Effects of sludge pretreatment on sludge reduction in a lab-scale anaerobic/anoxic/oxic system treating domestic wastewater

The efficiency of denitrification and enhanced biological phosphorus removal in biological nutrient removal activated sludge systems is strongly dependent on the availability of appropriate carbon sources. Due to high costs of commercial compounds (such as methanol, ethanol, acetic acid, etc.) and acclimation periods (usually) required, the effective use of internal substrates is preferred. The aim of this study was to determine the effects of slowly biodegradable compounds (particulate and colloidal), as internal carbon sources, on denitrification, phosphate release/uptake and oxygen utilization for a full-scale process mixed liquor from two large wastewater treatment plants located in northern Poland. Since it is difficult to distinguish the effect of slowly biodegradable substrate in a direct way, a novel procedure was developed and implemented. Four types of one-and two-phase laboratory batch experiments were carried out in two parallel reactors with the settled wastewater without pre-treatment (reactor 1) and pre-treated with coagulation-flocculation (reactor 2). The removal of colloidal and particulate fractions resulted in the reduced process rates (except for phosphate release). The average reductions ranged from 13 % for the oxygen utilization rate during the second phase of a two-phase experiment (anaerobic/aerobic), up to 35 % for the nitrate utilization rate (NUR) during the second phase of a conventional NUR measurement.

Section: Introductionmentioning

confidence: 99%

The role of biodegradable particulate and colloidal organic compounds in biological nutrient removal activated sludge systems

Drewnowski

Mąkinia

2013

“…Since Morgenroth et al (1997) found the aerobic sludge granulation in a sequence bioreactor, researchers have conducted numerous studies on the formation and characteristics of aerobic granule, affecting factors of sludge granulation, mass transfer and model simulation, extracellular polymeric substances (EPS), and formation mechanism (Beun et al 2002;Liu et al 2006;Wan et al 2009;de Kreuk et al 2010;Ni and Yu 2010;Gao et al 2011, Uan et al 2013. However, the aerobic granular sludge system is still not stable, and the application of this technology is faced with big bottlenecks and challenges (Winkler et al 2011;Chen et al 2007;Adav et al 2008;Liu and Tay 2008).…”

Section: Introductionmentioning

confidence: 99%

Microbial community analysis for aerobic granular sludge reactor treating high-level 4-chloroaniline wastewater

Zhu

Dai

et al. 2013

A laboratory-scale sequencing airlift bioreactor continuously treating high-level 4-chloroaniline (4-ClA) wastewater was used for studying the effect of 4-ClA on the characteristics and microbial community of aerobic granular sludge. The granulation of aerobic sludge and efficient pollutant removal performance were developed via shortening sludge settling time and gradually increasing influent 4-ClA concentration to around 400 mg L -1 . However, the granular sludge reactor deteriorated with the 4-ClA loading rate above 0.8 kg m -3 d -1 . Denaturing gradient gel electrophoresis and real-time quantitative PCR were applied to investigate the microbial community succession during the start-up and recovery of bioreactor. The results showed that the performance of granular reactor was significantly influenced by the microbial community of aerobic granule, and stable aerobic granule was dominated with b-Proteobacteria (61.28 %), Flavobacteriales, Planctomycetales, Clostridiales, and Acidobacteria. Since Thauera (21.55 %) related to the genus b-Proteobacteria was abundant in the stable 4-ClA-degrading granular sludge, it was speculated as the main 4-ClA-degrading bacteria. Under high chloroaniline level, the sludge granulation may maintain the stability of the bioreactor via adjusting the composition of microbial community and abundance of functional microorganism. This paper provided useful information for better understanding the change of microbial community characteristics under highlevel toxic organic pollutants and process optimizing.

“…The recovery rate, concentrate grade and separation efficiency are selected as the main indicators to evaluate the separation results (Raj et al 2013;Uan et al 2013;Uma Rani et al 2013). The separation efficiency could be calculated as Eq.…”

Section: Particle Size Distribution Of the Crushing Waste Pcb Slotsmentioning

confidence: 99%

Recovery of valuable metal concentrate from waste printed circuit boards by a physical beneficiation technology

Chen

et al. 2014

It is greatly significant to separate precious metals from the waste printed circuit boards (PCBs) with appropriate methods for the resource recycling and environment protection. A combined physical beneficiation technology for the recovery of waste PCBs was investigated. Waste PCBs were disassembled into substrates and slots firstly. Waste PCB substrates were crushed to the size below 1 mm by a wet impact crushing approach. The double Rosin-Rammler functions were proposed to describe the particle size distribution characteristic of the substrates. The crushing products of the substrates were separated by a self-designed water-medium tapered column separation bed. The results indicate that the separation efficiency of 93.9 % and metal recovery rate of 93.7 % are obtained with a water discharge of 5.5 m 3 /h, feeding capacity of 250 g/min and inclination angle of 35°. Waste PCB slots were crushed to the size range of 0.5-5 mm by a dry impact crushing approach and separated by an active pulsing air classifier. The separation results show that a separation efficiency of 92.4 % and metal recovery rate of 96.2 % are obtained with the airflow velocity of 2.90 m/s and pulsing frequency of 2.33 Hz. The mismatching components in the metal concentrate are relatively less with suitable operating conditions. Precious metals could be obtained by the further separation and purification of metal concentrates. The technology has great potential to be applied in the field of waste PCB recycling.