Xiaoyang Chen

Rapid production of maggots as feed supplement and organic fertilizer by the two-stage composting of pig manure.

A two-stage composting experiment was performed to utilize pig manure for producing maggots as feed supplement and organic fertilizer. Seven-day composting of 1.8 ton fresh manure inoculated with 9 kg mixture of housefly neonates and wheat bran produced 193 kg aging maggots, followed by 12 week composting to maturity. Reaching the thermophilic phase and final maturity faster was characteristic of the maggot-treated compost compared with the same-size natural compost. Upon the transit of the maggot-treated compost to the second stage, the composting temperature maintained around 55 °C for 9 days and the moisture decreased to ~40%. Moreover, higher pH, faster detoxification and different activity patterns for some microbial enzymes were observed. There was a strong material loss (35% water-soluble carbon and 16% total nitrogen) caused by the maggot culture in the first stage. Our results highlight a higher economic value of pig manure achieved through the two-stage composting without bulking agents.

Oxidation Degradation of Rhodamine B in Aqueous by Treatment System

The UV photolysis of persulfate () is a novel advanced oxidation technologies (AOTs), which leads to the formation of strong oxidizing radicals, sulfate radicals (). The effect of oxidant concentration, initial dye concentration, initial pH of solution, and various inorganic anions (, , and ) were investigated using Rhodamine B (RhB), a kind of xanthene dye, as a model pollutant. With the increase of oxidant , more produced to attack RhB molecules and result in the increase of RhB degradation. While the improvement was not sustained above a critical value, beyond which degradation rate does not increase. Initial pH of solution had great effect on the RhB degradation rate during system. is rather stable in acidic solutions, while increasing system pH results in the transformation of to •OH. The effects of three inorganic anions (, , and ) all had some negative effect on the degradation of RhB. Based on the RhB solution changes of the UV-vis absorption intensity during the treatment, decolorization of RhB accompanied the destruction of aromatic ring structures of RhB molecules.

Housefly maggot-treated composting as sustainable option for pig manure management

In traditional composting, large amounts of bulking agents must be added to reduce the moisture of pig manure, which increases the cost of composting and dilutes the N, P and K content in organic fertilizers. In this study, maggot treatment was used in composting instead of bulking agents. In experiment of selecting an optimal inoculum level for composting, the treatment of 0.5% maggot inoculum resulted in the maximum yield of late instar maggots, 11.6% (maggots weight/manure weight). The manure residue became noticeably granular by day 6 and its moisture content was below 60%, which was suitable for further composting without bulking agents. Moreover, in composting experiment with a natural compost without maggot inoculum and maggot-treated compost at 0.5% inoculum level, there were no significant differences in nutrient content between the two organic fertilizers from the two treatments (paired Students t15=1.0032, P=0.3317). Therefore, maggot culturing did not affect the characteristics of the organic fertilizer. The content of TNPK (total nitrogen+total phosphorus+total potassium) in organic fertilizer from maggot treatment was 10.72% (dry weight), which was far more than that of organic fertilizer made by conventional composting with bulking agents (about 8.0%). Dried maggots as feed meet the national standard (GB/T19164-2003) for commercial fish meal in China, which contained 55.32 ± 1.09% protein; 1.34 ± 0.02% methionine; 4.15 ± 0.10% lysine. This study highlights housefly maggot-treated composting can be considered sustainable alternatives for pig manure management to achieve high-quality organic fertilizer and maggots as feed without bulking agents.

Adsorptive removal of trace oxytetracycline from water by acid-modified zeolite: influencing factors

Because of the wide use of antibiotics in the livestock industry, trace tetracycline antibiotics are frequently detected in swine wastewater and water bodies near pig farms. Based on natural zeolite, modified zeolite was synthesized by treatment with nitric acid. As one kind of typical tetracyclines, oxytetracycline (OTC) was chosen as the target adsorbate. Removal of trace OTC by modified zeolite and the effects of several main water matrices on OTC adsorption were studied in detail. OTC removal efficiency by acid-modified zeolite was about 90%, compared to less than 20% by natural zeolite. In general, in acidic conditions the removal efficiency of OTC by modified zeolite was about 90%, which was much higher than 20-35% in alkaline conditions. An increase in ionic strength from 0.01 to 1.0 M led to a decrease in adsorption efficiency from 90 to 27%. The presence of 10.0 mg L(-1) dissolved humic acid accelerated sorption of OTC on modified zeolite, while 100.0 mg L(-1) humic acid resulted in the opposite effect. An increase in temperature contributed to enhancing the adsorption efficiency.

