[Effect of the Influent C/P Ratio on the Nutrient Removal Characteristics of the SNEDPR System]

This study focuses on the nitrogen (N) and phosphorus (P) removal characteristics in a simultaneous nitrification-endogenous denitrification and phosphorus removal (SNEDPR) system at different influent C/P ratios. An extended anaerobic/low aerobic (dissolved oxygen:0.5-1.0 mg·L^-1) sequencing batch reactor (SBR) fed with municipal sewage was studied by adjusting different C/P ratios (10, 15, 20, 30, and 60). The experimental results show that the proper reduction of the influent C/P ratio (C/P ratio reduced from 60 to 30) enhances the competitive advantages of phosphorus-accumulating organisms (PAOs) in the SNEDPR system. The highest phosphorus removal efficiency was achieved at a C/P ratio of 30, with the anaerobic phosphorus release rate (PRR) and aerobic phosphorus uptake rate (PUR, used as P/MLSS) reaching 3.5 mg·(g·h)^-1 and 4.2 mg·(g·h)^-1 respectively, and an average effluent PO₄^3--P concentration below 0.3 mg·L^-1. The percentage of PAOs contributing to the storage of endogenesis carbon (P_{PAO, An}) reached 88.1%. However, a poor phosphorus removal performance was observed with further reduction of the influent C/P ratios to 10; both the PO₄^3--P removal efficiency and P_{PAO, An} decreased from 38.1% and 82.4% to 3.1% and 5.3%, respectively. The PRR and PUR were 0.2 mg·(g·h)^-1 and 0.24 mg·(g·h)^-1, respectively. The COD removal performance was not affected by the decreasing influent C/P ratios; the average COD removal efficiency stabilized at 85%. In addition, the nitrification performance became worse with decreasing C/P ratios (from 60 to 20) because the effluent NH₄⁺-N and NO₂^--N concentrations increased from 0 and 6.9 mg·L^-1 to 5.1 mg·L^-1 and 16.2 mg·L^-1, respectively. The nitrificaton performance recovered when the C/P ratios further decreased to 10, but the nitrite accumulation was disturbed as both the effluent NH₄⁺-N and NO₂^--N concentrations reduced to 0. The effluent NO₃^--N concentration increased from 0.08 mg·L^-1 to 14.1 mg·L^-1. The SNED efficiency first decreased from 62.1% to 36.4% and then increased to 56.4%. The advantageous competition of glycogen accumulating organisms (GAOs) improved when the influent C/P ratio was lower than 15. The enhancement of the endogenous denitrification ability of GAOs might explain the recovery denitrification performance of the system when the influent C/P ratios decreased from 20 to 10.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).