A novel additional carbon source derived from rotten fruits: Application for the denitrification from mature landfill leachate and evaluation the economic benefits

Deciphering nitrogen removal performance concerning heterotrophic microorganism's succession by using three typical acid-rich fermentation liquids of food waste as carbon sources in high ammonium and high salt wastewater treatment

Understanding the performance and microbial succession in nitrogen removal using fermentation liquid as carbon source can provide a practical basis for treating low C/N ratio wastewater. In this study, three typical fermentation liquids of food waste (FW) enriched with lactic acid (LA), propionic acid (PA), and butyric acid (BA) were added to high ammonia and high salt (HAHS) wastewater treatment process. Results showed that effluent TN decreased from 50 mg/L to around 15 mg/L with the influent concentration around 1000 mg/L after adding fermentation liquid enriched with LA and PA. In contrast, adding BA-rich fermentation liquid gradually deteriorated the nitrogen removal due to the nitrification process being impaired. Genus Thauera predominated in HAHS wastewater system via heterotrophic simultaneous nitrification and denitrification (SND) process. Utilization of LA- and PA-rich fermentation liquids induced the acclimation of other heterotrophic SND microbes and partially replaced Thauera. Conversely, BA-rich carbon source promoted the proliferation of heterotrophic denitrifying and ordinary heterotrophic microorganisms, thereby inhibiting nitrification process and ultimately leading to the failure of nitrogen removal. Meanwhile, the relative abundance of denitrification genes, including napAB, nirKS, norBC, and NosZ, annotated in Thauera exhibited the lowest relative abundance in BA-rich phase. This study provides valuable insights into the mechanism of using FW fermentation liquid as an alternative carbon source to promote nitrogen removal in HAHS wastewater.

Optimizing total ammonia-nitrogen concentration for enhanced microbial fuel cell performance in landfill leachate treatment: a bibliometric analysis and future directions

Untreated landfill leachate can harm the environment and human health due to its organic debris, heavy metals, and nitrogen molecules like ammonia. Microbial fuel cells (MFCs) have emerged as a promising technology for treating landfill leachate and generating energy. However, high concentrations of total ammonia-nitrogen (TAN), which includes both ammonia and the ammonium ion, can impede MFC performance. Therefore, maintaining an adequate TAN concentration is crucial, as both excess and insufficient levels can reduce power generation. To evaluate the worldwide research on MFCs using landfill leachate as a substrate, bibliometric analysis was conducted to assess publication output, author-country co-authorship, and author keyword co-occurrence. Scopus and Web of Science retrieved 98 journal articles on this topic during 2011-2022; 18 were specifically evaluated and analysed for MFC ammonia inhibition. The results showed that research on MFC using landfill leachate as a substrate began in 2011, and the number of related papers has consistently increased every 2 years, totaling 4060 references. China, India, and the USA accounted for approximately 60% of all global publications, while the remaining 40% was contributed by 70 other countries/territories. Chongqing University emerged as one of the top contributors among this subject's ten most productive universities. Most studies found that maintaining TAN concentrations in the 400-800 mg L-1 in MFC operation produced good power density, pollution elimination, and microbial acclimatization. However, the database has few articles on MFC and landfill leachate; MFC ammonia inhibition remains the main factor impacting system performance. This bibliographic analysis provides excellent references and future research directions, highlighting the current limitations of MFC research in this area.

Comparative insight into the effects of different carbon source supplement on antibiotic resistance genes during whole-run and short-cut nitrification-denitrification processes

Mature landfill leachate is known for nitrogen-removal challenging and meantime was considered as an important sink of antibiotic resistance genes (ARGs). The added external carbon sources, enabling the short-cut nitrification and denitrification, may facilitate the proliferation of bacteria that possibly carry ARGs. However, this speculation has yet to be studied. Here, we explored the effects of glucose, sodium acetate, and methanol supplements on ARGs during whole-run and short-cut treatment processes. The results showed that sodium acetate supplement during short-cut process efficiently reduced the abundances of total ARGs (0.84-1.99 copies/16S rRNA) and integrons (0.59-1.20 copies/16S rRNA), which were highly enhanced by methanol addition during whole-run treatment process (total ARGs: 3.60-11.01 copies/16S rRNA, integrons: 1.20-4.69 copies/16S rRNA). Indirect gradient analysis showed that the variation of ARGs was not correlated with the supplement of different external carbon source. Correlation analysis indicated that dominant intl1 (55.99 ± 17.61% of integrons) showed positively significant correlations with all detected ARGs expect for sul2 and ermB (p < 0.05), suggesting the significant role on ARGs dissemination. Redundancy analysis illustrated that the potential hosts of intl1, intl2, sul1, tetQ, tetM, mefA, and mexF were dominant Bacteroidetes and Actinobacteria. Interestingly, the numbers and significant extent of correlations under the supplement of sodium acetate during short-cut denitrification process were obviously declined, and it was in accordance with ARGs reduced by sodium acetate supplement, suggesting sodium acetate displayed the efficient ARGs reduction during short-cut process. In summary, this study provides a comparative understanding of the effects on ARGs by different carbon source supplements during nitrification-denitrification processes of leachate; sodium acetate is the optimal carbon source.

