Assessments of the spatiotemporal distribution of livestock manure and its risk to the watershed are important to prevent water pollution. In this work, the spatiotemporal livestock manure distribution and its risk for the Chaohu lake basin were evaluated based on the excretion coefficient method and ArcGIS technology. In detail, the amounts of livestock manure and its associated pollutants, including chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD₅), ammonia (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP), were calculated from 2009 to 2019. Then, the diffusion concentrations of COD, BOD₅, NH₄⁺-N, TN, and TP and the water pollution risk index from livestock manure were estimated and predicted for the Chaohu lake basin. The results indicated that the mean amount of livestock manure had reached 1.04 × 10⁷ t in the Chaohu lake basin in the studied decade. The COD, BOD₅, NH₄⁺-N, TN, and TP from livestock manure in Feixi and Feidong contributed 54.26% and 54.40% of the total in the whole basin. These results demonstrate the potential pollution risk of livestock manure for the Chaohu lake basin. Moreover, the diffusion concentrations of COD, BOD₅, NH₄⁺-N, TN, and TP for the lake basin were from highest to lowest as follows: Feixi > Feidong > Chaohu > Lujiang > Wuwei > Shucheng > Hefei. The water pollution risk index was more than 20 in Feixi and Feidong, indicating that these areas were heavily affected by local livestock manure. The water pollution risk index will be approximately 18 for the Chaohu lake basin in 2030, implying that the Chaohu lake watershed will suffer moderate pollution from animal manure. These results provide scientific support for policymakers to enhance manure utilization efficiency and control livestock manure loss, causing water eutrophication in Chaohu lake basin or other similar watersheds.

Bioelectrochemical systems are widely used in waste utilization processes. Among them, anaerobic digestion (AD) and microbial electrolytic cell coupling (MEC) are cost-effective and efficient waste-to-energy technologies. In this study, the proposal was made that a carbon felt composite electrode plate be applied to an AD-MEC reactor. The control experiment was conducted using an AD reactor (without the external power supply). The result shows that the carbon felt composite electrode plate increased the biogas production of the AD-MEC reactor by 15.4%, and the average methane content increased by 9.49% compared to the control AD reactor. The total methane production of the AD-MEC reactor and control reactor was 302.51 and 407.79 mL, respectively. The total methane production of the AD-MEC reactor was 34.8% higher than the control group. In addition, the authors found that Methanosarcina and Methanosaeta activities in the AD-MEC reactor were significantly increased. The carbon felt composite electrode plate applied in AD-MEC may have promoted the methanogenic microorganisms’ interspecific acetic acid transport process and increased biogas production and methane content.

Nanosized calcium carbonate (NCC) plays a vital role in the rubber and plastic fields as a filler, but it cannot resolve the electrostatic problem. Humic-acid-based NCC (HA-NCC) was accidentally discovered in the reaction between biogas slurry and calcium chloride (CaCl₂), based on nutrient recovery and gradient treatment technology to solve the biogas slurry problem. A preliminary study on the preparation of conductive nanosized calcium carbonate (CNCC) from the HA-NCC was implemented. Meanwhile, a synchronous double decomposition coating method was proposed to properly explain the formation of HA-NCC in the biogas slurry. The CNCC was further obtained through drying and carbonizing the HA-NCC sample. The morphology of CNCC was a square shape with aggregation, and its crystals were calcite. The C content of CNCC was 5% higher than that of the normal CaCO₃, implying a synchronous coating effect of soluble HA in biogas slurry on NCC. The weight loss of CNCC was about 2.5% at 630 °C, explaining why the HA-NCC remained black at 550 °C for 4 h. The CNCC was partly ordered and graphitized. The resistivity of the CNCC reached 2.62 × 10⁶ Ω·cm. It could be used as a conductive powder. In view of the favorable characteristics described above, CNCC would be expected to be a filler and antistatic agent for plastics and rubbers to enhance the tensile and bending resistance of polymer materials, while eliminating electrostatic hazards. The results are also of great significance for developing high-end products to realize resource utilization of biogas slurry.

Undergraduate Water Quality Engineering courses rely on verification experiments lacking real engineering scenarios, limiting undergraduate participants’ comprehensive problem-solving skills. To remedy this issue, this study constructs an inquiry-oriented experiment using carbon-coated nano-calcium carbonate (C@CaCO₃) to enhance biological nitrification for digested wastewater with low alkalinity and high ammonia. It involves wastewater characterization, sequencing batch reactor (SBR) operation, quantification of chemical oxygen demand (COD), ammonium nitrogen (NH₄⁺-N) removal, mechanism discussion on alkalinity slow release and microbial carrier role of C@CaCO₃, and high-throughput analysis of microbial communities. Experimental results show that C@CaCO₃ increases NH₄⁺-N removal by 94.5 ± 4.8% in low-alkalinity water, while COD removal improves from 5.7 ± 3.0% to 29.5 ± 5.2%. These findings demonstrate that C@CaCO₃ effectively mitigates alkalinity limitation, facilitates microbial attachment, and promotes functional microbe enrichment, offering a practical solution for sustainable nitrogen management in nutrient-rich waste streams. Pedagogically, the case links water-quality monitoring, reactor control, and solid-waste resource recovery, enabling undergraduate participants to trace the full engineering workflow problem identification through quantitative design, operation, and mechanistic interpretation. Post-laboratory surveys and performance assessments indicate significant gains in experimental competence, data-analysis skills, and engineering judgment. By embedding a real-world, low-alkalinity wastewater challenge within the curriculum, the module advances sustainable water-resource management education and provides a replicable model for reforming laboratory teaching in Water Quality Engineering and related environmental-engineering courses.