3)
Contact time (Day)
ABK:S (1:1) ABK:S (1:3) ABK:S (1:5)
ABK:S (1:6) ABK:S (1:7) Sludge
Coconut Shell Charcoal
0 50 100 150 200 250 300 350
0 1 2 3 4 5 6 7 8 9 10
Odor value(ou/m3)
Contact time (Day)
KA:S (1:1) KA:S (1:3) KA:S (1:5)
KA:S (1:6) KA:S (1:7) Sludge
Activated Carbon
from D7 to D9, of which the ratio of 1:1 and 1:3 reached a value below 10 ou/m3. According to the standards in Pooja et al [19], the permissible odor concentration is 10 ou/m3. Samples that met this standard were those with a ratio of 1:1 for both samples and 1:3 for KA:S samples
Odor adsorption on activated carbon may occur due to the Van der Waals forces, where the attractive force is relatively weak between the adsorbate and the adsorbent surface [20]. The absence of covalent bonds between the adsorbent molecules and the adsorbate was what caused the odor level in the waste mixture to increase because it was easy to release the adsorbate from the surface of the adsorbent or it was reversible.
The functional groups found in coconut shell charcoal and activated carbon, which are non-polar molecules, could attract polar odorous compounds such as ammonia and hydrogen sulfide as well as non-polar compounds such as ketones and organic acids [9]. Ammonia and hydrogen sulfide molecules would be attracted into the cavities in the activated carbon so that the odor in the waste could decrease.
The best odor reduction with the addition of each adsorbent occurred in the sample with a mass ratio of 1:1. This result could be influenced by the amount of sludge waste mass that formed various odorous compounds, either in the form of single compounds such as ammonia and hydrogen sulfide or a combination of several compounds so that the more waste there was, the more odorous compounds were formed which could increase the odor value in the waste [21].
The decrease in odor calculated using Equation 3 when the ABK:S samples reached a stable odor from a ratio of 1:1, 1:3, 1:5, 1:6, and 1:7 was 96.8% (D4), 73.3% (D7), 66.4% (D7), 66.0% (D7), and 63.5% (D7), respectively. Meanwhile, the percentage of odor reduction in the KA:S sample from a ratio of 1:1, 1:3, 1:5, 1:6, and 1:7 was respectively 97.1% (D4), 95.6% (D7), 91.1% (D7), 85.6% (D8), and 74.0% (D7). The decrease in odor with the addition of coconut shell charcoal had a smaller percentage compared to the addition of activated charcoal. This might be due to the fact that the cavity in coconut shell charcoal was not as wide as in activated carbon because there were still hydrogen and hydrocarbon groups on the surface, so they could prevent the adsorbate from being absorbed [22].
The experimental results indicated that the optimum ratio for odor reduction between the two adsorbents in this ice cream waste was in the KA:S sample ratio of 1:3, in which the sludge waste used was more than the adsorbent and the odor value obtained from the KA:S sample with a 1:3 ratio was not much different from a 1:1 ratio. The length of time needed to reduce the odor in the waste was seven days. Previous research by Nugraha in 2020 showed that the odor decreased in the liquid waste of the dairy industry with the addition of Chlorella sp. from the initial odor of around 887-890 ou/m3 to reach 78 ou/m3 [23].
3.2. Results of pH measurement on samples
The ABK:S and KA:S samples were measured for their pH values using a soil pH meter from D0 to D9. Each sample was tested for pH value using a soil pH meter having a pH range between 5-8, while the negative control (untreated sludge waste) had a pH value of 8. The decrease in pH value can be seen in Figure 4 and Figure 5. Figure 4 shows the results of pH measurements on a mixture of coconut shell charcoal and sludge waste during the experiment from D0 to D9. The pH measurement results obtained did not experience significant changes. The pH results in these sample mixtures were between 6.5-8.
Figure 5 shows the results of pH measurements on the samples of activated carbon and sludge mixture during the experiment from D0 to D9. The most significant decrease in pH was seen in the ratio 1:6 and 1:7, in which the smallest pH of the two ratios was around 4. These samples had a pH in the range of 4-8.
