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Volatile organic compounds (VOCs) become concerned pollutants in landfill gases, and their composition and concentration varied significantly during waste decomposition. Many environmental factors are known to affect VOC emissions, while the effect of indigenous bacteria in wastes on VOC production remains elusive. In this study, a simplified anaerobic degradation experiment, with the single substrate and the purified bacteria from a landfill, was set up to measure the degradation process and the dynamic changes of VOCs. The experiment excluded the abiotic factors for VOC variation. The two isolated bacteria, identified as Sporanaerobacter acetigenes and Clostridium sporogenes, could anaerobically ferment amino acids by Stickland reaction. They produced 51 and 57 species of VOCs in the experiment, respectively. The concentration changes of VOCs over bacterial growth and fermentation were clustered into four types by principal component analysis: three profiles were regular, similar to the variation of nitrate, hydrogen sulfide, and the major fermentation products (carbon dioxide, ammonium, and volatile organic acids), respectively; while one profile was unique to any degradation indicator. The various concentration profiles indicated different origins for VOCs, possibly from the extracellular environment, fermentation, and secondary reactions. The findings provide insights into the understanding of VOC diversity and variability during waste decomposition.

Solid–liquid separation makes further treatment and disposal of dairy manure easier. High concentrations of solids and long times-to-filter of anaerobically digested dairy manure present a challenge to cost-effective solid–liquid separation. This study operated a two-stage filtration system by batch modes to develop passive solid–liquid separation of anaerobically digested dairy manure. In the 1st-stage, pebble filters attained solid–liquid separation through surface filtration and evaporation. Filtration was completed after 7–33 d into each cycle of batch operation. Evaporation became the predominant mechanism for manure dewatering 2–3 weeks after each batch loading. Filtration was faster at higher temperatures, higher initial solids concentrations, and shorter times-to-filter. Two weeks after batch loadings, the pebble filters had removed 81.4–97.7% of total solids and 87.1–98.8% of total volatile solids from the filtrate and the manure retained on the pebble beds was thickened to 6.3–24.6% solids. Dewatering on the pebble beds was faster at a lower loading rate and more efficient at a higher loading rate (0.20 versus 0.16 and 0.12 m3 m−2). In the 2nd-stage, the sand filters removed suspended solids via depth filtration.

Ultrasonic irradiation as a pretreatment of Fenton-acclimation treatment was investigated to enhance the efficiency of sludge reduction and effectiveness of operating cost. A series of batch experiments were conducted to optimize the reaction conditions for ultrasonic–Fenton treatment. Separate ultrasonic treatment suggested that input power of 0.4 W/mL and ultrasonic time of 10 min were the optimal conditions for sludge disintegration, and the efficiency was reduced with the increase of sludge mixed liquor suspended solids. Separate Fenton treatment revealed that 9 g/L and 40 mg/L were the optimal dosages of H2O2 and Fe2+ respectively for sludge lysis under pH of 3. Particle distribution (75.49% of the particles distributed between 7.18 and 31.11 μm after Fenton treatment while 93.35% of the particles distributed between 4.62 and 18.50 μm after ultrasonic–Fenton treatment) and chemical oxygen demand (51.89% higher in ultrasonic–Fenton treatment than that in Fenton treatment) demonstrated that combined ultrasonic–Fenton treatment was effective in sludge disintegration compared to separate Fenton treatment. With ultrasound as pretreatment, sludge reduction rate increased from 26.53 to 63.59% with operating cost reduction of 51.46%, indicating ultrasonic irradiation was effective in improving both sludge reduction efficiency and operating cost-effectiveness.

High concentrations of ammonium and phosphate present a challenge to cost-effective treatment of anaerobically digested dairy manure. This study investigated the efficacy of a two-stage biofiltration system for passive treatment of digested dairy manure. The first stage pebble filters were batch loaded. When the slurry-like digested dairy manure was retained on pebble beds, soluble contaminants were removed before liquid infiltrated over 8–17 days. The pebble filters removed 70% of soluble chemical oxygen demand, 71% of soluble biochemical oxygen demand, 75% of ammonium, and 68% of orthophosphate. Nitrogen removal was attributed to the conventional nitrification – denitrification process and novel nitritation – anammox process. Aerobic ammonium oxidizing and anammox bacteria accounted for 25 and 23% of all bacteria, respectively, in the filtrate of the pebble filters. The longer it took for filtration, the greater the removal efficiency of soluble contaminants. The second stage sand filters had removal efficiencies of 17% for soluble chemical oxygen demand, 45% for soluble biochemical oxygen demand, 43% for ammonium, and 16% for orthophosphate during batch operations at a hydraulic retention time of 7 days. Aerobic ammonium oxidation and anammox were primarily responsible for nitrogen removal in the sand filters. Vegetation made an insignificant difference in treatment performance of the sand filters.

This study investigated the effects of paper mill effluent, waste sludge, and wheat straw residue on remediation of heavily degraded coastal saline wetlands in the Yellow River Delta, China. Five treatments were employed, i.e., plowing (P); plowing plus paper mill effluent (PE); plowing plus paper mill effluent and sludge (PES); plowing plus paper mill effluent and wheat straw residue (PER); and plowing plus paper mill effluent, sludge and wheat straw residue (PESR). Effects of the five treatments on wetland remediation were evaluated in soil properties, including bulk density, total soluble salt, organic matter, alkali-hydrolyzable N, available P and available K, microbial biomass carbon, soil respiration, and enzyme activity. All the treatments improved soil properties. The most effective treatment was PERS which significantly improved all of the soil properties, compared to the controls. In general, the effects of different treatments were in the following order: PERS>;PER>;PES>;PE>;P. Besides soil nutrients, total soluble salt was another main factor that influenced soil microbial activities.

Solid-liquid separation makes further treatment, reuse and disposal of anaerobically digested dairy manure easier. However, high concentrations of solids and and nutrients as well as long time-to-filter of anaerobically digested dairy manure present a challenge to cost-effective solid-liquid separation and treatment. This study operated a two-stage biofiltration system by batch mode for passive solid-liquid separation and treatment of anaerobically digested dairy manure. The 1st-stage pebble biofilters attained separation through filtration and evaporation. Filtration was completed in 7-32 d. Separation effectiveness was related with temperature, initial total solids concentration, and time-to-filter of digested dairy manure. The pebble biofilters removed solids, chemical oxygen demand, ammonia, and orthophosphate mainly through surface filtration and microbial decomposition. The pebble biofilters removed 88% of total solids, 63% of soluble chemical oxygen demand, 70% of soluble biochemical oxygen demand, 68% of ammonia, and 68% of orthophosphate. The 2nd-stage sand biofilters further removed 83% of suspended solids, 45% of soluble chemical oxygen demand, and 43% of ammonia via microbial decomposition and depth filtration during 1-week batch operations.