Pyrolysis recycling of pig manure biochar adsorption material for decreasing ammonia nitrogen in biogas slurry

Exploration of ammonia stripping coupled adsorption-membrane filtration process for treating kitchen waste biogas slurry

The potential contamination of biogas slurry generated from the anaerobic digestion of kitchen waste (KW) poses a considerable challenge to its safe and effective utilization as a fertilizer. To tackle this problem, a novel route termed "AS-BC" was developed, integrating ammonia stripping (AS), biochar adsorption, and ceramic membrane filtration (CMF) for comprehensive pollutant mitigation. A stepwise optimization was carried out, comparing biochar adsorption investigation, the AS process, and the combined AS + CMF process. Results indicated that the AS process possessed the maximum total ammonia nitrogen (TAN) removal of 86.21% at an airflow rate of 40 L/min. The combined AS and CMF process with 0.1 μm membrane had best performance for total phosphorus (TP) with removal efficiencies of 80.45%-87.98%. Under the optimal biochar addition condition of 5 g/L with a particle size of 0.25-0.85 μm, the adsorption pretreatment effectively removed 0.41 g/g of soluble chemical oxygen demand (SCOD), prevented nutrient loss, and substantially enhanced pollutant removal efficiency in the subsequent CMF process. Compared to other routes, the route AS-BC achieved higher total nitrogen (TN), TAN, TP, and SCOD removal efficiency of 91.42%, 91.49%, 89.54%, and 76.34% from the raw biogas slurry, respectively. Moreover, the route AS-BC demonstrated its cost-effectiveness in producing nutrient-rich concentrated slurry suitable for use as fertilizer. The route AS-BC was proved to comprehensively remove various indicators from the KW biogas slurry while generating economically reuse by-products during the membrane filtration process. This study offers valuable insights into the trade-offs between AS performance enhancement and pollutant mitigation, pinpointing essential routes for future research and practical improvements.

Bifunctional system constructed by NiCu-F/DSA electrode self-coupling for efficient removal of ammonia nitrogen from landfill leachate

Landfill leachates containing high concentrations of ammonia nitrogen, due to its strong toxicity, large discharge and great environmental hazard, is in urgent need of efficient cleaning treatment. In this work, Ni1Cu0.25-F/DSA catalytic electrode was prepared via electrodeposition by means of fluorination-induced surface reconstruction. The surface of electrode was determined to be a porous sponge-like structure by physical characterizations. The electrode exhibited a superior ammonia oxidation reaction (AOR) activity and stability by a series of electrochemical tests. On this basis, a Ni1Cu0.25-F/DSA || Ni1Cu0.25-F/DSA bifunctional system was developed for efficient removal of ammonia nitrogen in landfill leachate. The results of denitrification experiment indicated that the removal efficiency of NH4+-N and TN were 99.89% and 68.9%, respectively, when the electrolytic cell potential was 1.7 V, pH was 13 and the initial ammonia concentration was 600 mg L-1. The NH4+-N removal efficiency remained above 95% after the cyclic denitrification experiment lasting for 6 days, which validates the robust stability of the electrode.

Role of cow dung and sawdust during the bioconversion of swine waste through the rotary drum composting process

The demand for strategic and environment-friendly swine waste (SW) management is critical in the northeastern states of India, which account for 46.7% of the country's total swine population. This paper examines nutrient-rich compost production from SW with minimal negative environmental fallout, using cow dung microbiological inoculum and sawdust bulking agent for expeditious rotary drum composting. Aerobic biodegradation conducted in a rotary drum composter (RDC), raised the feedstock temperature to > 40 °C in just 24 h, which stimulated thermophilic decomposition. The thermophilic phase remained for 16 days in the cow dung-amended 10:1:1 (swine waste:cow dung:sawdust) trial (RDC1) versus 7 days for the sawdust-amended 10:1 (swine waste:sawdust) trial (RDC2). After 20 days, the RDC1 product exhibited superior nutritional characteristics, with a total nitrogen content of 2.52%, a significantly reduced coliform population, and an overall weight loss of 25%. These findings highlight that incorporating cow dung (10% w/w) into SW and bulking agents through RDC produces high-quality compost in just 20 days. Thus, the livestock industry benefits significantly from this laboratory-scale method of improved waste management by producing valuable bioproducts via RDC.

