90
3 Bio-augmented Composting of Organic Wastes in Villages and Towns
During the biological pre-treatment, the concentrations of VOCs generally
declined due to the utilization of microorganisms. As shown in Table 3.9, the detected
concentration of the total VOCs was 3.8091 mg/m
3 , which was 2.2 times lower than
that of primary wastes. Among 64 VOCs defined by using TO-14A and TO-15
methods of environmental protection agency (EPA) of the United States, 38 VOCs
were not detected. At the end of pre-treatment, ketone substances were found, which
indicated that alcohol, ketone, etc. were all generated due to the anaerobic reaction
occurring in local areas in the composting process.
3.3.4.3 Evaluation on the Treatment Effect of Deodorizing Technology
Using a Biofilter
By using a biofilter, the odorous gas generated in treatment plants of municipal
wastes during mechanical separation, biological pre-treatment and composting were
collected and removed. The change of concentration of pollutants before and after
removing odorous gas is shown in Table 3.10. The result showed that the biofilter
can favorably remove styrene and methyl sulfide, with the removal rate of 100%.
Moreover, the removal rates of NH 3 and H 2 S by using the biofilter were 38.10%
and 24.05%, respectively, and the removal rate (17.22%) of methyl mercaptan was
the lowest. It was probably that the temperature in summer rose and therefore gas
evaporated to thus take lots of moisture, further leading to the reduction of moisture
content of fillers. As a result, part of fillers is hardened to thus result in a low removal
rate of odorous gas. Therefore, it is necessary to increase moisture in filter materials
and it is necessary to maintain the moisture content of filter materials in the range of
55–65%.
3.4 Evaluation on Utilisability of Compost Products
3.4.1 Evaluation on Utilisability of Compost Products
of Kitchen Wastes
3.4.1.1 Germination Index
The toxicity test of plants is an effective and common method for evaluating the
maturity of compost, which mainly includes germination test, growth test and enzyme
activity, in which the seed germination experiment shows significant superiority.
Researchers generally suggested that if the germination index (GI) is in the range of
80–85%, the compost has been mature or shows no phytotoxicity, having a positive
effect on plant growth. By taking composting technology for rapid humification of
kitchen wastes as an example, after the composting lasted for 8 days, the GI of the
inoculated group was larger than 80% while that of the alkalified group was lower
3 Bio-augmented Composting of Organic Wastes in Villages and Towns
During the biological pre-treatment, the concentrations of VOCs generally
declined due to the utilization of microorganisms. As shown in Table 3.9, the detected
concentration of the total VOCs was 3.8091 mg/m
3 , which was 2.2 times lower than
that of primary wastes. Among 64 VOCs defined by using TO-14A and TO-15
methods of environmental protection agency (EPA) of the United States, 38 VOCs
were not detected. At the end of pre-treatment, ketone substances were found, which
indicated that alcohol, ketone, etc. were all generated due to the anaerobic reaction
occurring in local areas in the composting process.
3.3.4.3 Evaluation on the Treatment Effect of Deodorizing Technology
Using a Biofilter
By using a biofilter, the odorous gas generated in treatment plants of municipal
wastes during mechanical separation, biological pre-treatment and composting were
collected and removed. The change of concentration of pollutants before and after
removing odorous gas is shown in Table 3.10. The result showed that the biofilter
can favorably remove styrene and methyl sulfide, with the removal rate of 100%.
Moreover, the removal rates of NH 3 and H 2 S by using the biofilter were 38.10%
and 24.05%, respectively, and the removal rate (17.22%) of methyl mercaptan was
the lowest. It was probably that the temperature in summer rose and therefore gas
evaporated to thus take lots of moisture, further leading to the reduction of moisture
content of fillers. As a result, part of fillers is hardened to thus result in a low removal
rate of odorous gas. Therefore, it is necessary to increase moisture in filter materials
and it is necessary to maintain the moisture content of filter materials in the range of
55–65%.
3.4 Evaluation on Utilisability of Compost Products
3.4.1 Evaluation on Utilisability of Compost Products
of Kitchen Wastes
3.4.1.1 Germination Index
The toxicity test of plants is an effective and common method for evaluating the
maturity of compost, which mainly includes germination test, growth test and enzyme
activity, in which the seed germination experiment shows significant superiority.
Researchers generally suggested that if the germination index (GI) is in the range of
80–85%, the compost has been mature or shows no phytotoxicity, having a positive
effect on plant growth. By taking composting technology for rapid humification of
kitchen wastes as an example, after the composting lasted for 8 days, the GI of the
inoculated group was larger than 80% while that of the alkalified group was lower