Recovery phosphorus (P) from P-contaminated wastewater is an efficient and environmentally friendly mean to prevent water pollution and alleviate the P shortage crisis. In this study, oyster shell as calcium sources and peanut shells as carbon sources (mass ratio 1:1) were used to prepare a novel Ca-modified biochar (OBC) via co-pyrolysis, and its potential application after P adsorption as a P biofertilizer for soil was also investigated. The results shown that OBC had a remarkable P adsorption capacity from wastewater in a wide range of pH 4–12. The maximum P adsorption capacity of OBC was about 168.2 mg/g with adsorbent dosage 1 g/L, which was about 27.6 times that of the unmodified biochar. The adsorption isotherm and kinetic data were better described by Langmuir isotherm model (R² > 0.986) and the pseudo second-order model (R² > 0.975), respectively. Characterization analysis of OBC before and after P adsorption by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and specific surface area and porosity analyzer (BET) indicated that the remarkable P adsorption capacity of OBC was mainly ascribed to chemical precipitation, electrostatic adsorption, and hydrogen bonding. Pot experiment results showed that OBC after P adsorption could significantly promote the germination and growth of Spinacia, which manifested that OBC after P adsorption exhibited a good ability to be reused as P fertilizer for soil.

The biosorption of nickel(II) by dried cells of Bacillus cereus, isolated from the sediment from an SBR reactor, was studied by response surface methodology (RSM). In this study, RSM based on central composite rotatable design was used to analyze the combined and individual effects of operating parameters (biomass dose，initial concentration of nickel(II), and pH) on the nickel adsorption capacity by dried B. cereus at an ambient temperature. A quadratic polynomial equation was obtained which could predict the amount of adsorbed nickel(II) by dried B. cereus. The analysis of variance showed that the effects of pH and biomass dose both had a significant influence on the removal of nickel(II), but the effect of pH was the most significant. The maximum adsorption amount of nickel(II) was found at a pH of 4, biomass concentration of 2.0 g L⁻¹, and initial nickel(II) ion concentration of 150 mg L⁻¹. Under this condition, the maximum adsorption amount of nickel(II) and the maximum adsorption rate were 20.79 mg g⁻¹ and 41.44%, respectively. This study indicated that RSM was an effective method for optimizing the biosorption process. Dried B. cereus as an eco-friendly biosorbent showed a remarkable performance on the removal of nickel(II).

Iron as micronutrients is of great significance for forming a stable and efficient anaerobic digestion of food waste. Aim of this study was to examine the effect of iron supplementation on the mesophilic anaerobic digestion of food waste. Firstly, batch experiments were conducted with different iron concentration at a constant kitchen waste/inoculum ratio (K/I = 1.0), which indicated that the effect of iron on anaerobic digestion of was strictly dosage-dependent. Then, anaerobic digestion of food waste was conducted for 50 days in semi-continuous rectors with optimal iron concentration (2.0mg /L) under the same conditions. And the semi-continuous rectors obtained a good operation performance with low volatile fatty acids concentration, higher biogas production, high coenzyme F₄₂₀ and dehydrogenase concentrations. Furthermore, two samples taken on 7th day and 50th day were analyzed by high-throughput sequencing, which illustrated that the composition anaerobe community was stable. However, the growth and activity of several syntrophic microbial groups (Aminobacterium, Syntrophomonas, Anaerolineaceae, Methanosaeta, Methanosarcina, Methanobacterium and Methanospirillum), were stimulated by iron supplementation. The shift of microbial community suggested that a high-efficiency microbial community for methane production from food waste was formed by iron supplementation.