Waste reclamation from municipal solid waste for the cost-efficient treatment of landfill leachate with a novel biological trickle reactor system

Mature landfill leachate (MLL) would be a tough nut to crack, how to realize waste reclamation while deal with the intractable by-products deserves for more considerations. In this study, a novel system, equipped with two biological trickle reactors developed by inert wastes and a connected organic feeder using waste-recycling rotten banana powder, was established for treating MLL. Results indicated that superior pollutant removal performance and long-term stability were achieved by this system, with only COD and TN concentrations slightly higher than the relevant standard limits. But the shortage about poor resistance to shock pollution loads, was underlined by the fluctuation of water quality. Anaerobic condition and carbon source supplementation contributed to more microbial similarities but less community richness and diversity among inert fillings, and the selective enrichment of denitrification and organic-degrading strains simultaneously occurred. The comparisons with common processes demonstrated that this system was a cost-efficient choice for MLL treatment.

Waste-derived volatile fatty acid production and ammonium removal from it by ion exchange process with natural zeolite

Volatile fatty acids (VFAs) produced during anaerobic digestion (AD) of organic waste are a promising alternative carbon source for various biological processes; however, their applications are limited due to the presence of impurities such as ammonium (NH₄⁺). This study investigates the potential for removal of ammonium using a naturally occurring zeolite (clinoptilolite) from chicken manure (CKM) derived VFA effluent recovered from an anaerobic membrane bioreactor (MBR). Experiments were conducted for both synthetic and actual VFA (AD-VFA) solutions, and the effects of different parameters were investigated with batch and continuous studies. It was observed that the Langmuir-type isotherm provided the best fit to the equilibrium data in the isotherm investigations carried out with the AD-VFA solution. The maximum adsorption capacity (q_m) was found as 15.7 mg NH₄⁺/g clinoptilolite. The effect of some operational parameters on process performance such as pH, initial NH₄⁺ loading and potassium ion (K⁺) concentration was investigated. The pH had a negligible effect on ammonium removal for a pH range of 3-7, while the removal efficiency of ammonium decreased with the increase of initial NH₄⁺ loading and K⁺ concentration. At the optimum conditions determined in batch experiments, the ammonium removal from synthetic and AD-VFA solutions were compared and average ammonium removal efficiencies of 93 and 94% were found in 12 h equilibrium time for synthetic and AD-VFA solutions, respectively. Overall findings indicated that clinoptilolite has excellent potential for ion exchange when combined with biological processes such as acidogenic fermentation of VFAs to purify the solution from high-ammonium content.

Effects of biochar on water quality and rice productivity under straw returning condition in a rice-wheat rotation region

Straw returning is helpful to improve soil properties and realize the reutilization of agricultural waste. However, wheat straw returning may result in paddy water quality deterioration in rice-wheat rotation regions. This study conducted pot experiments of rice planting with different biochar application rates (0, 5, 20, and 40 t/hm²) under wheat straw returning conditions. The purposes are to investigate the applicability of biochar mixed with wheat straw returning to paddy fields and explore the effects of biochar on water quality, leaching losses of nitrogen (N) and phosphorus (P), and rice yield components. Results indicated that total straw returning reduced the water quality in paddy surface water and aggravated the leaching losses of N and P. Fortunately, the biochar application improved the negative effects caused by straw returning. 40 t/hm² biochar mixed with straw returning significantly reduced the concentrations of COD and N in paddy surface water and N leaching loss than straw returning treatment (ST), decreased by 48.33%, 41.01%, and 45.73%, respectively. Meanwhile, applying biochar at a rate of 20 t/hm² with straw returning is suitable to control the diffusion of P. In addition, the ST treatment had no significant effect on rice yield, while the proper application rate of biochar under straw returning condition can improve rice yield and promote N utilization. 20 t/hm² biochar treatment is more effective to improving rice yield (16.89%) and N use efficiency (NUE) (10.14%). These findings can provide a new method to solve the negative effects of total straw returning on the water environment and rice growth and guide the utilization of straw resources in the rice-wheat rotation regions.

