Jianzhong Zheng

Nutrient transformation during aerobic composting of pig manure with biochar prepared at different temperatures

The effects of the corn stalk charred biomass (CB) prepared at different pyrolysis temperatures as additives on nutrient transformation during aerobic composting of pig manure were investigated. The results showed that the addition of CB carbonized at different temperatures to pig manure compost significantly influenced the compost temperature, moisture, pH, electrical conductivity, organic matter degradation, total nitrogen, and NH3 variations during composting. Compared with control and adding CB charred at lower temperature treatments, the addition of CB prepared over 700°C resulted in higher pH (over 9.2) and NH3 emission and lower potherb mustard seed germination index value during the thermophilic phase. Peak temperatures of composts appeared at 7 days for control and 11 days for CB added treatments. During 90 days composting, the organic matter degradation could be increased over 14.8–29.6% after adding of CB in the compost mixture. The introduction of CB in pig manure could prolong the thermophilic phase, inhibit moisture reduce, facilitate the organic matter decomposition, reduce diethylene triamine pentaacetic acid (DTPA) extractable Zn and Cu contents in pig manure composts and increase ryegrass growth. The study indicated that the corn stalk CB prepared around 500°C was a suitable additive in pig manure composting.

Organic bases in NAPLs and their impact on wettability

Abstract Organic bases in crude oil have been linked to complex interfacial phenomena that could affect the multiphase flow of these fluids in subsurface systems. Little information is available, however, to correlate the strength and concentration of organic bases in nonaqueous phase liquids (NAPLs) to interfacial properties. The specific objectives of this paper were: (1) to evaluate and apply titration techniques employing nonaqueous solvents to quantify the acid neutralizing capacity and characterize the strength of the organic base constituents in complex NAPL mixtures; and, (2) to relate these characteristics to the wetting properties of quartz minerals exposed to environmentally significant NAPLs. The selection of a suitable organic solvent is critical for nonaqueous titration. Mixtures of known organic bases were used to verify the capability of three different solvent systems for quantifying the concentration and strength of organic bases. Methyl iso-butyl ketone was identified as the best solvent for the nonaqueous titration—providing both accurate measurement of the total concentration of bases as well as providing a means of differentiating between strong and weak base constituents. The NAPLs tested showed a wide range of base concentrations and were found to contain only weak organic bases. All of the NAPLs with a base number greater than two significantly altered the system wettability at pH=4.6. Only a few, however affected the wettability at pH=7.2. These observations confirm the characterization of the organic bases as weak bases. The titration techniques, however, cannot characterize the strength of the bases precisely enough to predict the aqueous phase pH at which a NAPL–water–quartz system would become oil wetting.

Using flotation to separate oil spill contaminated beach sands.

Lab flotation in artificial sea water was used to separate sand-oil mixtures prepared by mixing crude oil with quartz-dominated beach sands. Major factors affecting the separation efficiency for three representative oils (light, waxy, and heavy viscous) were examined through lab flotation tests, vortex experiments, and oil viscosity measurements. Results showed that flotation in sea water can effectively separate the tested sand-oil mixtures which had large contrast in physicochemical properties: (1) aging of sand-oil mixtures reduced the separation efficiency; (2) both the viscosity of crude oil and its adhesion to sand surfaces had major impacts on separation efficiency; (3) addition of small amounts of surfactants could substantially improve the separation efficiency; and (4) for heavy viscous oil, hydrocarbon solvents needed to be added to improve separation because of their solvency and capability in reducing oil viscosity.

