Distribution characteristics of sulfonamide antibiotics between water and extracellular polymeric substances in municipal sludge.

The interaction between extracellular polymeric substances (EPS) in municipal sludge and antibiotics in wastewater is critical in wastewater treatment, resource recovery, and sludge management. Therefore, it is increasingly urgent to investigate the distribution coefficient (Log K) of sulfonamide antibiotics (SAs) in EPS, particularly in sludge-derived dissolved organic carbon (DOC) and aqueous phase systems. Herein, through balance experiments, the concentrations of SAs were determined using alkaline extraction EPS (AEPS) and alginate-like extracellular polymer (ALE) systems, and the Log KDOC values were determined. The results showed that the Log KDOC of AEPS was higher than that of ALE, which exhibited a negative KDOC value, indicating an inhibitory effect on dissolution. For the three SAs studied, the Log KDOC values were in the following order: sulfamethoxazole > sulfapyridine > sulfadiazine. This order can be attributed to the differing physicochemical properties, such as polarity, of the SAs. Three-dimensional excitation-emission matrix fluorescence spectra and fitting results indicated a lack of aromatic proteins dominated by tryptophan and humus-like substances in ALE. Meanwhile, the hydrophobic interaction of aromatic proteins dominated by tryptophan was the main driving force in the binding process between AEPS and SAs.

Occurrence and mechanism of sulfamethoxazole in alginate-like extracellular polymers from excess sludge.

The recovery of biopolymers, particularly alginate-like extracellular polymers, from municipal sludge represents a promising step toward sustainable sludge treatment practices. Originating from wastewater plants in complexly polluted environments, alginate-like extracellular polymers carry potential environmental risks concerning their reuse. This study employs ultrahigh-performance liquid chromatography-tandem mass spectrometry to investigate the distribution coefficients and occurrence of alginate-like extracellular polymers and sulfamethoxazole. Results demonstrate a negative distribution coefficient, suggesting an inhibitory effect on sulfamethoxazole dissolution. The ethanol-extracted alginate-like extracellular polymers exhibits higher sulfamethoxazole levels (approximately 52%) than those obtained via dialysis extraction. Three-dimensional excitation-emission matrix analysis and adsorption studies indicate the absence of tyrosine-like substances in the alginate-like extracellular polymers, unlike in other extracellular polymeric substances. This absence diminishes hydrophobic interactions, highlighting that electrostatic interactions play a more important role. These insights are crucial for understanding the adsorption behavior of alginate-like extracellular polymers and optimizing their large-scale extraction processes.

Concentration properties of biopolymers via dead-end forward osmosis.

Extracellular polymeric substances (EPSs) in excess sludge of wastewater treatment plants are valuable biopolymers that can act as recovery materials. However, effectively concentrating EPSs consumes a significant amount of energy. This study employed novel energy-saving pressure-free dead-end forward osmosis (DEFO) technology to concentrate various biopolymers, including EPSs and model biopolymers [sodium alginate (SA), bovine serum albumin (BSA), and a mixture of both (denoted as BSA-SA)]. The feasibility of the DEFO technology was proven and the largest concentration ratios for these biopolymers were 94.8 % for EPSs, 97.1 % for SA, 97.8 % for BSA, and 98.4 % for BSA-SA solutions. An evaluation model was proposed, incorporating the FO membrane's water permeability coefficient and the concentrated substances' osmotic resistance, to describe biopolymers' concentration properties. Irrespective of biopolymer type, the water permeability coefficient decreased with increasing osmotic pressure, remained constant with increasing feed solution (FS) concentration, increased with increasing crossing velocity in the draw side, and showed little dependence on draw salt type. In the EPS DEFO concentration process, osmotic resistance was minimally impacted by osmotic pressure, FS concentration, and crossing velocity, and monovalent metal salts were proposed as draw solutes. The interaction between reverse diffusion metal cations and EPSs affected the structure of the concentrated substances on the FO membrane, thus changing the osmotic resistance in the DEFO process. These findings offer insights into the efficient concentration of biopolymers using DEFO.

Calcium Alginate Production through Forward Osmosis with Reverse Solute Diffusion and Mechanism Analysis.