According to the Regulation of the Minister of Environment, Republic of Indonesia Number 5 Year 2014 concerning Wastewater Quality Standards, the recommended pH parameter for dairy processing industry businesses/activities is between pH 6-9 [24]. The sludge sample waste from the ice cream industry collected prior to the experiment had a pH value of 8. The KA:S samples with a ratio of 1:6 and 1:7 had pH values below the quality standard, namely 5.6 and 5.9. The decrease in pH did not significantly affect the decrease in odor. The odor value in the KA:S sample with a ratio of 1:7 was greater than the other ratios but had a lower pH than the ratios of 1:1, 1:3 and 1:5.
Figure 4. ThepH values of coconut shell charcoal (ABK) and sludge mixture samples.
Figure 5. ThepH values of activated carbon (KA) and sludge mixture samples.
According to a previous study, this decrease in pH could be caused by the activity of bacteria that produced acidic compounds such as acetic acid, carbon dioxide and hydrogen [25]. This could also be caused by the occurrence of biochemical processes by converting the total dissolved sugars into organic acids [26]. In another previous study by Chasanah in 2019, the pH values without treatment and after treatment did not have a major effect because after adding activated carbon coffee grounds and banana peels, the sample had a pH between 6-7, while the milk sludge waste sample had a pH of 7 [10].
3.3. Results of temperature measurement on samples
The results of temperature measurements from D0 to D9 are shown in Figure 6 and Figure 7. Figure 6 shows that the temperature of each mixture ratio tended to fluctuate, ranging from 25.5-27.5oC during the measurements. The decrease in temperature occurred from D1 to D4. Then there was an increase in temperature on D7.
Figure 7 shows that the temperature of each mixture ratio tended to fluctuate between 25-28ºC. The decrease in temperature occurred on D1 to D3 and then increased on D4. According to Herawaty [20], this temperature change can be caused by the heat released during absorption. Adsorption occurs with the release of energy and generates heat (exothermic). Gas adsorption events occur very quickly when the adsorbent absorbs the adsorbate and forms an interaction between the two, then the energy release will occur and a higher temperature is obtained from the environment [20]. It is important to note that the above discussion is valid in most cases, especially for physical adsorption. However, there are few cases of chemical adsorption in which the bond dissociation energy of adsorbate molecules is greater than bond formation with the surface of the adsorbent, and thus results in net absorption of heat i.e.
0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 7 8 9
pH
Contact time (Day)
ABK:S (1:1) ABK:S (1:3) ABK:S (1:5) ABK:S (1:6) ABK:S (1:7)
0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 7 8 9
pH
Contact time (Day)
KA:S (1:1) KA:S (1:3) KA:S (1:5) KA:S (1:6) KA:S (1:7)
endothermic. This latter phenomenon could be seen on D1 until D4 when the temperatures were decreasing before increasing again on D5.
Figure 6. The temperatures of coconut shell charcoal (ABK) and sludge mixture samples.
Figure 7. The temperature of the activated carbon (KA) and sludge mixture samples.
In Chasanah's research of 2019 [10], the temperatures of the mixed samples of sludge waste with activated carbon of robusta coffee grounds, arabica, gayo aceh and banana peels were between 24.5- 27ºC measured on D3. Then the average temperature of the sample mixture increased on D7 with a maximum temperature of 27ºC [10].
3.4. Results of water content measurement
Figure 8 shows the water content of each ratio for the sample mixture of coconut shell charcoal and ice cream sludge waste from D0 to D9. The smallest water content was obtained by the sample with a ratio of 1:1 with a water content of 30%. The largest water content was obtained by a ratio of 1:7 with a water content of 60%. On D7 to D9 each ratio tended to be stable.
Figure 9 shows a graph of the water content value of each ratio in the sample mixture between activated carbon and ice cream sludge waste from D0 to D9. On the first day, samples with ratios of 1:1 and 1:3 experienced a decrease in water content while the water content at 1:6 and 1:7 ratios increased.
There was an increase in the percentage of water content in the sample with a ratio of 1:1 on D2 to D3
reaching 50%. From D7 to D9, the water content in each sample ratio looked stable and did not show a significant change.