Removal of environmental pollutants using biochar: current status and emerging opportunities

In recent times, biochar has emerged as a novel approach for environmental remediation due to its exceptional adsorption capacity, attributed to its porous structure formed by the pyrolysis of biomass at elevated temperatures in oxygen-restricted conditions. This characteristic has driven its widespread use in environmental remediation to remove pollutants. When biochar is introduced into ecosystems, it usually changes the makeup of microbial communities by offering a favorable habitat. Its porous structure creates a protective environment that shields them from external pressures. Consequently, microorganisms adhering to biochar surfaces exhibit increased resilience to environmental conditions, thereby enhancing their capacity to degrade pollutants. During this process, pollutants are broken down into smaller molecules through the collaborative efforts of biochar surface groups and microorganisms. Biochar is also often used in conjunction with composting techniques to enhance compost quality by improving aeration and serving as a carrier for slow-release fertilizers. The utilization of biochar to support sustainable agricultural practices and combat environmental contamination is a prominent area of current research. This study aims to examine the beneficial impacts of biochar application on the absorption and breakdown of contaminants in environmental and agricultural settings, offering insights into its optimization for enhanced efficacy.

Application of physicochemical techniques to the removal of ammonia nitrogen from water: a systematic review

Ammonia nitrogen is a common pollutant in water and soil, known for its biological toxicity and complex removal process. Traditional biological methods for removing ammonia nitrogen are often inefficient, especially under varying temperature conditions. This study reviews physicochemical techniques for the treatment and recovery of ammonia nitrogen from water. Key methods analyzed include ion exchange, adsorption, membrane separation, struvite precipitation, and advanced oxidation processes (AOPs). Findings indicate that these methods not only remove ammonia nitrogen but also allow for nitrogen recovery. Ion exchange, adsorption, and membrane separation are effective in separating ammonia nitrogen, while AOPs generate reactive species for efficient degradation. Struvite precipitation offers dual benefits of removal and resource recovery. Despite their advantages, these methods face challenges such as secondary pollution and high energy consumption. This paper highlights the development principles, current challenges, and future prospects of physicochemical techniques, emphasizing the need for integrated approaches to enhance ammonia nitrogen removal efficiency.

Efficient Adsorption of Nitrogen and Phosphorus in Wastewater by Biochar

Nitrogen and phosphorus play essential roles in ecosystems and organisms. However, with the development of industry and agriculture in recent years, excessive N and P have flowed into water bodies, leading to eutrophication, algal proliferation, and red tides, which are harmful to aquatic organisms. Biochar has a high specific surface area, abundant functional groups, and porous structure, which can effectively adsorb nitrogen and phosphorus in water, thus reducing environmental pollution, achieving the reusability of elements. This article provides an overview of the preparation of biochar, modification methods of biochar, advancements in the adsorption of nitrogen and phosphorus by biochar, factors influencing the adsorption of nitrogen and phosphorus in water by biochar, as well as reusability and adsorption mechanisms. Furthermore, the difficulties encountered and future research directions regarding the adsorption of nitrogen and phosphorus by biochar were proposed, providing references for the future application of biochar in nitrogen and phosphorus adsorption.

Evaluating the potential of biodegradation of swine manure through rotary drum composting utilizing different bulking agents

The rapid expansion of the pig industry and the concurrent increase in pig units have posed a significant waste management challenge, particularly in the form of piggery waste. In this study, the potential of three different bulking agents (sawdust, dry leaves, and rice straw) for the biodegradation of piggery waste was evaluated through rotary drum composting (RDC). Following the composting time of 20 days, evaluations of macro and micronutrient concentrations and the C/N ratio revealed stable, matured compost that could be used in farming. However, the saw dust amended RDC (RDC1) outperformed among the studied trails; the total nitrogen content of 1.54%, total phosphorus of 7.68 g kg-1, and total potassium of 23.45 g kg-1 demonstrated the bioproduct produced through RDC1 resulted in superior-quality end product achieved in only 20 days in comparison with other bulking agents studied. Further, the outcomes of the study can serve the swine livestock sector through effective bioconversion of the waste.