Influence of Anaerobic Mesophilic and Thermophilic Digestion on Cytotoxicity of Swine Wastewaters

Plasticizers inhibit food waste anaerobic digestion performance by affecting microbial succession and metabolism

The widely existed plastic additives plasticizers in organic wastes possibly pose negative influences on anaerobic digestion (AD) performance, the direct evidence about the effects of plasticizers on AD performance is still lacking. This study evaluated the influencing mechanism of two typical plasticizers bisphenol A (BPA) and dioctyl phthalate on the whole AD process. Results indicated that plasticizers addition inhibited methane production, and the inhibiting effects were reinforced with the increase of concentration. By contrast, 50 mg/L BPA exhibited the strongest inhibition on methane production. Physicochemical analysis showed plasticizers inhibited the metabolism efficiency of soluble polysaccharide and volatile fatty acids. Microbial communities analyses suggested that plasticizers inhibited the direct interspecies electron transfer participators of methanogenic archaea (especially Methanosarcina) and syntrophic bacteria. Furthermore, plasticizers inhibited the methane metabolisms, key coenzymes (CoB, CoM, CoF420 and methanofuran) biosynthesis and the metabolisms of major organic matters. This study shed light on the effects of plasticizers on AD performance and provided new insights for assessing the influences of plasticizers or plastic additives on the disposal of organic wastes.

Non-immersed zigzag microalgae biofilm overcoming high turbidity and ammonia of wastewater for muti-pollutants bio-purification

Biological treatment that utilizes microalgae technology has demonstrated outstanding efficacy in the wastewater purification and nutrients recovery. However, the high turbidity of the digested piggery wastewater (DPW) leads to serious light attenuation and the culture mode of suspended microalgae results in a huge landing area. Thus, to overcome light attenuation in DPW, a non-immersed titled zigzag microalgae biofilm was constructed by attaching it onto a porous cotton cloth. As a result, the light could directly irradiate microalgae biofilm that attached on both sides of the cotton cloth, and the microalgal biofilm area was up to 6 m2 per bioreactor landing area. When the non-immersed zigzag microalgae biofilm bioreactor (N-Z-MBP) was used to treat wastewater with an ammonia nitrogen (NH4+-N) concentration of 362 mg L-1, the NH4+-N was completely removed in just 5 days and the maximum growth rate of microalgae biofilm reached 7.02 g m-2 d-1. After 21 days of long-term sequencing batch operation for the N-Z-MBP, the biomass density of the biofilm reached 52 g m-2 and remained at this high value for the next 14 days. Most importantly, during the 35 days' running, the NH4+ -N maximum removal rate of single batch reached up to 65 mg L-1 d-1 and its concentration in the effluent was always below the discharge standard value (80 mg L-1 form GB18596-2001 of China) and total phosphorus was completely removed in each batch. Furthermore, the biomass concentration of microalgae cells in the effluent of the N-Z-MBP was almost zero, indicating that the non-submerged biofilm achieved in situ separation of microalgae from the wastewater. This work suggests that the N-Z-MBP can effectively purify DPW over a long period, providing a possible strategy to treat wastewater with high ammonia nitrogen and high turbidity.

Effects of ammonia on electrochemical active biofilm in microbial electrolysis cells for synthetic swine wastewater treatment

When facing wastewater with high organic and ammonia, e. g. swine wastewater, microbial electrolysis cell (MEC) is emerging for energy extraction as hydrogen and methane. However, the effects of highly concentrated ammonia on MEC haven't been fully evaluated. In this study, single-chamber MECs were operated with acetate and sucrose as substrates under various ammonia concentrations. The current generally increased with ammonia loading from 80 to 3000 mg L^-1. Yet, the substrate consumption in MECs was inhibited with ammonia concentrations above 1000 mg L^-1. As a combined result, the energy recovery efficiency of MECs was stable. The electrochemical activity of anode biofilm reached the peak under 1000 mg L^-1 ammonia and was restricted under higher ammonia loadings. Under neutral pH, the NH₄⁺ increases the cell membrane permeability, which benefited the electrochemical activity of exoelectrogens to a proper extent. Nevertheless, the toxic ammonia also accelerated the anode biomass loss and stimulated the extracellular polymeric substance (EPS) secretion. Due to the current increase, the abundance of exoelectrogens generally raised with ammonia loading from 80 to 3000 mg L^-1. However, except for anode biomass loss, the carbon and methane metabolism pathways were inhibited in acetate-fed MEC, while the glycolysis acted as the rate-limiting step for substrate degradation in sucrose-fed conditions. This study systematically examined the influences of high ammonia loading on MEC performances, bio-community and anode electrochemical activities, and evaluated practical feasibility and application inch of MECs for the energy recovery and pollutant removal of high concentration organic and ammonia wastewater.