Calcium alginate (Ca-Alg) is a novel target product for recovering alginate from aerobic granular sludge. A novel Ca-Alg production method was proposed herein where Ca-Alg was formed in a sodium alginate (SA) feed solution (FS) and concentrated via forward osmosis (FO) with Ca2+ reverse osmosis using a draw solution of CaCl2. An abnormal reverse solute diffusion was observed, with the average reverse solute flux (RSF) decreasing with increasing CaCl2 concentrations, while the average RSF increased with increasing alginate concentrations. The RSF of Ca2+ in FS decreased continuously as the FO progressed, using 1.0 g/L SA as the FS, while it increased initially and later decreased using 2.0 and 3.0 g/L SA as the FS. These results were attributed to the Ca-Alg recovery production (CARP) formed on the FO membrane surface on the feed side, and the percentage of Ca2+ in CARP to total Ca2+ reverse osmosis reached 36.28%. Scanning electron microscopy and energy dispersive spectroscopy also verified CARP existence and its Ca2+ content. The thin film composite FO membrane with a supporting polysulfone electrospinning nanofiber membrane layer showed high water flux and RSF of Ca2+, which was proposed as a novel FO membrane for Ca-Alg production via the FO process with Ca2+ reverse diffusion. Four mechanisms including molecular sieve role, electrification of colloids, osmotic pressure of ions in CARP, and FO membrane structure were proposed to control the Ca-Alg production. Thus, the results provide further insights into Ca-Alg production via FO along with Ca2+ reverse osmosis.

[N2O Emission from the Processes of Wastewater Treatment: Mechanisms and Control Strategies].

As a direct carbon emission source, the amount of nitrous oxide (N2, which is actually caused by AOB denitrification. To control the N2O emission during biological N-removal, complete HND and NO2- accumulation for AOB denitrification should be avoided to a large extent. For this purpose, DO in aerobic tanks should be controlled at a normal level (approximately 2 mg·L-1), and solid retention time (SRT) should be extended, up to 20 d, which would avoid accumulating N2O for AOB denitrification. Additionally, external carbon should be supplemented in time to promote HDN approaching the end, N2. This review summarizes the mechanisms of all the mentioned N2O emission pathways and discusses the control strategies of N2O emission according to the associated mechanisms.

Recovery of Extracellular Polymeric Substances from Excess Sludge Using High-Flux Electrospun Nanofiber Membranes.

The recycling of extracellular polymeric substances (EPSs) from excess sludge in wastewater treatment plants has received increasing attention in recent years. Although membrane separation has great potential for use in EPS concentration and recovery, conventional membranes tend to exhibit low water flux and high energy consumption. Herein, electrospun nanofiber membranes (ENMs) were fabricated using polyvinylidene fluoride (PVDF) and used for the recovery of EPSs extracted from the excess sludge using the cation exchange resin (CER) method. The fabricated ENM containing 14 wt.% PVDF showed excellent properties, with a high average water flux (376.8 L/(m2·h)) and an excellent EPS recovery rate (94.1%) in the dead-end filtration of a 1.0 g/L EPS solution at 20 kPa. The ENMs displayed excellent mechanical strength, antifouling properties, and high reusability after five recycles. The filtration pressure had a negligible effect on the average EPS recovery rate and water flux. The novel dead-end filtration with an EPS filter cake on the ENM surface was effective in removing heavy-metal ions, with the removal rates of Pb2+, Cu2+, and Cr6+ being 89.5%, 73.5%, and 74.6%, respectively. These results indicate the potential of nanofiber membranes for use in effective concentration and recycling of EPSs via membrane separation.

Extracting compositional blocks of alginate-like extracellular polymers (ALE) from conventional activated sludge (CAS).

As a highly added value material, alginate-like extracellular polymers (ALE) can be extracted from extracellular polymeric substances (EPS) from aerobic granular sludge (AGS). In fact, conventional activated sludge (CAS) also contains a certain amount of ALE. As CAS is widely used everywhere, waste activated sludge (WAS) from CAS is huge in its absolute amount. Although the ALE property of CAS was identified not so good as that from AGS, the mechanisms remains unclear. For this reason, it is necessary to unravel the chemically compositional blocks of ALE. Referring to natural alginate, ALE can be separated into three compositional blocks: GGL, GML and MML (like units containing guluronate or mannuronate), associated with other compositions including protein (PN), polysaccharide (PS), phosphorus (P), humic acid (HA). With real WAS from CAS, ALE was extracted and three blocks were separated: GGL = 54 %, GML = 42 % and MML = 4 % in weight, which is similar to the previous study. Moreover, the GGL blocks in CAS were obviously lower than AGS, down to by 1/3-1/2. And the GML and MML blocks in CAS were much higher than AGS, by more than 1/2. Different compositional blocks of ALE in AGS and CAS should be the reason forming different properties in applications. For this reason, a further study will be initiated to dispense/reorganize three blocks of ALE from CAS for expanding its potential applications, based on the compositional blocks of ALE from AGS.

