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Fig. 5. Changes in NH4* and NO3~ during composting of food waste. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15% raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite.

Figure 5 Changes in NH4* and NO3~ during composting of food waste. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15% raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite.

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The analysis was made on dry weight basis except for moisture, pH, and EC. Physiochemical characteristics of food waste. Table 1
The analysis was made on dry weight basis except for moisture, pH, and EC. Physiochemical characteristics of food waste. Table 1
Fig. 1. Schematic diagram of in-vessel compost bioreactor. A laboratory scale in-vessel compost bioreactor made of plastic was used. The height and diameter of the reactor was 63.5 and 68.6cm respectively while the thickness of the vessel was 10 mm. The vessel was wrapped from outside with styrofoam and aluminum foil to
Fig. 1. Schematic diagram of in-vessel compost bioreactor. A laboratory scale in-vessel compost bioreactor made of plastic was used. The height and diameter of the reactor was 63.5 and 68.6cm respectively while the thickness of the vessel was 10 mm. The vessel was wrapped from outside with styrofoam and aluminum foil to
Comparison table for in-vessel composting experiments.
Comparison table for in-vessel composting experiments.
Chemical composition of the collected natural zeolite. Table 3
Chemical composition of the collected natural zeolite. Table 3
Fig. 2. Variation in temperature and moisture content during composting of food waste. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15 raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite. Thermophilic temperature phase for at least 1 week was critical for the efficient removal of pathogens and to produce hygienic compost (Chan et al., 2016). Strauch and Ballarini (1994) reported that when the temperature reached beyond 55°C, mostly all pathogens were de- stroyed. Furthermore, elevated temperature promoted degradation of the complex substrate to simpler components (He et al., 2013). Fig. 2a The thermophillic stage was maintained for more than three weeks, and afterward, it was progressively reduced to the mesophilic and cooling stage. It was observed that after 50 days no significant changes in temperature were recorded (Fig. 2a and b). Likewise, for the trials with 10% of zeolite concentration the maximum temperature (55.3 °C) was recorded for modified natural zeolite. However, this value for temperature was statistically like the raw natural zeolite (52°C). Si- milarly, for trial A the temperature was dropped drastically after 10 days and reached 36.7 °C after 30 days. The achieved thermophillic range was not enough to complete OM degradation and effective pa- thogens removal. The probable reason behind the lower temperature profile in trial A was the formation of organic acids during intensive degradation of easily available OM. In addition, there was no alkaline amendment to buffer the acidic environment thus resulted in a pH decrease and made the environment unfavorable for the microbial ac- tivities (Chan et al., 2016; Wagqas et al., 2018b). The high-water re- tention capacity of zeolite, due to high porosity, enabled them to cap- ture excess moisture and provided favorable aerobic conditions for faster O2 uptake to the degrading microbes (Jiwan et al., 2013). These conditions resulted in higher microbial activities to degrade OM