Bromide: A Pressing Issue to Address in China’s Shale Gas Extraction

C is fighting to shift its coal-based energy system to a clean and sustainable one to alleviate its ever increasing environmental pressures. Backed by the largest proven shale gas reserve worldwide, China has set an ambitious goal to produce 60−100 billion cubic meters of shale gas annually by 2020 by hydraulic cracking. Large amounts of shale gas wastewater (SGW) are expected to be generated in association with an average 700 gallons of brine produced per million cubic feet of gas produced, according to a recent analysis of data from Marcellus. Shale gas wastewater consists of flowback and produced water, a mixture of injected fluids for hydraulic fracturing and pore water from shale formation. Because of this, SGW often contains heavy metals, radioactive metals, high levels of total dissolved solids (TDS), and in some cases, elevated concentrations of bromide. Compared with other ions in water (e.g., heavy metals and radioactive ions), bromide does not readily adsorb on soils and sediments, and hence can migrate a long distance downstream once entering surface waters. At the dawn of massive production of shale gas, China should pay particular attention to this contaminant. Poor management of bromide-containing wastewater would potentially cause contamination of China’s already limited drinking water resources, and pose threats to the quality of the finished water from drinking water plants using the Br-contaminated source water due to the formation of carcinogenic brominated disinfection byproducts (DBPs) (Figure 1). Management strategies for SGW include underground injection, reuse in hydraulic fracturing, discharge to surface water after treatment, processing by evaporation ponds, and beneficial reuse outside of the industry. China’s shale gas exploration is presently at the stage of demonstrations mainly in Sichuan basin, and large scale commercial production is expected to start soon. Because of this, many environmental regulations and standards regarding SGW management (e.g., deep well injection, wastewater treatment and disposal) are lacking. As for infrastructure development in Sichuan basin, it would be a great challenge to develop, in limited time, a sufficient number of deep injection wells (similar to U.S. Class II wells) suitable for SGW disposal, considering the basin’s complex geology and the expensive cost in well drilling. In addition, SGW treatment plants need to be installed to treat the SGW that cannot be handled by other management approaches, and technologies for effective treatment and reuse of SGW still await to be developed. Based on the current status, it is concerned that, were SGW not properly managed at commercial production, partial discharge of SGW to surface waters might be inevitable. Discharge of effluents from SGW treatment facility to surface water is of particular concern for the water quality of the receiving water body, as elevated concentration of bromide has the risk to form DBPs (Figure 1). In the early stage of shale gas extraction in Marcellus, low availability of deep wells has led to surface discharge of treated produced water, causing elevated bromide concentrations in the receiving water body. In a study examining the impact of bromide discharge from one Marcellus wastewater treatment plant on the water quality of a receiving stream, Warner et al. found bromide was enriched almost by 40 folds even 1.78 km downstream from the discharge site, with the stream receiving as much as 136.6 tons of bromide annually from the treatment plant. In another study, elevated bromide concentrations in the Allegheny River has been linked to increased concentrations of brominated trihalomethanes in the finished water of Pittsburgh Water and Sewer Authority’s drinking water plants which draw raw water from this river. Further study suggested that the Marcellus Shale wastewater treatment facility was one of the major contributors of bromide in the raw water. Shale gas in China is mainly stored in Sichuan, Tarim, Junggar, and Songliao basins. Although the published bromide data on SGW is not available, useful information can still be extracted from the reported geochemical data of underground brine samples collected from oil and gas fields. Take Sichuan basin (holding china’s 40% shale gas reserve) for example, both its Lower Cambrian and the Upper Permian formations are

Adsorption of Pb(II) ions in aqueous solutions by common reed ash-derived SBA-15 modified by amino-silanes

AbstractAmino, di-amino, and tri-amino groups functionalized mesoporous silica (N-SBA-15, 2 N-SBA-15, and 3 N-SBA-15) were synthesized using reed ash as silica source. Batch experiments were conducted to investigate the impact of contact time, adsorbent dosage, solution pH, temperature, and concentration of Pb(II) ions onto SBA-15, N-SBA-15, 2 N-SBA-15, and 3 N-SBA-15. The results revealed that the overall adsorption process well fitted the pseudo-second-order kinetic model. The maximum adsorption capacity of N-SBA-15, 2 N-SBA-15, and 3 N-SBA-15 for Pb(II) was 108.16, 102.77, and 93.65 mg/g at 298 K, respectively. The adsorption capacities increased with the increase in temperatures and with the decrease in soluble salt concentrations. Thermodynamics analysis showed that the adsorptions of Pb(II) were feasible, spontaneous, and exothermic in nature. The capacity of the modified SBA-15 did not lose significantly after six adsorption–desorption cycles. The Pb(II) adsorption process was dominated by chemical...