Association Between Insulin Resistance and Remote Diffusion-Weighted Imaging Lesions in Primary Intracerebral Hemorrhage.

Background: Abnormal glucose metabolism was shown to be associated with the occurrence of remote diffusion-weighted imaging lesions (R-DWILs) after primary intracerebral hemorrhage (ICH) onset. Insulin resistance is a metabolic disorder that was regarded as an indicator of chronic systemic inflammation. In this study, we aimed to determine the effect of insulin resistance on the occurrence of R-DWILs in ICH. Methods: Patients with primary ICH within 14 days after onset were prospectively enrolled from November 2017 to October 2019. R-DWILs was defined as remote focal hyperintensity from the hematoma in DWI, with corresponding hypointensity in apparent diffusion coefficient. The homeostasis model assessment of insulin resistance (HOMA-IR) was used for insulin resistance estimation and calculated as fasting insulin (µU/ml) × fasting glucose (mmol/L)/22.5. Patients in our cohort were divided into four groups according to HOMA-IR index quartiles. Logistic regression analysis and smoothing plots were used to evaluate the association of HOMA-IR with R-DWIL occurrence. Sensitivity analysis was performed in non-diabetic patients, non-obese patients, hypertensive ICH patients, and patients 60 years and older separately. The association between HOMA-IR and systemic inflammatory immune indices neutrophil to lymphocyte ratio (NLR) and monocyte to lymphocyte ratio (MLR) was examined with multiple linear regression analysis. Results: Among the 345 patients, 54 (15.7%) had R-DWILs. Both the third and fourth quartiles of HOMA-IR index were robustly associated with an increased risk of R-DWIL occurrence (adjusted OR 3.58, 95% CI 1.33-9.65; adjusted OR 3.91, 95%CI 1.47-10.41) when compared with the first quartile. The association was consistent in non-diabetic, non-obese, hypertensive ICH patients, as well as in patients 60 years and older. Furthermore, both NLR and MLR were independently associated with HOMA-IR. Conclusions: Our study suggested that insulin resistance evaluated with HOMA-IR index was independently associated with the presence of R-DWILs in patients with acute and subacute primary ICH. It may provide new insights into the metabolism-related brain injury after ICH ictus.

News on alginate recovery by forward osmosis: Reverse solute diffusion is useful.

The water content in the recycled alginate solutions from aerobic granular sludge was nearly 100%. Forward osmosis (FO) has become an innovative dewatering technology. In this study, the FO concentration of sodium alginate (SA) was investigated using calcium chloride as a draw solute. The reverse solute flux (RSF) of calcium ions in FO had a beneficial effect, contrary to the findings of previous literature. The properties of the concentrated substances formed on the FO membrane on the feed side were analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, verifying that calcium alginate (Ca-Alg), which can be used as a recycled material, was formed on the FO membrane on the feed side owing to the interaction between SA and permeable calcium ions. Water flux increased significantly with the increase in calcium chloride concentration, while the concentration of SA had little influence on the water flux in FO. Based on this discovery, we propose a novel method for the concentration and recovery of alginate, in which the RSF of calcium ions is utilized for recovering Ca-Alg by FO, with calcium chloride as a draw solute.

Recovery of polymeric substances from excess sludge: Surfactant-enhanced ultrasonic extraction and properties analysis.