Application of response surface methodology for COD and ammonia removal from municipal wastewater treatment plant using acclimatized mixed culture

This study aimed to optimize conditions influencing the removal of chemical oxygen demand (COD) and ammonia-N in municipal wastewater by using acclimatized mixed culture (AMC). Two-level factorial analysis was used to investigate the factors affecting the degradation of COD and ammonia-N (%); ratio of synthetic wastewater (SW) to acclimatized mixed culture (AMC) (1:1 and 3:1), presence and absence of support media (Yes and No), agitation (0 rpm and 100 rpm) and hydraulic retention time (HRT) (2 and 5 days). A central composite design (CCD) under response surface methodology (RSM) determined the optimum agitation (0 rpm and 100 rpm) and retention time (2 and 5 days). The best conditions were at 3:1 of SW: AMC ratio, 100 rpm agitation, without support media, and 5 days retention time. COD and ammonia-N removal achieved until 57.23% and 43.20%, respectively. Optimization study showed the optimum conditions for COD and ammonia-N removal were obtained at 150 rpm agitation speed and 5 days of retention time, at 70.41% and 64.29% respectively. This study discovers the conditions that affect the COD and ammonia-N removal in the municipal wastewater using acclimatized mixed culture.

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Removal of COD and ammonia-N using acclimatized mixed culture.

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Central composite design was used to optimize process condition.

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The maximum COD removal was found to be 70.41%.

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The maximum ammonia-N removal was found to be 64.29%.

Metatranscriptomic insight into the effects of antibiotic exposure on performance during anaerobic co-digestion of food waste and sludge

Antibiotics are inevitably entered into anaerobic co-digestion (AcoD) system of food waste (FW) and sludge along with the addition of abundant antibiotic-containing activated sludge. However, the in-depth insights into antibiotics affecting AcoD performance have not comprehensively studied. In present study, the results showed that tetracycline (TC), sulfamethoxazole (SMZ) and erythromycin (ERY) inhibited and delayed methane production except for 5 mg/L ERY. By comparison, TC and SMZ significantly inhibited the cumulative methane yields (one-way ANOVA, p < 0.01), and the inhibition effects were magnified as the antibiotic level increased. Physicochemical and methane yield analysis indicated antibiotics inhibited hydrolysis process and delayed methanogenesis process, which was in line with the declined abundance of acetogenic Proteiniphilum and hydrogenotrophic Methanobacterium during AcoD. Furthermore, metatranscriptomic analysis demonstrated the microbial activities of major organic and energy metabolism were down-regulated under antibiotics exposure, thereby down-regulating the expressions of key coenzymes (coenzymes M, F420, methanofuran) biosynthesis for methanogenesis and methane metabolism. The declined methanogenesis activity was completely consistent with the inhibited activity of dominant Methanosarcina and methane production, proving the importance of Methanosarcina on methane production. This study provides new metatranscriptomic evidence into the effects of antibiotics on methanogenesis during AcoD.

Comparison of Estrogenic, Spectroscopic, and Toxicological Analyses of Pilot-Scale Water, Wastewaters, and Processed Wastewaters at Select Military Installations

Reuse of water requires the removal of contaminants to ensure human health. We report the relative estrogenic activity (REA) of reuse treatment design scenarios for water, wastewaters, and processed wastewaters before and after pilot-scale treatment systems tested at select military facilities. The comparative relationships between REA, several composite toxicological endpoints, and spectroscopic indicators were evaluated for different reuse treatment trains. Four treatment processes including conventional and advanced treatments reduced the estrogenicity by at least 33%. Biologically based methods reduced estrogenicity to below detection levels. Conventional treatment scenarios led to significantly less reduction of adverse biological endpoints compared to the advanced treatment scenarios. Incorporating the anaerobic membrane bioreactor reduced more endpoints with higher reduction percentages compared to the sequencing batch reactor design. Membrane technology and advanced oxidation generated reductions across all biological endpoints, from 65% (genotoxicity) to 100% (estrogenicity). The design scenarios featuring a low-cutoff mechanical screen filter, intermittent activated carbon biofilter, and membrane filtration achieved the highest percent reduction and produced water with the lowest negative biological endpoints. Spectroscopic indicators demonstrated case-specific relationships with estrogenicity and toxicity. Estrogenicity consistently correlated with cytotoxicity and thiol reactivity, indicating the potential for preliminary estrogenicity screening using thiol reactivity.