A novel waste-recycled chelating agent for the stabilization of lead in municipal solid waste incineration fly ash: Preparation, feasibility, and mechanism analysis

There are two key issues in the area of waste management: one is stabilizing heavy metal, lead (Pb), in municipal solid waste incineration fly ash (MSWI-FA), the other is enhancing nitrogen utilization efficiency from organic waste. However, the connection between both issues was limited. In this study, a novel organic chelating agent based on food waste, FW-CA, was produced for immobilizing Pb. A maximum 86.22% of polypeptide in hydrolysis liquid of FW was utilized for preparing FW-CA with a yield of 8.22 g/L. Results indicated that FW-CA-stabilized fly ash satisfied the criteria of GB 18598-2019 with a dosage of 4.6%, lower than the demand of pure chemicals and industrially applied chelating agents. After treating with FW-CA, the exchangeable and bound to carbonate fraction of Pb decreased by 5.08% and 18.57%, respectively, contributing to a low environmental risk class of the Pb assessment code. FW-CA effectively chelated Pb at a wider range of leaching pH (3.19-11.24), and the leachability was hardly affected by curing time, which were attributed to the presence of dithiocarbamate group and formation of cross-linked structure between Pb and sulfur. Overall, the unique waste-utilized chelating agent was a suitable alternative for Pb stabilization in MSWI-FA.

Nitrogen removal performance of high ammonium and high salt wastewater by adding carbon source from food waste fermentation with different acidogenic metabolic pathways

Food waste fermentation liquid components, mainly lactate and volatile fatty acids (VFAs), can be used as alternative carbon sources to improve the nitrogen removal efficiency. To investigate the effects of carbon sources generated from food waste (FW) fermentation liquid on nitrogen removal for the treatment of high ammonium and high salt wastewater (HAHS), the lactate, acetate, propionate, butyrate, and their mixtures were added in activated sludge systems operating over 130-days. Lactate and butyrate inhibited nitrifiers by enriching polyphosphate accumulating organisms (PAOs), thus deteriorated nitrogen removal after a long-term period. When fed with acetate or propionate, the dominant glycogen accumulating organisms (GAOs) groups simultaneously realized nitrification and denitrification. The mixed carbon source enhanced microbial community robustness and the transformation of Polyhydroxyalkanoate (PHA), advancing nitrogen removal efficiency. Mixed carbon source of acetate-propionate was preferred, in which the coexisting groups of GAOs and PAOs enhanced the denitrification rate of denitrifiers and kept balancing with nitrifiers, where the highest denitrification rate (DNR) was 1.05 mg N/(h·g VSS) and the average TN removal efficiency was above 98% under the maximum nitrogen load of 0.48 kg N/(kg VSS·d). In addition, the primary pathways of nitrogen removal were heterotrophic nitrification and denitrification, since the autotrophic nitrifiers were inhibited by the free ammonium and salinity. This study illustrated the differences of nitrogen removal performance and mechanisms with fermentation liquid components as carbon sources processing of HAHS wastewater.

Nitrogen Removal from Mature Landfill Leachate via Anammox Based Processes: A Review

Mature landfill leachate is a complex and highly polluted effluent with a large amount of ammonia nitrogen, toxic components and low biodegradability. Its COD/N and BOD5/COD ratios are low, which is not suitable for traditional nitrification and denitrification processes. Anaerobic ammonia oxidation (anammox) is an innovative biological denitrification process, relying on anammox bacteria to form stable biofilms or granules. It has been extensively used in nitrogen removal of mature landfill leachate due to its high efficiency, low cost and sludge yield. This paper reviewed recent advances of anammox based processes for mature landfill leachate treatment. The state of the art anammox process for mature landfill leachate is systematically described, mainly including partial nitrification–anammox, partial nitrification–anammox coupled denitrification. At the same time, the microbiological analysis of the process operation was given. Anaerobic ammonium oxidation (anammox) has the merit of saving the carbon source and aeration energy, while its practical application is mainly limited by an unstable influent condition, operational control and seasonal temperature variation. To improve process efficiency, it is suggested to develop some novel denitrification processes coupled with anammox to reduce the inhibition of anammox bacteria by mature landfill leachate, and to find cheap new carbon sources (methane, waste fruits) to improve the biological denitrification efficiency of the anammox system.

