The presence of antibiotics in animal manure represents a significant concern with respect to the introduction of antibiotic residues to the environment and the development of antibiotic-resistant pathogens. In this review, we have (1) compiled reported detections of antibiotics in poultry litter, swine manure, and cattle manure; and (2) discussed the treatment of antibiotics during conventional agricultural waste management practices. The most reported antibiotics in animal manure were fluoroquinolones, sulfonamides, and tetracyclines, all of which the World Health Organization has listed as critically important for human health. Relatively high treatment efficiencies were observed for antibiotics in composting, anaerobic digestion, and aerobic/anaerobic lagooning. Interestingly, active management of compost piles did not demonstrate a significant increase in antibiotic degradation; however, low- and high-intensity compost systems exhibited high treatment efficiencies for most antibiotics. Anaerobic digestion was not effective for some key antibiotics, including lincosamides and select sulfonamides and fluoroquinolones. Given the potential for energy recovery during anaerobic digestion of agricultural waste, efforts to optimize antibiotic degradation represent an important area for future research. Lagoons also exhibited fairly high levels of antibiotic treatment, especially for aerobic systems; however, the operational costs/complexity of these systems inhibit utilization at the full-scale. No overall trends in antibiotic treatment efficiency during these three agricultural waste management practices were observed. Finally, we posit that increased efforts to include analysis of antibiotic residues in animal manure in national surveillance programs will provide important information to address concerns over the continued use of antimicrobials in animal feeding operations.

Worldwide, crude palm oil industries generate an overwhelming amount of palm oil mill effluent (POME). Since the past few decades, environmental issues associated with POME disposal have challenged the palm oil-producing nations which led them to reevaluate and develop their waste management strategies by using advanced biotreatment technologies. With the help of these technological advances, POME has emerged as a valuable biomass resource with great potential to produce sustainable renewable resources like biogas. This review entails various POME treatment methods in vogue and offers an insight into their improved applicability potential and pollution mitigation strategies by using proposed improved configurations like ponding system, open digesting tanks, anaerobic digestion based-bioreactors, aerobic anaerobic hybrid bioreactors, and membrane bioreactors. This review paper also gives an overview about the recent advancements in POME treatment bioreactor configurations and emphasizing their scope in large-scale applications on an industrial level. This review also critically analyzes their performance level to achieve the standard POME discharge limit by efficiently removing high COD (chemical oxygen demand), BOD (biological oxygen demand), and TSS (total suspended solid).

PURPOSE OF REVIEW: Organic solid wastes (OSWs) have great potential for resourceful applications. However, individual treatment technologies are difficult to effectively recover their resources. This review aims to describe the development of solid-state anaerobic digestion (SS-AD), digestate aerobic composting, and their hybrid technology (SSADAC) for OSWs treatment to maximize resource recovery from OSWs. RECENT FINDINGS: SSADAC exhibits high potential for OSW treatment in energy and nutrient recovery. As individual treatment technologies, SS-AD and digestate composting recover energy and nutrients in terms of methane and compost, respectively. However, some deficiencies of these individual treatment technologies are hard to be ignored, such as energy loss and liquid digestate/leaching discharge. SSADAC can alleviate these issues with fully synergizing the characteristics of two treatment units for multi-target products. Thus, recent studies have proposed that the regulation of digestion duration can improve SSADAC performance, and other potential methods can also improve the value of SSADAC, such as raw material regulation and exogenous additives, to achieve zero waste discharge and maximum resource recovery. This review presents the applications of SS-AD and digestate composting for OSW treatment and illustrates the development and potential improvements of SSADAC as an integrated process. Key issues and their potential counter-measurements were displayed to provide the further development of SSADAC.

PURPOSE OF REVIEW: Membrane techniques have been employed to concentrate livestock manure effluent from anaerobic digestion to produce highly concentrated liquid organic fertilizer. This review aims to provide a comprehensive understanding on the opportunities and challenges of membrane processes in the concentration of digested effluent for their further implementation. RECENT FINDINGS: Anaerobic digestion has been deployed to convert livestock manure into biogas (energy) and digestate with high potential as biofertilizer. Digestate can be separated into a solid and liquid fraction to reduce required capacity for onsite storage. The liquid fraction, known as digested effluent, remains a vexing challenge to digestate management due to the contradiction between its continuous production and seasonal application to farmlands, particularly in developing countries. Recent investigation has demonstrated the promise of membrane techniques for the concentration of digested effluent to recover recycling water and produce nutrient-rich liquid fertilizer. These techniques mainly include hydraulically driven membrane processes (from microfiltration to reverse osmosis), forward osmosis, membrane distillation, and electrodialysis. In most cases, these membrane techniques are hybridized to enhance the concentration efficiency. Nevertheless, the practical application of these membrane processes is hindered by several technical challenges, which mainly include membrane fouling, contaminant enrichment, ammonia volatilization, and high economic input. In this paper, we critically reviewed the performance of different membrane processes in the concentration of digested livestock manure effluent. Key technical challenges and their potential countermeasures were elucidated. Furthermore, future perspectives were provided to shed light on further development of membrane concentration techniques in the field.

