Microbial Community Structure of a Leachfield Soil: Response to Intermittent Aeration and Tetracycline Addition

Mesocosm- and Field-Scale Evaluation of Lignocellulose- Amended Soil Treatment Areas for Removal of Nitrogen from Wastewater

Non-proprietary N-removal onsite wastewater treatment systems are less costly than proprietary systems, increasing the likelihood of adoption to lower N inputs to receiving waters. We assessed the capacity of non-proprietary lignocellulose-amended soil treatment areas (LCSTAs)—a 45-cm-deep layer of sand above a 45-cm-deep layer of sand and sawdust—to lower the concentration of total N (TN) in septic tank effluent (STE) at mesocosm and field scales. The mesocosm received wastewater for two years and had a median effluent TN concentration of 3.1 mg/L and TN removal of 60–100%, meeting regulatory standards of 19 mg/L or 50% removal. Removal varied inversely with temperature, and was lower below 10 °C. Removal was higher in the mesocosm than in five field sites monitored for 12–42 months. Median effluent TN concentration and removal met the standard in three continuously-occupied homes but not for two seasonally-occupied homes. Sites differed in temporal pattern of TN removal, and in four of five sites TN removal was greater—and effluent TN concentration lower—in the LCSTA than in a control STA containing only sand. The performance of non-proprietary LCSTAs was comparable to that for proprietary systems, suggesting that these may be a viable, more affordable alternative for lowering N inputs to receiving waters.

Simultaneous oxidation of ammonium and tetracycline in a membrane aerated biofilm reactor

The membrane aerated biofilms reactor (MABR) is an emerging technology in wastewater treatment with particular advantages including high rate nitrification, and very high oxygen transfer efficiencies. In this study a synthetic feed water incorporating tetracycline (TC) was investigated in a MABR. Simultaneous removal of ammonium and tetracycline (TC) in the reactor, formation of TC transformation products (TPs), and microbial community analysis in the biofilm growing on the membrane were performed. A range of TC and ammonium loading rates and the effect of different intra-membrane oxygen pressures were on treatment performance were systematically investigated. Successful nitrification and TC degradation were achieved with the highest TC removal (63%) obtained at a HRT of 18 h HRT and 0.41 bar gas pressure. It has shown that different operating conditions (HRT and gas pressure) do not cause a significant change in ammonium removal. The concentration of TPs such as ETC, EATC, and ATC was determined to be at the ppb level. Molecular results showed that MABR reactor was mainly dominated by β-proteobacteria. The relative abundance of this group decreased in parallel with the increasing ammonium and TC loading.

Exploring the Abundance and Diversity of Bacterial Communities and Quantifying Antibiotic-Related Genes Along an Elevational Gradient in Taibai Mountain, China

Thus far, no studies have investigated the soil microbial diversity over an elevational gradient in Taibai Mountain, the central massif of the Qinling Mountain Range. Here, we used Illumina sequencing and quantitative PCR of the 16S rRNA gene to assess the diversity and abundance of bacterial communities along an elevational gradient in representative vegetation soils in Taibai Mountain. We identified the soil, climate, and vegetation factors driving the variations in soil bacterial community structure by Pearson correlation and redundancy analysis. We also evaluated the potential for antibiotic discovery by quantitative PCR of the PKS-I, PKS-II, and NRPS genes from Actinobacteria. The results showed that soil bacterial alpha diversity increased first and then decreased with an elevational rise in both the northern and southern slopes of Taibai Mountain. The bacterial abundance was significantly correlated with soil organic matter and nitrate nitrogen. The average relative abundance of Actinobacteria in Taibai Mountain was markedly higher than those in other mountain forest soils. The absolute abundance of PKS and NPRS gene was significantly higher in the tested soils compared with the gene copy numbers reported in tropical urban soils. Taibai Mountain is rich in actinomycete resources and has great potential for antibiotic excavation.