Microbial community response of the full-scale MBR system for mixed leachates treatment

In practice, mature landfill leachate and incineration (young) leachate are mixed to improve the biodegradability and enhance biological treatment performance. However, the ratio of mature-to-young leachates greatly influences MBR treatment efficiency and microbial community structure. This study investigated the treatment efficiency and microbial community structure of full-scale MBR systems operated under two mix ratios, mature leachate: young leachate = 7:3 (v/v, denoted as LL) and 3:7 (v/v, denoted as IL). LL group showed lower Cl- and COD concentrations but a higher aromatic organic content comparing to IL group, and the COD and UV254 removals for LL were significantly lower than those for IL by MBR treatment. Microbial community structures were similar in both groups at phylum level, with dominant phyla being Proteobacteria (23.8%-32.3%), Bacteroidetes (15.25%-20.7%), Chloroflexi (10.5%-23.1%), and Patescibacteria (9.9%-13.2%). However, the richness and diversity of LL group were lower, and differences were observed at lower taxonomy levels. Results indicated that salinity mainly changed the structure of microbial community, resulting in greater abundance of salt-tolerant microbials, while refractory organics affected microbial community structure, and also led to decreased diversity and metabolic activity. Therefore, in mixed leachates biological treatment, a higher young leachate ratio is recommended for better organics removal performance. PRACTITIONER POINTS: The trade-off between refractory organics and salinity in mixed leachate treatment should be paid attention. Refractory organics reduced alpha and functional diversities of microorganisms. Mixed leachate with a higher young leachate ratio reached a better organic removal.

Sewage denitrification performance and sludge properties variation with the addition of liquid from perishable organic anaerobic fermentation

The organics in the classified wet waste were deficiently utilized while sewage denitrification requires abundant carbon sources. Herein, the fermentation of perishable organic waste (POW) and the denitrification process with obtained liquid were investigated. The most volatile fatty acids (VFAs) production was realized with the fermentation liquid of food waste (FL-FW). Increasing substrate tended to lower the proportion of VFAs and acetic acid in FL-FW. Under the optimum conditions of FL-FW carbon source, carbon to nitrogen ratio 7, and temperature 30 ℃, the removal efficiency of nitrate nitrogen reached 99.23% within 4 h. The sludge settleability and microbial activity were significantly enhanced, contributing to the actual sewage a promotional removal of organics (95.84%) and nitrogen (70.31%) with the supplementation of FL-FW. High addition ratio would cause more degradation of refractory organics, which confirmed the feasibility of using FL-FW as a cost-efficient carbon source for the denitrification.

Enhanced Denitrification of Integrated Sewage Treatment System by Supplementing Denitrifying Carbon Source

Integrated sewage treatment system (ISTY) is a new technology for rural domestic sewage treatment. In the ISTY, the carbon source in the denitrification stage is often insufficient, affecting the denitrification efficiency. In order to improve the denitrification efficiency, several commonly available agricultural wastes, peanut shell (PS), sawdust (SD), peat (PT), and their mixtures (MT), were selected as supplementary carbon sources in the denitrification stage of ISTY to study the denitrification efficiency. Results show that PS exhibited a high carbon release capacity. PS released an enormous amount of carbon in 144 h, and the cumulative total organic carbon was 41.99 ± 0.7 mg/(g·L). The optimum carbon source dosage was 3 g/L, the nitrate removal rates of PS exceeded 95% after 48 h, and the denitrification rates were 9.35 mg/(g·L), which were 63.92% higher than that of the control group. After running the ISTY for 120 h, and with PS as supplementary carbon sources, the removal rate of TN increased from 29.76% to 83.86%. At the genus level, the dominant denitrifying bacteria in ISTY, after adding PS, were Pseudomonas and Cupriavidus, accounting for 78.68%, an increase of 72.90% compared with the control group. This evidence suggested that PS can obviously enhance the denitrification efficiency of the ISTY as a supplementary carbon source.