23.5 24.5 25.5 26.5 27.5 28.5
0 1 2 3 4 7 8 9
Temperature(ºC)
Contact time (Day)
ABK:S (1:1) ABK:S (1:3) ABK:S (1:5) ABK:S (1:6) ABK:S (1:7)
23.5 24.5 25.5 26.5 27.5 28.5
0 1 2 3 4 7 8 9
Temperature (ºC)
Contact time (Day)
KA:S (1:1) KA:S (1:3) KA:S (1:5) KA:S (1:6) KA:S (1:7)
Figure 8. The water content of coconut shell charcoal (ABK) and sludge mixture samples.
Figure 9. The water content of activated carbon (KA) and sludge mixture samples.
The fluctuation of the water contents shown in Figure 8 and Figure 9 could happen due to the water vapor adsorption characteristic of each adsorbent material. Water vapor adsorption was found to be responsible for the diurnal fluctuations of the volumetric soil water content. This fluctuation was related to the adsorbent content, the depth and the initial water content of the adsorbent mixture [27]. Thus, it can be suggested that the graph of sludge only did not show any fluctuation over the period of measurement due to the lack of this water vapor adsorption characteristic.
High water content affects the odor generated by the sample [28]. The higher the water content in the sludge, the more pungent the odor produced. This is because water is a good medium for the growth of microorganisms so destructive microbes use the water contained in it to grow and break down substances contained in waste such as proteins that can produce odors. Furthermore, in a previous study it was found that in the utilization of sludge waste as a medium for maggot growth, the high water content in the medium was not optimal for maggot growth, because it would produce a low number of maggots caused by inhibition of maggot breeding in the media [29].
3.5. Protein content of the samples
Table 2 shows the concentration of protein content of the samples contained in untreated sludge and treated test samples. Measurement of protein content was conducted at the last contact time (D9). The
0 10 20 30 40 50 60 70 80 90
0 1 2 3 4 5 6 7 8 9 10
Water Content (%)
Contact time (Day)
ABK:S (1:1)
ABK:S (1:3)
ABK:S (1:5)
ABK:S (1:6)
ABK:S (1:7)
Sludge
0 10 20 30 40 50 60 70 80 90
0 1 2 3 4 5 6 7 8 9 10
Water Content (%)
Contact time (Day)
KA:S (1:1)
KA:S (1:3)
KA:S (1:5)
KA:S (1:6)
KA:S (1:7)
Sludge
results show that the percentage of dissolved protein in the sample ranged from 2.59–4.57% with the largest percentage found in the mixture of coconut shell charcoal and sludge (ABK: S) sample at a ratio of 1:6.
Table 2. Results of protein content analysis on samples.
Sample Protein concentration
(ppm) % Dissolved protein
1:1 ABK:S 75.14 3.01
1:1 KA:S 64.71 2.59
1:3 ABK:S 98.64 3.95
1:3 KA:S 77.86 3.11
1:5 ABK:S 92.71 3.71
1:5 KA:S 84.07 3.36
1:6 ABK:S 114.29 4.57
1:6 KA:S 107.79 4.31
1:7 ABK:S 112.71 4.51
1:7 KA:S 99.0 3.96
Sludge 93.21 3.73
The protein content of samples with the addition of activated carbon had smaller protein content than the samples with the addition of coconut shell charcoal. Activated carbon attracted proteins in the waste due to the electrostatic attraction between the negative charge on the activated carbon and the positive charge on the protein. In addition, hydrogen bonds would occur between the H amino and carboxyl groups in proteins with N and O on the activated carbon functional groups [30,31].
The protein contained in the sludge waste had a lower protein content than the sample. This result was maybe because microorganisms in sludge without adsorbent could produce proteolytic enzymes to break down high-molecular proteins into oligopeptides and free amino acids, which could also be used by microorganisms as energy. The mechanism of this reaction will produce water and the protein concentration will automatically decrease [32].