The recovery of polymeric substances from excess sludge is gaining significant research interest in future wastewater treatment technologies. We present a surfactant-enhanced ultrasonic method to extract mixed polymeric substances with typical functional groups from excess sludge. Four potential reasons were revealed for the higher efficiency upon ultrasonication with surfactant: low surface tension, damage of non-covalent bonds between extracellular polymeric substances and cells, enhanced dissolution of polymeric substances, and release of intracellular polymeric substances caused by cell lysis. The increase in extraction efficiency after the addition of cetyltrimethylammonium bromide and sodium dodecyl sulfate reached the maximum of 76.5% and 53.1%, respectively. The contents of polysaccharides, proteins, and DNA were approximately 50% of the total polymeric substances, and the content of protein was higher than that of polysaccharide; the concentration change of the surfactant had a minimal effect on these contents. For the polymeric substances extracted via ultrasonication with surfactant, the size was smaller than that for the non-surfactant extraction; moreover, the contents of metals decreased significantly (Al: 0.18% → 0%; Na: 0.15% → 0%; Ca: 0.24% → 0.11%), which was probably caused by the interaction between the surfactant and metal ions in the excess sludge. The surfactant had a negligible effect on the properties of polymeric substances, adsorption capacity of polymeric substances for heavy metal ions, and dewatering performance of sludge. The recycled polymeric substances may be used as a substitute for commercial adsorbents of heavy metal ions. Thus, the obtained results provide further insight into the recovery of polymeric substances from excess sludge via the surfactant-enhanced ultrasonic method.

[Mechanisms Summary and Potential Analysis of EPS as a Flame Retardant].

High value-added extracellular polymer substance (EPS) extracted from excess sludge can effectively promote resource recovery from wastewater. EPS can replace traditional alginate in the food, medicine, textile, printing and dyeing, papermaking, and household chemicals industries. Moreover, its unique performance as a flame retardant has shown attractive potential for aircraft including space shuttles. This is due to the complicated chemical structure and composition of EPS, the excellent compatibility, adhesion, and other advantages of which could yield environmental-friendly flame-retardants. Therefore, a systematic analysis and summary on the mechanisms of EPS as flame retardants is of significance for future application. On the basis of the advantages and disadvantages of other fire-resistant materials on the market, the characteristics and application potential of EPS are analyzed and summarized. Second, the possible fire-resistant mechanisms of phosphorus and alginate-like substance (ALE) in EPS are revealed, and the synergistic flame-retardant effects of extracellular-proteins are also elucidated. Based on this, the flame-retardant characteristics of EPS are comprehensively evaluated and compared with other fire-resistant materials. To further improving the performance of EPS as a flame-retardant material, some modification strategies are proposed, such as increasing their phosphorus content, purifying and enhancing the content of ALE in EPS, and optimizing the modification methods of EPS on their substrates.

Separation of trace pharmaceuticals individually and in combination via forward osmosis.

With a high rejection coefficient for trace pharmaceuticals and personal care products (PPCPs), forward osmosis (FO) membrane separation has become a cutting-edge technology in water treatment owing to its low energy consumption and low membrane fouling. Wastewater contains many types of PPCPs, and one pharmaceutical molecule affects the separation behaviors of other pharmaceuticals in FO. Therefore, simultaneous FO of multiple PPCPs needs to be investigated. In this study, the separation behaviors of four trace pharmaceuticals (ciprofloxacin (CIP), sulfamethoxazole (SMX), acetaminophen (ACP), carbamazepine (CBZ)), individually (termed "single pharmaceuticals") and in combination (termed "binary pharmaceuticals" as two pharmaceuticals were studied simultaneously), during FO were investigated at trace concentrations using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that for single pharmaceuticals, the molecular sieve dominates their retention rate-the retention rate increases with increasing Stokes radius of the molecules (29.1 â†’ 94.8% for 0.35 â†’ 0.47 nm). For binary pharmaceuticals, the retention rates of both pharmaceuticals without charge decrease with increasing total molecule number (for ACP + CBZ, 31.4 â†’ 52.1% (ACP), 75.1 â†’ 83.0% (CBZ)). Negatively charged pharmaceuticals are mutually exclusive with the negatively charged FO membrane, resulting in the increase of the retention rate of pharmaceuticals (83.1 â†’ 90.1% (CIP) when CIP + ACP â†’ CIP + SMX). In the presence of a positively charged pharmaceutical, the retention rate of negatively charged pharmaceuticals decreases (85.7 â†’ 80.4% (SMX) when SMX + ACP â†’ SMX + CIP) because the positively charged pharmaceutical neutralizes the negative charge on the FO membrane surface, resulting in the weakening of electrostatic repulsion between the negatively charged pharmaceutical and FO membrane surface. The positively charged molecule attracts the negatively charged molecule, forming a couple of molecules with larger molecule weight and increasing the retention rate of the pharmaceuticals (80.4 â†’ 88.2% (SMX) when pH = 7 â†’ 5 for SMX + CIP). The results suggest that the interactions between pharmaceuticals cannot be ignored in the process of removing PPCPs by FO.