Analysis of volatile organic compounds in compost samples: A potential tool to determine appropriate composting time

Changes in volatile organic compound contents in compost samples during pig manure composting were studied using a headspace, solid-phase micro-extraction method (HS-SPME) followed by gas chromatography with mass spectrometric detection (GC/MS). Parameters affecting the SPME procedure were optimized as follows: the coating was carbon molecular sieve/polydimethylsiloxane (CAR/PDMS) fiber, the temperature was 60°C and the time was 30min. Under these conditions, 87 compounds were identified from 17 composting samples. Most of the volatile components could only be detected before day 22. However, benzenes, alkanes and alkenes increased and eventually stabilized after day 22. Phenol and acid substances, which are important factors for compost quality, were almost undetectable on day 39 in natural compost (NC) samples and on day 13 in maggot-treated compost (MC) samples. Our results indicate that the approach can be effectively used to determine the composting times by analysis of volatile substances in compost samples. An appropriate composting time not only ensures the quality of compost and reduces the loss of composting material but also reduces the generation of hazardous substances. The appropriate composting times for MC and NC were approximately 22days and 40days, respectively, during the summer in Zhejiang.

Preparation, characterisation and catalytic performance of paper mill sludge and municipal wastewater treatment sludge-based catalysts for Fenton-like oxidation of Rhodamine B

In this study, sludge-derived Fenton-like catalysts, namely potentially low cost, were successfully synthesized through a unique and original method, which was used to oxidative degradate Rhodamine B (RhB) as heterogeneous Fenton-like Fe/C catalysts. Two types of sludge sources were used as sludge-derived support carbon: paper mill sludge and municipal wastewater treatment sludge. This unique preparation method converted pyrolyzed sludge into a porous carbon-based carrier material by chemical activation and then used an iron loading impregnation method to synthesize the Fenton-like Fe/C catalyst. The prepared two types of catalysts including paper mill sludge-derived char-supported iron catalyst and municipal sewage sludge-derived char-supported iron catalyst were characterized in terms of Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and N2-adsorption/desorption. Compared with sludge-derived Fe/C catalyst without activation, both the PMSC-Fe and the MSSC-Fe catalyst exhibited much better catalytic performance in degrading RhB. Both PMSC-Fe and MSSC-Fe exhibited excellent catalytic stability and almost seldom Fe-ion leaching. A correlation could be found between surface area and RhB degradation, suggesting that surface area of the catalyst is an important factor for the catalytic performance. Two different sources of sludge also showed discrepancy in catalytic performance of RhB degradation, which is perhaps due to the different properties of the initial sewage sludge. The catalyst of PMSC-Fe and MSSC-Fe both has an excellent long-term stability. Possible degradation mechanism of RhB induced by sludge-derived Fe-C/H2O2 system is proposed.

Effect of aeration intensity on the nitrogen and phosphorus removal performance of membrane bioreactors

The ability of simultaneous phosphorus and nitrogen removal of sequencing batch membrane bioreactor (SBMBR) run in anaerobic/aerobic (AO) mode was examined under three aeration intensities (2.5, 3.75 and 5.0 m3(m2·h)-1). The results showed that the averaged removals of COD were over 90% at different aeration intensity. And the more aeration intensity was, the more ammonia nitrogen (NH4+) removal rate got. The removal rates of NH4+ under the three aeration intensities were 87.3%, 92.9% and 96.4%, respectively. Total nitrogen removal rate increased with the aeration intensity increasing, while excessive aeration intensity was disadvantageous to TN removal. The removal rates of TN under the three aeration intensities were 79.5%, 81.0% and 77.5%, respectively. Phosphorus release during anaerobic stage and uptake under aerobic/anoxic stage could be observed obviously in AO SBMBR system.