Quantification and Comparison of Risks Associated with Wastewater Use in Spray Irrigation

In the U.S., spray irrigation is the most common method used in agriculture and supplementing with animal wastewater has the potential to reduce water demands. However, this could expose individuals to respiratory pathogens such as Legionella pneumophila and nontuberculosis Mycobacteria (NTM). Disinfection with methods like anaerobic digestion is an option but can increase concentrations of cytotoxic ammonia (personal communication). Our study aimed to model the annual risks of infection from these bacterial pathogens and the air concentrations of ammonia and determine if anaerobically digesting this wastewater is a safe option. Air dispersion modeling, conducted in AERMOD, generated air concentrations of water during the irrigation season (May-September) for the years 2013-2018. These values fed into the quantitative microbial risk assessments for the bacteria and allowed calculation of ammonia air concentrations. The outputs of these models were compared to the safety thresholds of 10^-4 infections/year and 0.5 mg/m³ , respectively, to determine their potential for negative health outcomes. It was determined that infection from NTM was not a concern for individuals near active spray irrigators, but that infection with L. pneumophila could be a concern, with a maximum predicted annual risk of infection of 3.5 × 10^-3 infections/year and 25.2% of parameter combinations exceeding the established threshold. Ammonia posed a minor risk, with 1.5% of parameter combinations surpassing the risk threshold of 0.5 mg/m³ . These findings suggest that animal wastewater should be anaerobically digested prior to use in irrigation to remove harmful pathogens.

Toxicity of hydraulic fracturing wastewater from black shale natural-gas wells influenced by well maturity and chemical additives

Hydraulic fracturing of deep shale formations generates large volumes of wastewater that must be managed through treatment, reuse, or disposal. Produced wastewater liberates formation-derived radionuclides and contains previously uncharacterized organohalides thought to be generated within the shale well, both posing unknown toxicity to human and ecological health. Here, we assess the toxicity of 42 input media and produced fluid samples collected from four wells in the Utica formation and Marcellus Shale using two distinct endpoint screening assays. Broad spectrum acute toxicity was assessed using a bioluminescence inhibition assay employing the halotolerant bacterium Aliivibrio fischeri, while predictive mammalian cytotoxicity was evaluated using a N-acetylcysteine (NAC) thiol reactivity assay. The acute toxicity and thiol reactivity of early-stage flowback was higher than later produced fluids, with levels diminishing through time as the natural gas wells matured. Acute toxicity of early stage flowback and drilling muds were on par with the positive control, 3,5-dichlorophenol (6.8 mg L-1). Differences in both acute toxicity and thiol reactivity between paired natural gas well samples were associated with specific chemical additives. Samples from wells containing a larger diversity and concentration of organic additives resulted in higher acute toxicity, while samples from a well applying a higher composition of ammonium persulfate, a strong oxidizer, showed greater thiol reactivity, predictive of higher mammalian toxicity. Both acute toxicity and thiol reactivity are consistently detected in produced waters, in some cases present up to nine months after hydraulic fracturing. These results support that specific chemical additives, the reactions generated by the additives, or the constituents liberated from the formation by the additives contribute to the toxicity of hydraulic fracturing produced waters and reinforces the need for careful consideration of early produced fluid management.

Advances towards understanding long chain fatty acids-induced inhibition and overcoming strategies for efficient anaerobic digestion process

The inhibition of the anaerobic digestion (AD) process, caused by long chain fatty acids (LCFAs), has been considered as an important issue in the wastewater treatment sector. Proper understanding of mechanisms behind the inhibition is a must for further improvements of the AD process in the presence of LCFAs. Through analyzing recent literature, this review extensively describes the mechanism of LCFAs degradation, during AD. Further, a particular focus was directed to the key parameters which could affect such process. Besides, this review highlights the recent research efforts in mitigating LCFAs-caused inhibition, through the addition of commonly used additives such as cations and natural adsorbents. Specifically, additives such as bentonite, cation-based adsorbents, as well as zeolite and other natural adsorbents for alleviating the LCFAs-induced inhibition are discussed in detail. Further, panoramic evaluations for characteristics, various mechanisms of reaction, merits, limits, recommended doses, and preferred conditions for each of the different additives are provided. Moreover, the potential for increasing the methane production via pretreatment using those additives are discussed. Finally, we provide future horizons for the alternative materials that can be utilized, more efficiently, for both mitigating LCFAs-based inhibition and boosting methane potential in the subsequent digestion of LCFA-related wastes.