Fig. 2. Variation in temperature and moisture content during composting of food waste. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15 raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite. Thermophilic temperature phase for at least 1 week was critical for the efficient removal of pathogens and to produce hygienic compost (Chan et al., 2016). Strauch and Ballarini (1994) reported that when the temperature reached beyond 55°C, mostly all pathogens were de- stroyed. Furthermore, elevated temperature promoted degradation of the complex substrate to simpler components (He et al., 2013). Fig. 2a The thermophillic stage was maintained for more than three weeks, and afterward, it was progressively reduced to the mesophilic and cooling stage. It was observed that after 50 days no significant changes in temperature were recorded (Fig. 2a and b). Likewise, for the trials with 10% of zeolite concentration the maximum temperature (55.3 °C) was recorded for modified natural zeolite. However, this value for temperature was statistically like the raw natural zeolite (52°C). Si- milarly, for trial A the temperature was dropped drastically after 10 days and reached 36.7 °C after 30 days. The achieved thermophillic range was not enough to complete OM degradation and effective pa- thogens removal. The probable reason behind the lower temperature profile in trial A was the formation of organic acids during intensive degradation of easily available OM. In addition, there was no alkaline amendment to buffer the acidic environment thus resulted in a pH decrease and made the environment unfavorable for the microbial ac- tivities (Chan et al., 2016; Wagqas et al., 2018b). The high-water re- tention capacity of zeolite, due to high porosity, enabled them to cap- ture excess moisture and provided favorable aerobic conditions for faster O2 uptake to the degrading microbes (Jiwan et al., 2013). These conditions resulted in higher microbial activities to degrade OM
Statistical analysis for compost parameters. Table 4
Statistical analysis for compost parameters. Table 4
Fig. 3. Variation in pH and EC during composting of food waste. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15% raw natural zeolite Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite. Acidic pH was responsible for hindering the normal microbial ac- tivities and inhibited the degradation of the produced organic acids (Wang et al., 2013; Wagqas et al., 2017). Whereas, the trials amended with zeolites showed a remarkable variation in pH during the com- posting process. During the first week the pH was lowered, and after 10 days it reached 5.6 for trial B, 5.9 for trial C, 6 for trial D and 6.2 for trial E. Afterward, pH was increased and reached the peak value of 9.5 in trial E followed by trial C (9.1) after 30 days. The high pH value for the trials with high zeolite concentration (15%) was due to the high zeolite quantity, which posed a dilution effect and affected the pH of the composting mixture (Chan et al., 2016). Likewise, for trial B and C, the peak pH after 30 days was 7.9 and 7.1 respectively (Fig. 3a and b). After achieving the peak values, the pH was reduced and reached the optimum value of 6.5-8.0 required for a stable compost (Awasthi et al., 2016). The final compost pH was 7.5 for trial B, 8.0 for trial C, 7.7 for Fig. 3¢ and d illustrated the variation in EC during the composting process. EC measured the total ions concentration and described changes in the levels of inorganic ions such as Na*, $0.2, Kt, NO3, Cl~, and NH,* during the composting process (Zhang et al., 2014; Waagas et al., 2018b). High EC values represented excessive soluble salts and considered as detrimental to plant growth and development. During the composting process, the concentration of soluble salts was increased due to the degradation of complex OM. The statistical ana- lysis revealed that the zeolite type had non-significant effects, whereas their concentration and time duration had a significant effect on the EC of the compost. However, the combined interactions of zeolite types with concentrations and time duration also showed non-significant ef- fects towards EC (Table 5). Furthermore, Tukey's HSD test revealed high significant results for zeolite types and their concentration re- garding control trials (Table 5). EC of the food waste was 0.9mS cm? that was changed gradually with time during the composting process (Table 1). In trial A, a fluctuation was recorded where EC was increased gradually to 2mScm7~' after 20 days and then decreased to 1.5mScm~! after 30 days with least significant changes till 60 days (1.8 mS cm7!). Afterward, the EC was again increased to 2.2 mS cm?