The protein content in the sludge sample could affect the odor value in the samples. When protein molecules decomposed, they would release particles called ketones and ammonia [33]. Protein breakdown by microorganisms also produces foul-smelling metabolites such as indole, cadeverin, organic acids, CO2, H2S, and sketol [34]. In previous research by Chasanah [10], the determination of the total N-content from the milk sludge waste obtained a total N-content of 0.05%. Furthermore, from the data in Table 2, it can be seen that the percentages of dissolved protein were almost the same for all treatments or were not significantly different than the sludge, hence it can be suggested that the odor produced was not only from the protein decomposition but also from other compounds' decomposition.
3.6. Ammonia content
The samples that were analyzed for ammonia content were samples with ratios of 1:1 and 1:3 from each adsorbent. The selection of these two ratios was based on the results of odor reduction, which gave a fairly good odor reduction. The contents of ammonia (NH3-N) in the samples for the ratios of 1:1 and 1:3 are shown in Figures 11 and 12.
The concentration of ammonia (NH3-N) in the ice cream sludge sample without contact with the adsorbent was 10,276 mg/kg. In Figure 10, the ammonia concentration in the ABK sample:S with the ratio of 1:1 at the beginning of the contact (D0) was 3,766 mg/kg, then there was a decrease in D4 (169 mg/kg) and increased again on D9 (308 mg/kg). While the ammonia concentration in the KA:S sample at D0 was 2,674 mg/kg, on D4 was 742 mg/kg and on D9 was 252 mg/kg. The decrease of ammonia concentration (NH3-N) in the ABK:S sample experienced a significant decrease in D4 but increased at the end of the contact time (D9). While the KA:S sample continued to decrease until D9. This shows that
the most optimum time for decreasing ammonia content in the sample was four days in the ABK:S sample and nine days for the KA:S sample.
Figure 10. Ammonia content in KA:S and ABK:S samples at a ratio of 1:1.
Figure 11. Ammonia content in KA:S and ABK:S samples at a ratio of 1:3.
Then in Figure 11, the ammonia concentration of the ABK:S and KA:S test samples with a ratio of 1:3, both experienced a significant decrease on D4. The increase in ammonia concentration occurred in the ABK:S sample on D9. The concentrations of ammonia (NH3-N) in the ABK sample:S ratio 1:3 at D0, D4, and D9 were 1,960 mg/kg, 224 mg/kg, and 1,512 mg/kg, respectively. Meanwhile, the ammonia concentrations of KA:S samples at D0, D4 and D9 were 2,184 mg/kg, 1,078 mg/kg, and 336 mg/kg, respectively. The optimum time to decrease ammonia concentration in the ABK:S sample at a 1:3 ratio was four days and in the KA:S sample at a 1:3 ratio was nine days.
Ammonia is one of the odor contributors that affect the odor in the sample. Ammonia compounds contained in the sample were absorbed by the adsorbent so that less ammonia was released into the air and reduced the odor generated by the sample. The quality standard of NH3-N in wastewater of business/dairy processing industry activities according to the Regulation of the Minister of the Environment of the Republic of Indonesia Number 5 of 2014 is 10 mg/L [23]. The level of ammonia obtained after the addition of the adsorbent exceeded the standard value for wastewater quality.
0 500 1000 1500 2000 2500 3000 3500 4000
0 4 9
Concentration(mg NH3-N/kg)
Contact time (Day)
ABK:S (1:1) KA:S (1:1)
0 500 1000 1500 2000 2500 3000 3500 4000
0 4 9
Concentration (mg NH3-N/kg)
Contact time (Day)
ABK:S (1:3) KA:S (1:3)
The percentage of ammonia (NH3-N) concentration reduction in the ABK:S sample with a ratio of 1:1 on D9 was 97%. Similarly, the percentage of ammonia reduction in the sample KA:S with a ratio of 1:1 on D9 was 97.6%. Then, at a ratio of 1:3, the percentage of ammonia reduction in the ABK:S sample was also greater than in the KA:S sample. The percentage of ammonia reduction in the ABK:S sample at a 1:3 ratio on D9 was 85.3%, while the percentage of ammonia reduction in the KA:S sample at a 1:3 ratio on D9 was 96.7%. This decrease in percentage that occurred during the experiment could be due to the adsorbent having been saturated in terms of time that exceeded the optimum limit [35]. In the study of Marhaini et al. in 2021, the decrease in ammonia contents occurred in petroleum wastewater from 379 mg/L to 265 mg/L after 30 hours or had an ammonia reduction efficiency value of 30.1% [36].
