Biofilm-based simultaneous nitrification, denitrification, and phosphorous uptake in wastewater by Neurospora discreta

Biological removal of nitrogen and phosphorous from wastewater conventionally involves multiple processing steps to satisfy the differing oxygen requirements of the microbial species involved. In this work, simultaneous nitrification, denitrification, and phosphorous removal from synthetic wastewater were achieved by the fungus Neurospora discreta in a single-step, biofilm-based, aerobic process. The concentrations of carbon, nitrogen, and phosphorous in the synthetic wastewater were systematically varied to investigate their effects on nutrient removal rates and biofilm properties. Biofilm growth was significantly (p < 0.05) affected by carbon and nitrogen, but not by phosphorous concentration. Scanning electron microscopy revealed the effects of nutrients on biofilm microstructure, which in turn correlated with nutrient removal efficiencies. The carbohydrate and protein content in the biofilm matrix decreased with increasing carbon and nitrogen concentrations but increased with increasing phosphorous concentration in the wastewater. High removal efficiencies of carbon (96%), ammonium (86%), nitrate (100%), and phosphorus (82%) were achieved under varying nutrient conditions. Interestingly, decreasing the phosphorus concentration increased the nitrification and denitrification rates, and decreasing the nitrogen concentration increased the phosphorus removal rates significantly (p < 0.05). Correlations between biofilm properties and nutrient removal rates were also evaluated in this study

Investigation of the effect of equal and unequal feeding time intervals on process stability and methane yield during anaerobic digestion grass silage

The effects of equal and unequal feeding intervals, organic loading rates (OLR) and operating temperatures on specific methane production (SMP) during the anaerobic digestion (AD) process were investigated using three pairs of continuously stirred tank reactors (CSTRs). The Pair 1, 2 and 3 CSTRs were operated at psychrophilic (25 ± 2 °C), mesophilic (40 ± 3 °C) and thermophilic (60 ± 2.5 °C) conditions, respectively. After acclimatization, the reactors were fed at an OLR of 1.0 and 1.5gVS/L.d at selected intervals, while maintaining their pH 6.8–7.2 with NH4HCO3 solution. The results showed that during uneven feeding regime (day 8–93), the mean SMP from Pair 1, 2 and 3 reactors were 294.5, 433.5 and 370.2 N mLCH4/gVS fed, respectively. At failing state (day 60–93), the mean concentrations of free ammonia nitrogen (FAN) in the psychrophilic, mesophilic and thermophilic CSTRs were 19.1, 33.7 and 127.2 mg/L; VFAs of 6940.1, 6852.3 and 4694.9 mg HAc/L; which reduced their SMPs to 140, 273.8 and 231.1 N mLCH4/gVS, respectively. Therefore, uneven feeding, trace elements (TEs) deficiency, VFAs accumulation and FAN (for thermophilic) led to CSTRs failure. An even (24-hourly) feeding regime with daily biomass ash-extracts supplement enhanced the recovery of the failed CSTRs. Although, uneven daily feeding conditions led to AD process instability, it favoured SMP in mesophilic CSTRs compared to psychrophilic and thermophilic. These results strongly indicate that the soluble TEs and alkalinity contained in ash-extracts facilitated the recovery of the failed AD reactors and therefore can be used to revive failed AD processes