Food waste constitutes the largest component of municipal solid waste in many urbanized societies. The current practice of disposing of biodegradable food waste mixed with other solid wastes to landfills is not sustainable and is environmentally undesirable. Moreover, the leakage of nutrient-rich food waste leachate (FWL) impacts the environment by eutrophication of the water body. Two robust microalgal species, Dunaliella tertiolecta (D. tertiolecta) and Cyanobacterium aponinum (C. aponinum), have been selected previously for the treatment of FWL because they can tolerate diluted FWL. However, growth suppression by some inhibiting factors, such as total suspended solids and organic nitrogen, limited biomass productivity, and substantial dilution (5–10% v/v FWL) was required. To alleviate this suppression, anaerobic bacterial digestion was proposed to pretreat FWL and convert certain nutrients such as organic nitrogen to ammonium. The pretreatment was optimized in neutral to slightly alkaline media, where a byproduct of biomethane up to 4.67 L methane/kg COD was produced. In addition, digestate after anaerobic ammonification can provide sufficient inorganic nutrients for subsequent microalgal biofuel production. Through batch cultivation, 50% (v/v) of anaerobic bacterial pretreated FWL digestate can be fed to D. tertiolecta, with biomass productivity of up to 0.88 g/L/day, and biomass productivity can be increased to 0.34 g/L/day for C. aponinum at 30% FWL digestate. Regarding the nutrient removal efficiency, 98.99% of total nitrogen and 65% of total phosphorus can be removed by D. tertiolecta, whereas more than 80% of total nitrogen and 65% of total phosphorus can be removed by C. aponinum. The use of anaerobic bacterial ammonification pretreatment can significantly improve the performance of subsequent microalgal treatments and has been shown to be a sustainable green technology for biofuel production and FWL recycling.

This study used biogas residue produced by anaerobic fermentation of food waste as the raw material in large-scale windrow composting. The effects of the addition of a microbial consortium on the physical and chemical properties and stability of composting of biogas residue were studied. The maturity of food waste biogas residue during composting was investigated by multivariate interaction of environmental, maturity, and nutrient parameters, using structural equation modeling (SEM). Results showed that the temperature of T2 compost with the microbial consortium increased more rapidly. The pH ranges of T1 (without the microbial consortium) and T2 were 8.75–9.15 and 8.42–9.27, respectively; the electrical conductivity (EC) ranges of T1 and T2 were 2.74–3.95 mS/cm and 2.81–3.85 mS/cm, respectively; the degradation rates of organic matter (OM) in T1 and T2 were 21.74% and 33.62%, respectively; and the total nitrogen (TN) ranges of T1 and T2 were 1.93–3.10% and 1.80–3.21%, respectively. By the end of composting, the germination indices (GI) of T1 and T2 were 20.57% and 64.24%, respectively. The total oxygen consumption after 4 days (AT₄) was 1.88 mg-O₂/g and 1.2 mg-O₂/g in T1 and T2, respectively. SEM of T1 showed that compost temperature and EC were important factors affecting compost maturity. These factors highly significantly affected OM, which in turn affected AT₄ of the biogas residue composting. SEM of T2 showed that compost temperature, pH, and EC affected OM, which in turn affected compost maturity. Temperature affected compost maturity by affecting AT₄ and GI. Principal component analysis (PCA) showed that the overall score of T2 was higher than that of T1, indicating that the addition of the microbial consortium was beneficial for industrial-scale composting of biogas residue produced by anaerobic digestion of food waste.