CD200Fc Improves Neurological Function by Protecting the Blood-brain Barrier after Intracerebral Hemorrhage.

CD200 is widely distributed in the central nervous system and plays an essential role in the immune response in neurological diseases. However, little is currently known about the effects of CD200 signaling on the blood-brain barrier (BBB) function after intracerebral hemorrhage (ICH). In this study, the role of CD200 during ICH in an autologous blood induced mouse ICH model was investigated. Following ICH, critical protein expression, BBB permeability, and neurological function were measured with or without CD200Fc administration. Our results showed that both the expression of CD200 and CD200R1 decreased after ICH and administration of CD200Fc attenuated BBB leakage and improved neurological functions. In conclusion, our work demonstrated that CD200Fc might be a potential treatment option for ICH by protecting the BBB and improving functional outcomes.

Thrombin disrupts vascular endothelial-cadherin and leads to hydrocephalus via protease-activated receptors-1 pathway.

AIMS: Previous studies indicated that intraventricular injection of thrombin would induce hydrocephalus. But how thrombin works in this process remains unclear. Since cadherin plays a critical role in hydrocephalus, we aimed to explore the mechanisms of how thrombin acted on choroid plexus vascular endothelium and how thrombin interacted with vascular endothelial-cadherin (VE-cadherin) during hydrocephalus. METHODS: There were two parts in this study. Firstly, rats received an injection of saline or thrombin into the right lateral ventricle. Magnetic resonance imaging was applied to measure the lateral ventricle volumes. Albumin leakage and Evans blue content were assessed to test the blood-brain barrier function. Immunofluorescence and Western blot were applied to detect the location and the expression of VE-cadherin. Secondly, we observed the roles of protease-activated receptors-1 (PAR1) inhibitor (SCH79797), Src inhibitor (PP2), p21-activated kinase-1 (PAK1) inhibitor (IPA3) in the thrombin-induced hydrocephalus, and their effects on the regulation of VE-cadherin. RESULTS: Our study demonstrated that intraventricular injection of thrombin caused significant downregulation of VE-cadherin in choroid plexus and dilation of ventricles. In addition, the inhibition of PAR1/p-Src/p-PAK1 pathway reversed the decrease of VE-cadherin and attenuated thrombin-induced hydrocephalus. CONCLUSIONS: Our results suggested that the thrombin-induced hydrocephalus was associated with the inhibition of VE-cadherin via the PAR1/p-Src/p-PAK1 pathway.

Dopamine neuron loss by selective deletion of autophagy-related gene 5 is not exacerbated by MPTP toxicity in midbrain.

Parkinson's disease (PD) is a progressive neurological disease, one of the pathological characteristics is a gradual loss of midbrain dopaminergic (mDA) neurons in the substantia nigra pars compacta (SNpc). In animals, PD-like symptoms can be induced by genetic mutations or by neurotoxins such as 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). It has been reported that deletion of autophagy-related gene 5 (Atg5) in the brain can disrupt neural function and is accompanied by the accumulation of cytoplasmic inclusions. However, the exact role of autophagy in PD etiology has not fully been asserted. In this study, we used tyrosine hydroxylase (TH)-Cre mice to generate conditional knockouts (CKO) with the specific deletion of Atg5 in mDA neurons, and found that adult Atg5 CKO mice contained ubiquitin- and p62-positive inclusions and fewer TH-positive mDA neurons compared with wild-type controls. Interestingly, MPTP-induced loss of mDA neurons was not observed in Atg5 CKO mice. Thus, Atg5-associated autophagy is required for the survival of mDA neurons, and may be involved in MPTP-induced neuronal degeneration.

[Enriched experiment and endogenous processes of glycogen-accumulating organisms (GAOs)].