Fig. 3. Variation in pH and EC during composting of food waste. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15% raw natural zeolite Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite. Acidic pH was responsible for hindering the normal microbial ac- tivities and inhibited the degradation of the produced organic acids (Wang et al., 2013; Wagqas et al., 2017). Whereas, the trials amended with zeolites showed a remarkable variation in pH during the com- posting process. During the first week the pH was lowered, and after 10 days it reached 5.6 for trial B, 5.9 for trial C, 6 for trial D and 6.2 for trial E. Afterward, pH was increased and reached the peak value of 9.5 in trial E followed by trial C (9.1) after 30 days. The high pH value for the trials with high zeolite concentration (15%) was due to the high zeolite quantity, which posed a dilution effect and affected the pH of the composting mixture (Chan et al., 2016). Likewise, for trial B and C, the peak pH after 30 days was 7.9 and 7.1 respectively (Fig. 3a and b). After achieving the peak values, the pH was reduced and reached the optimum value of 6.5-8.0 required for a stable compost (Awasthi et al., 2016). The final compost pH was 7.5 for trial B, 8.0 for trial C, 7.7 for Fig. 3¢ and d illustrated the variation in EC during the composting process. EC measured the total ions concentration and described changes in the levels of inorganic ions such as Na*, $0.2, Kt, NO3, Cl~, and NH,* during the composting process (Zhang et al., 2014; Waagas et al., 2018b). High EC values represented excessive soluble salts and considered as detrimental to plant growth and development. During the composting process, the concentration of soluble salts was increased due to the degradation of complex OM. The statistical ana- lysis revealed that the zeolite type had non-significant effects, whereas their concentration and time duration had a significant effect on the EC of the compost. However, the combined interactions of zeolite types with concentrations and time duration also showed non-significant ef- fects towards EC (Table 5). Furthermore, Tukey's HSD test revealed high significant results for zeolite types and their concentration re- garding control trials (Table 5). EC of the food waste was 0.9mS cm? that was changed gradually with time during the composting process (Table 1). In trial A, a fluctuation was recorded where EC was increased gradually to 2mScm7~' after 20 days and then decreased to 1.5mScm~! after 30 days with least significant changes till 60 days (1.8 mS cm7!). Afterward, the EC was again increased to 2.2 mS cm?
Physiochemical characteristics of compost after 90 days. Trial A: no zeolite amendment, Trial B: 10% raw zeolite, Trial C: 15% zeolite, Trial D: 10% modified zeolite, Trial E: 15% modified zeolite. Table 5
Physiochemical characteristics of compost after 90 days. Trial A: no zeolite amendment, Trial B: 10% raw zeolite, Trial C: 15% zeolite, Trial D: 10% modified zeolite, Trial E: 15% modified zeolite. Table 5
Fig. 4. Changes in OM, ash content and TC during composting of food waste. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15% raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite.
Fig. 4. Changes in OM, ash content and TC during composting of food waste. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15% raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite.
Fig. 6. Evolution in nitrification index (NI) during composting of food waste due to the addition of zeolite. Trial A: no zeolite amendment, Trial B: 10% raw naturé zeolite, Trial C: 15% raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite.
Fig. 6. Evolution in nitrification index (NI) during composting of food waste due to the addition of zeolite. Trial A: no zeolite amendment, Trial B: 10% raw naturé zeolite, Trial C: 15% raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite.
Fig. 7. Variation in germination index (GI) during composting of food waste because of zeolite addition. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15% raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite. The kinetics studies showed the maximum adsorption capacity of modified natural zeolite. Christidis et al. (2003) reported that thermal Fig. 5 (c,d) illustrated the changes in NO3 and showed that mi- neralization of food waste during the composting process increased the NO3 content in the end product. NO3 in the food waste was 20.3mgkg~/ that was increased with time in all experimental trials (Table 1 and Fig. 5). The trend observed in the current investigation was according to the general phenomenon that expects the ammonifi- cation process followed by the nitrification process. In the start of the experiment, the nitrification process was very slow, and it was observed
Fig. 7. Variation in germination index (GI) during composting of food waste because of zeolite addition. Trial A: no zeolite amendment, Trial B: 10% raw natural zeolite, Trial C: 15% raw natural zeolite, Trial D: 10% modified natural zeolite, Trial E: 15% modified natural zeolite. The kinetics studies showed the maximum adsorption capacity of modified natural zeolite. Christidis et al. (2003) reported that thermal Fig. 5 (c,d) illustrated the changes in NO3 and showed that mi- neralization of food waste during the composting process increased the NO3 content in the end product. NO3 in the food waste was 20.3mgkg~/ that was increased with time in all experimental trials (Table 1 and Fig. 5). The trend observed in the current investigation was according to the general phenomenon that expects the ammonifi- cation process followed by the nitrification process. In the start of the experiment, the nitrification process was very slow, and it was observed
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Environmental EngineeringEnvironmental ScienceSoil ScienceEnvironmental EducationEnvironmental StudiesEnvironmental SustainabilitySolid Waste ManagementEnvironmental Soil ScienceFood WasteNatural Zeolites
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