Hong-Liang Liu

Cadmium removal from simulated wastewater to biomass byproduct of Lentinus edodes

A kind of agricultural waste, the byproduct of brown-rot fungus Lentinus edodes, was used as an efficient biosorbent for the removal of cadmium from water in this paper. The sorption conditions, such as pH, the dose of biomass and the initial concentration of cadmium were examined. Three kinds of adsorption models were applied to simulate the biosorption data. Uptake of cadmium was higher in weak acid condition than in strong acid condition. Nearly no sorption of cadmium occurred when the pH value was lower than 2.5. Biosorption isothermal data could be well simulated by Freundlich model, and then Langmuir and Temkin model. Langmuir simulation of the biosorption showed that the maximum uptake of cadmium was 5.58mmol/g in weak acid condition, which was much higher than many other biosorbents. The exchanged proton was highly related to the uptake of cadmium in weak acid condition. Fourier transform infrared spectrums and energy-dispersive X-ray microanalyzer were used to reveal ion-exchange mechanism between cadmium and the functional groups or participated inorganic metal ions during biosorption.

Changes of microbial population structure related to lignin degradation during lignocellulosic waste composting

Microbial populations and their relationship to bioconversion during lignocellulosic waste composting were studied by quinone profiling. Nine quinones were observed in the initial composting materials, and 15 quinones were found in compost after 50days of composting. The quinone species Q-9(H2), Q-10 and Q-10(H2) which are indicative of certain fungi appeared at the thermophilic stage but disappeared at the cooling stage. Q-10, indicative of certain fungi, and MK-7, characteristic of certain bacteria, were the predominant quinones during the thermophilic stage and were correlated with lignin degradation at the thermophilic stage. The highest lignin degradation ratio (26%) and good cellulose degradation were found at the cooling stage and were correlated with quinones Q-9, MK-7 and long-chain menaquinones attributed to mesophilic fungi, bacteria and actinomycetes, respectively. The present findings will improve the understandings of microbial dynamics and roles in composting, which could provide useful references for development of composting technology.

A neural network predictive control system for paper mill wastewater treatment

Abstract This paper presents a neural network predictive control scheme for studying the coagulation process of wastewater treatment in a paper mill. A multi-layer back-propagation neural network is employed to model the nonlinear relationships between the removal rates of pollutants and the chemical dosages, in order to adapt the system to a variety of operating conditions and acquire a more flexible learning ability. The system includes a neural network emulator of the reaction process, a neural network controller, and an optimization procedure based on a performance function that is used to identify desired control inputs. The gradient descent algorithm method is used to realize the optimization procedure. The results indicate that reasonable forecasting and control performances have been achieved through the developed system.

Mycelial growth and solid-state fermentation of lignocellulosic waste by white-rot fungus Phanerochaete chrysosporium under lead stress

Lignocellulosic biomass is an abundant renewable resource difficult to degrade. Its bioconversion plays important roles in carbon cycles in nature, which may be influenced by heavy metals in environment. Mycelial growth and the degradation of lignocellulosic waste by lignin-degrading fungus Phanerochaete chrysosporium under lead stress were studied. It was shown that P. chrysosporium could grow in liquid media with 400 mg L⁻¹ Pb(II), and mycelial dry weight was reduced by 54% compared to the control. Yellow mycelia in irregular short-strip shape formed in Pb-containing media, whereas the control showed ivory-white regular mycelial pellets. Two possible responses to Pb stress were: dense hyphae, and secretion from mycelia to resist Pb. During solid-state fermentation of straw, fungal colonization capability under Pb stress was positively correlated with the removal efficiency of soluble-exchangeable Pb when its content was higher than 8.2 mg kg⁻¹ dry mass. Carboxymethyl cellulase activity and cellulose degradation were inhibited at different Pb concentrations, whereas low Pb concentrations increased xylanase and ligninolytic enzyme activities and the hemicellulose and lignin degradation. Cluster analyses indicated that Pb had similar effects on the different microbial indexes related to lignin and hemicellulose degradation. The present findings will advance the understandings of lignocellulose degradation by fungi under Pb pollution, which could provide useful references for developing metal-polluted waste biotreatment technology.

Form Distribution and Transformation of Pb in Composting of Pb-Polluted Lignocellulosic Waste with White-Rot Fungi

A major limitation of land application of compost is the potential heavy metal pollution, and lead (Pb) has been recognized as one of the most hazardous heavy metal. To reduce the hazards of Pb to the compost application, composting of Pb- polluted wastes by inoculating white-rot fungi was investigated. The parallel waste composting with no inoculants was performed as control. The form distribution and transformation of Pb during composting were discussed. Results showed that the active Pb ion was transformed into the inactive phase during composting. The soluble-exchangeable Pb with high toxicity in composting with white-rot fungi was reduced to 0 mg/kg dry weight compost at day 50, while that of the control only achieved 100.5 mg/kg till day 60. The higher content of organic-bound Pb (121.0 mg/kg) and residual Pb (141.9 mg/kg) with low toxicity was found after 60-day composting with white-rot fungi, compared to those in control. Meanwhile, the higher microbial biomass was observed in composting with white-rot fungi, and Pb concentrations correlated to the microbial biomass. All the results indicated that the method of composting with white-rot fungi reduced the transfer and bioavailability of Pb in compost so as to alleviate the potential stress of metal, and also improved the microbial growth.