Cell decay is an important part of microbiological endogenous processes, which consists of cell death (reduction in the amount of active bacteria) and activity decay (reduction in the specific activity of active bacteria). By means of measuring maximal anaerobic volatile fatty acid (VFA) uptake rates (VFAUR), analyzing 16S rRNA with fluorescence in-situ hybridization (FISH) and observing membrane integrity by live/dead staining, the aerobic decay characteristics of glycogen-accumulating organisms (GAOs) in an enriched GAOs sequencing batch reactor (SBR) system were investigated. It was experimentally identified that a highly enriched culture of GAOs (94%) was obtained by maintaining the temperature at 30 degrees C in the SBR and a high m (COD): m (P) at 100 in the feed. The experimental results and calculations revealed that the decay and death rates of GAOs were 0.132 d(-1) and 0.034 d(-1) respectively, which demonstrated that cell death and activity decay accounted for respective 26% and 74% of the total GAOs cell decay. For this reason, cell death was only a minor factor causing the cell decay of GAOs, and activity decay was mostly responsible for this process.

[Making optimal operation for a BNR process: modeling prediction and experimental verification].

Based on the process model of a BNR system (BCFS), the effects of operational parameters on the effluent quality were predicted by modeling, and were testified simultaneously by a lab-scale experiment, from which almost the same results in the modeling and the experiment were obtained. This means that modeling can be realizably applied to make the optimal operation schemes regardless of pilot-scale and/or full-scale experiments. Both the modeling and the experiment demonstrated that the bio-P removal performance was not influenced by the biomass amount in the anaerobic tank when the returned ratio (rA ) reached 1.5 and that rA had no significant correlation with COD and N removals. After the returned mixed liquor ratio (rB) increased over 2, the TN removal efficiency was not improved any more, and the COD and TP removals were not influenced by the variations of the rB. The returned mixed liquor ratio rC had almost no influences on the COD, TP and TN removals. Further, the COD and TP removals were not influenced when the dissolved oxygen (DO(R5)) in the aerobic tank was in the range of 1-2.5 mg x L(-1), but the effluent NH4+ -N increased over 1 mg x L(-1) when DO(R5 ) was below 2 mg x L(-1). So, the optimal operational parameters for the BCFS should be set at rA = 2, rB 2-2.5, rC = 0, DO(R5) 2-2.5 mg x L(-1).

[Optimal formation conditions and analytical methods of the target product by MAP precipitation].

In order to establish optimal conditions of the struvite (MAP: MgNH4PO4 x 6H2O) formation, acid dissolution was applied and developed to perform element analyses on the precipitates obtained from MAP precipitation, and a novel analyzing and calculating method was developed to quantitatively determine the struvite content (purity) in the harvested precipitates according to the NH4+-N content. With this method, the purities of struvite were respectively determined for both ultra pure water and tap water used as solutes. At the same time, the effect of pH and Ca2+ on the formation and crystallization of struvite was evaluated. The newly developed method was effective enough to determine the purities of struvite, which could be a better method than qualitative X-ray diffraction (XRD). Based on the developed method, it was found that the optimal pH ranges for having a high struvite content (> 90%) were respectively at 7.5-9.0 with ultra pure water as solute and at 7.0-7.5 with tap water as solute. In real wastewater, Ca2+ at pH > 8.0 might result in impurities rather than struvite. Therefore, a neutral pH range (< 8.0) is proposed to perform struvite precipitation in wastewater.

[Experimental study on the effect of COD/P ratios and phosphate recovery on a BNR system].

Based on a BNR system--BCFS, the effect of COD/P and phosphate recovery on the BCFS process was experimentally investigated. The results indicate that a higher P-removal efficiency (87%) and a good P-effluent quality (< or = 0.8 mg x L(-1)) could be maintained at COD/P ratios higher than 24. When COD/P was reduced below 24, the P-removal efficiency was suddenly decreased down to 62% and the P-effluent went up to 5 mg x L(-1). Under the circumstance, chemical phosphate recovery in the side-stream of anaerobic supernatant was combined with bio-P removal. When the side-stream increased up to 30%, the P-effluent went back to < 1 mg x L(-1), with a corresponding phosphate recovery efficiency of 54%.

[Experimental determination of bacterial decay characteristics in biological wastewater treatment system].

The characteristics of cell decay in biological wastewater treatment systems were investigated under aerobic condition, by measuring the decay rate and by determining the death rate with LIVE/DEAD dyeing experiments. It was found that cell decay in biological wastewater treatment systems can be actually described as two parts: decay caused by cell death and decay derived from activity decrease. The experimental results revealed that 60% of cell decay in a nitrifying system was caused by activity decrease and 40% was caused by cell death. In a heterotrophic system, however, activity decrease was responsible for 80% of cell decay, and the other cell decay for 20% was caused by cell death.