3.7. Hydrogen sulfide content
Sulfide content analysis was carried out using the iodometric titration method. The working principle of this method was the addition of excess iodine into the sample containing sulfide, the excess iodine was titrated back with sodium thiosulfate [17]. Tests were carried out on ABK:S and KA:S samples at ratios of 1:1 and 1:3 on the early (D0), middle (D4), and late (D9) samples. The sulfide content of each adsorbent is shown in Figures 13 and 14.
Figure 12. Sulfide content in KA:S and ABK:S samples at a ratio of 1:1.
Figure 13. Sulfide content in KA:S and ABK:S samples at a ratio of 1:3.
Analysis of the sulfide concentration in the sample of ice cream sludge waste without adsorbent was 1.21 mg S2-/L. Figure 12 shows the sulfide concentration of the two samples at a ratio of 1:1 which decreased quite well. Analysis of ABK:S samples with a ratio of 1:1 at D0 resulted in a sulfide content of 1.02 mg/L, then there was a significant sulfide decrease on D4 to 0.25 mg/L, and at D9 it was 0.048 mg/L. A significant decrease in sulfide concentration also occurred in the KA:S sample at D0, which was to a value of 0.25 mg/L. Then there was a small decrease in sulfide concentration on D4, which was 0.23 mg/L, and at D9 it was 0.05 mg/L.
0 0.2 0.4 0.6 0.8 1 1.2
0 4 9
Concentration(mgS2-/L)
Contact time (Day)
ABK:S (1:1) KA:S (1:1)
0 0.2 0.4 0.6 0.8 1 1.2
0 4 9
Concentration(mgS2-/L)
Contact time (day)
ABK:S (1:3) KA:S (1:3)
Figure 13 shows the sulfide concentration in the ABK:S and KA:S samples with a ratio of 1:3 to the contact time. The decrease in sulfide concentration in the ABK:S samples occurred at D0 and D4, respectively to 0.64 mg/L and 0.43 mg/L. Meanwhile, at the end of the contact time, there was no decrease or it was a fixed value. The decrease in sulfide concentration also occurred in the KA:S sample at D0, which was up to a value of 0.44 mg/L, while on D4 it had a value of 0.23 mg/L, and at the end of the contact time, it was 0.03 mg/L.
This decrease in hydrogen sulfide levels affected the odor in the sample so this compound also caused odor besides ammonia compounds. Then, the decrease in sulfide concentration on D4 was smaller than on D0. This was because the adsorbent had almost reached its saturation condition. This condition could occur when the pores on the surface of the adsorbent have been covered by adsorbed compounds such as ammonia and hydrogen sulfide contained in the sample so that subsequent absorption would be lower and finally the adsorbent cannot absorb the adsorbate [37].
The contact time required by activated carbon to absorb hydrogen sulfide in previous research by Loekitowati & Riyanti was eight days because at a contact time of more than eight days there was a decrease in the absorption of hydrogen sulfide, so it should be better to stop the absorption before the eighth day [38]. The functional group on activated carbon that plays a role in absorbing hydrogen sulfide is the hydroxyl group (-OH) where H2S is converted into S and water. This element of S was then adsorbed by activated carbon [39]. The level of hydrogen sulfide contained in petroleum liquid waste in the study of Marhaini et al in 2021 decreased from the initial concentration of 0.72 mg/L to 0.45 mg/L at 30 hours or decreased by 37.50% [36].
3.8. Overall parameter test results on samples
The samples had been tested on several parameters, namely odor, water content, temperature, pH, protein content, ammonia content, and hydrogen sulfide content. The overall results of parameter testing on the sample mixture of coconut shell charcoal with sludge and the sample mixture of activated carbon with sludge are presented and compared in Table 3.
Table 3. Overall parameter test results on samples.