Anaerobic digestion of thermally hydrolyzed sludge was an important method for sludge treatment. But a large amount of rejected water (TRW) containing high ammonia was produced, which was difficult to treat. In this study, two-stage reactors were used for TRW treatment using partial nitrification-anammox technology. The results demonstrated that nitritation initiated rapidly. The NH₄⁺–N conversion load reached 1300 mg N/(L·day) and could be further improved. The consumption of NH₄⁺–N and the formation of NO₂⁻–N were linear with time. So, the right ratio of NH₄⁺–N/NO₂⁻–N can achieve by controlling time for anammox. Dissolved oxygen and sludge concentration had important effects on nitritation. Increasing dissolved oxygen or sludge concentration can shorten the reaction time. Nitrosomonas were the dominant ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria were not detected. Aerobic treatment achieved more than 50% chemical oxygen demand removal in TRW, and this water was used in an anammox reactor. Accumulated flocculent sludge could inhibit anammox activity but could be removed by increasing the flow velocity. The anammox reactor load was above 600 mg N/(L·day); even under high conductivity (18.2 ms/cm) condition, the load reached 320 mg N/(L·day), and the total nitrogen removal rate was greater than 85% under stable condition. After approximately 190 days of operation, the abundance of anammox bacteria decreased from 29% to less than 10%, but the reactor operated stably. The results demonstrated two-stage reactors were suitable for ammonia removal in TRW using partial nitrification-anammox technology.

Swine manure treatment plants are important reservoirs of plasmid-harboring antibiotic resistance genes (ARGs) and physicochemical contaminants, but the changes in the abundances of plasmids and ARGs, and their interactions with the physicochemical properties of manure, are still unclear. Thus, in the present study, plasmidome and metagenome analyses were conducted for samples collected at different stages in the swine manure treatment process. The results indicated that anaerobic digestion and aerobic digestion were the most efficient stages for reducing the abundances of ARGs in swine manure. However, the plasmids associated with ARGs were not effectively removed in these stages. Through the whole treatment process, the IncL/M, IncQ1, IncHI2A, IncA/C, and IncN plasmid groups had strong correlations (r > 0.8, P < 0.01) with most ARG types, thereby indicating that these plasmids play important roles in the persistence of ARGs in this environment. Furthermore, the pH, total nitrogen, total phosphorus, and four heavy metals (Cu, Zn, As, and Fe) significantly affected the abundances of seven ARG subtypes (tetB(P), ant(6)-Ia, tet44, aph(3′′)-Ib, mefB, tet(L), and tet(39)). In particular, florfenicol had the most positive correlations with ARGs. Our results indicated that nutrients, heavy metals, and antibiotics all contributed to the presence and persistence of plasmid-harboring ARGs. This study provides insights into the fate of plasmids and ARGs, and related factors during the swine manure treatment process, thereby facilitating the development of a new treatment technique for removing ARGs and reducing the public health risk associated with livestock production.

Alkaline pretreatment (APT) is the promising disintegration pretreatment for the anaerobic digestion (AD) of sewage sludge (SS) to improve digestion efficiency and methane yields. In this study, the heavy metals (HMs) were observed to be leached from SS in the APT process, which could lower the HMs secondary pollution risk of the residual biosolids after AD in land application. The sequential chemical extraction (SCE) experiment was performed to determine the variation in HMs’ distribution prior to and after the APT. The alkaline extracts were characterized in order to elucidate the HMs’ release mechanism. The APT could cause significant release of Zn and Cu with a maximum release efficiency of 96.6% ± 4.6% and 62.7% ± 8.4% under the condition of 1.5 mol/L NaOH and 25 ℃, respectively. The release efficiency of Zn and Cu was reduced by 63.0% and 21.7%, respectively, due to the extra addition of 0.25 mol/L NaCl at a NaOH concentration of 1.25 mol/L in the APT process. The release of Zn and Cu may be attributed to a complex process including disruption of microbial cells in SS, solubilization of organic matters bounded with metals, and the chemical leaching reaction of minerals. This study demonstrates the possibility to remove the Zn and Cu from the SS in the APT process before the AD disposal.

The objective of this research was to evaluate anaerobic co-digestion of guinea pig manure (GP) with Andean agricultural residues such as amaranth (AM), quinoa (QU) and wheat (TR) in batch biodigesters under mesophilic conditions (37 ⁰C) for 40 days. As microbial inoculum, sewage treatment sludge was used in two inoculum/substrate ratios (ISR of 1 and 2). In terms of methane production, the best results occurred in treatments containing AM and QU as co-substrate and an ISR of 2. Thus, the highest methane production yield in the GP:AM biodigesters (25:75) and GP:QU (25:75) with 341.86 mlCH₄/g VS added and 341.05 mlCH₄/g VS added, respectively. On the other hand, the results showed that methane production with an ISR of 2 generated higher yields for guinea pig waste and the methane fraction of the biogas generated was in a range from 57 to 69%. Methane production kinetics from these raw materials was studied using five kinetic models: modified Gompertz, logistic equation, transfer, cone and Richards. The cone model adjusted best to the experimental values ​​with those observed with r² of 0.999 and RMSE of 1.16 mlCH₄/g VS added. Finally, the highest biodegradability (experimental yield/theoretical yield) was obtained in the GP-AM biodigesters (25:75) with 67.92%.