Parameter ABK:S KA:S
1:1 1:3 1:5 1:6 1:7 1:1 1:3 1:5 1:6 1:7
Deodorization (%) 96.8 73.3 66.4 66.0 63.5 97.1 95.6 91.1 85.6 74.0 Water content (%) 37.5 53.8 57.5 55.0 66.3 37.5 51.3 57.5 67.5 60.0 Temperature (ºC) 26.4 26.4 26.5 26.7 26.7 26.6 26.7 26.6 26.8 27.1
pH 7.9 7.9 7.5 7.8 7.6 7.8 7.5 6.9 5.6 5.9
Protein (ppm) 75.1 98.6 92.7 114.3 112.7 64.7 77.9 84.1 107.8 99.0
NH3 (mg NH3/kg) 308 1.512 - - - 252 336 - - -
H2S (mgS2-/L) 0.048 0.427 - - - 0.048 0.032 - - - ABK:S = coconut shell charcoal:sludge
KA:S activated carbon:sludge (-) = no analysis
Based on the results in Table 3, samples of a mixture of activated carbon with sludge waste obtained better results compared to a mixture of coconut shell charcoal with sludge waste. It can be seen from the percentage of deodorization in the KA:S sample (% deodorization) where the results show the percentage was above 80%, hence the effectiveness level is very effective. Meanwhile, the ABK:S sample with a ratio of 1:3 only reached 73.3%, which is quite effective in reducing odor. The best percentage of odor reduction from each adsorbent was at the ratio of 1:3 in the KA:S sample. Based on the decrease in odor, the sludge waste added with activated carbon produced a better odor percentage value compared to the sludge waste added with coconut shell charcoal. This can be caused by the characteristics of the two adsorbents, where coconut shell charcoal has fewer pores because most of it is still covered by hydrogen, tar, and other organic compounds. Meanwhile, activated carbon has more
pores than coconut shell charcoal because it has gone through an activation process by heating or chemical process, which causes the decomposition process of organic compounds so that the absorption of odors in activated carbon produces a greater percentage reduction than coconut shell charcoal [40,41].
The physical changes observed during the experiment were water content, temperature and pH. The water content decreased after being treated, which was previously 80% as shown in Table 5. This change in water content caused the texture of the sludge waste to be harder than the previous one. The temperature of the sludge waste during the experiment did not change much before being treated or after being treated. The decrease in pH that occurred during the experiment was not too different from the pH of the untreated waste sample. Significant changes in pH only occurred in the sample KA:S ratio 1:6 and 1:7.
The decrease in ammonia concentration occurred quite large from an ammonia concentration of 10,276 mg/kg in untreated sludge waste. Ammonia formation was the result of protein decomposition into amino acids by bacteria. Likewise, the decrease in hydrogen sulfide concentration occurred in the sludge waste, which had an initial concentration of 1.2149 mg/L. Hydrogen sulfide is a compound that is usually formed in the decay of organic substances caused by bacteria [42].
4. Conclusion
Based on the data obtained from the results of the analysis and testing of coconut shell charcoal and activated carbon on the deodorization of ice cream sludge waste, it can be concluded that the largest percentage of effectiveness in reducing odor by coconut shell charcoal was 96.8%, while by activated carbon was 97.1%. The optimum ratio for the deodorization process was with the addition of activated carbon adsorbent at a ratio of 1:3 with a duration of seven days since it could process more amounts of sludge with the same amount of adsorbent than the ratio of 1:1. The ammonia and sulfide levels in the sample with the addition of activated carbon were smaller than those with the addition of coconut shell charcoal on the ninth day. The protein content decreased after the deodorization process with the protein concentration in the sample added with activated carbon was smaller than with coconut shell charcoal.
Acknowledgments
This research was fully funded by the research grant of PPTI (Development and Application of Industrial Technology) Program administered by Indonesia State Ministry of Resarch, Technology, and Higher Education Financial Year 2019 – 2020 and using the laboratory facilities of Indonesia Agency for The Assessment and Application of Technology (BPPT, Agency for the Assessment and Application of Technology). Special thanks to all technical and laboratory assistants as well as the field research partners from PT Siklus Mutiara Nusantara (PT SMN).
Author contributions
All authors contributed equally as the main contributors of this paper from the sampling, experimental design, primary and secondary data acquisition, data analysis and paper composition. All authors read and approved the final paper.
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