The effects of a full-scale anaerobic side-stream reactor on sludge decay and biomass activity.

A full-scale anaerobic side-stream reactor (ASSR) for sludge reduction was monitored in terms of sludge production and compared with the previous conventional activated sludge configuration (CAS). A detailed solid mass balance was calculated on the whole full-scale plant to estimate the sludge reduction associated with the ASSR. The activity of the biomass, which undergoes alternation of aerobic and anaerobic conditions, was investigated by the respirometric test. The ASSR promoted a reduction of heterotrophic biomass activity and the substrate consumption rate in the activated sludge implemented with ASSR (AS + ASSR) was 36% smaller than in the CAS period. The solid mass balance indicated a sludge reduction of 28%. During the 270-day operation, the observed sludge yield passed from 0.438 kgTSS/kgCOD in the CAS to 0.315 in the AS + ASSR configuration. The solubilization of chemical oxygen demand (COD), NH4 +-N and orthophosphate were verified under anaerobic conditions. The results suggest that the possible mechanisms of sludge reduction were the increase of the system sludge retention time (SRT) by ASSR addition, and the reduction in heterotrophic biomass activity added to the organic compounds' hydrolysis.

Effect of COD/N ratio on N2O production during nitrogen removal by aerobic granular sludge.

N2O-production was investigated during nitrogen removal using aerobic granular sludge (AGS) technology. A pilot sequencing batch reactor (SBR) with AGS achieved an effluent in accordance with national discharge limits, although presented a nitrite accumulation rate of 95.79% with no simultaneous nitrification-denitrification. N2O production was 2.06 mg L-1 during the anoxic phase, with N2O emission during air pulses and the aeration phase of 1.6% of the nitrogen loading rate. Batch tests with AGS from the pilot reactor verified that at the greatest COD/N ratio (1.55), the N2O production (1.08 mgN2O-N L-1) and consumption (up to 0.05 mgN2O-N L-1), resulted in the lowest remaining dissolved N2O (0.03 mgN2O-N L-1), stripping the minimum N2O gas (0.018 mgN2O-N L-1). Conversely, the carbon supply shortage, under low C/N ratios, increased N2O emission (0.040 mgN2O-N L-1), due to incomplete denitrification. High abundance of ammonia-oxidizing and low abundance of nitrite-oxidizing bacteria were found, corroborating the fact of partial nitrification. A denitrifying heterotrophic community, represented mainly by Pseudoxanthomonas, was predominant in the AGS. Overall, the AGS showed stable partial nitrification ability representing capital and operating cost savings. The SBR operation flexibility could be advantageous for controlling N2O emissions, and extending the anoxic phase would benefit complete denitrification in cases of low C/N influents.

Anaerobic side-stream reactor for excess sludge reduction: 5-year management of a full-scale plant.

The long-term performances of a full-scale anaerobic side-stream reactor (ASSR) aimed at sludge reduction have been monitored for the first time, in comparison with a conventional activated sludge process (CAS). The plant was integrated with an ASSR treatment of 2293-3293 m(3). Operational parameters in the ASSR were: ORP -250 mV, interchange ratio of 7-10%, hydraulic retention time of 7 d. No worsening of effluent quality was observed in the ASSR configuration and removal efficiency of COD and NH4 was above 95%. A slight increase in the Sludge Volume Index did not cause worsening in effluent solids concentration. The observed sludge yield (Yobs) passed from 0.44 kgTSS/kgCOD in the CAS to 0.35 in the ASSR configuration. The reduction of Yobs by 20% is lower than expected from the literature where sythetic wastewater is used, indicating that sludge reduction efficiency is largely affected by inert mass fed with influent real wastewater. An increase by 45% of the ASSR volume did not promote a further reduction of Yobs, because sludge reduction is affected not solely by endogenous decay but also by other factors such as interchange ratio and aerobiosis/anaerobiosis alternation.

Valuation of OSA process and folic acid addition as excess sludge minimization alternatives applied in the activated sludge process.

The aim of this study was to investigate the ability of the oxic-settling-anaerobic (OSA)-process and the folic acid addition applied in the activated sludge process to reduce the excess sludge production. The study was monitored during two distinct periods: activated sludge system with OSA-process, and activated sludge system with folic acid addition. The observed sludge yields (Yobs) were 0.30 and 0.08 kgTSS kg(-1) chemical oxygen demand (COD), control phase and OSA-process (period 1); 0.33 and 0.18 kgTSS kg(-1) COD, control phase and folic acid addition (period 2). The Yobs decreased by 73 and 45% in phases with the OSA-process and folic acid addition, respectively, compared with the control phases. The sludge minimization alternatives result in a decrease in excess sludge production, without negatively affecting the performance of the effluent treatment.

Concerning the role of cell lysis-cryptic growth in anaerobic side-stream reactors: the single-cell analysis of viable, dead and lysed bacteria.

In the Anaerobic Side-Stream Reactor (ASSR), part of the return sludge undergoes alternating aerobic and anaerobic conditions with the aim of reducing sludge production. In this paper, viability, enzymatic activity, death and lysis of bacterial cells exposed to aerobic and anaerobic conditions for 16 d were investigated at single-cell level by flow cytometry, with the objective of contributing to the understanding of the mechanisms of sludge reduction in the ASSR systems. Results indicated that total and viable bacteria did not decrease during the anaerobic phase, indicating that anaerobiosis at ambient temperature does not produce a significant cell lysis. Bacteria decay and lysis occurred principally under aerobic conditions. The aerobic decay rate of total bacteria (bTB) was considered as the rate of generation of lysed bacteria. Values of bTB of 0.07-0.11 d(-1) were measured in anaerobic + aerobic sequence. The enzymatic activity was not particularly affected by the transition from anaerobiosis to aerobiosis. Large solubilisation of COD and NH4(+) was observed only under anaerobic conditions, as a consequence of hydrolysis of organic matter, but not due to cell lysis. The observations supported the proposal of two independent mechanisms contributing equally to sludge reduction: (1) under anaerobic conditions: sludge hydrolysis of non-bacterial material, (2) under aerobic conditions: bacterial cell lysis and oxidation of released biodegradable compounds.

Congenital orbital teratoma up to posterior fossa.

Congenital orbital teratoma is a rare condition which presents as marked proptosis of eyeball in a newborn. It is rapidly progressive with secondary damage to eyeball due to pressure effect. This case presented by us is of interest due to radiological features and rarity of this tumor extending into posterior fossa.

Consortia of microalgae and bacteria in the performance of a stabilization pond system treating landfill leachate.

This study treated sanitary landfill leachate and was conducted in a pilot-scale system composed of three serial ponds (P1, P2 and P3), followed by a rock filter, in order to evaluate the microbial consortium influence on system performance and to investigate microorganism dynamics in the process. The system was broken into three stages, with a continuous flow rate (Q = 200 L d⁻¹) for 43 weeks. The stages were as follows: conventional operation (stage I), 12 h aeration in P2 (stage II), and 18 h aeration in P2 (stage III). The results showed the possibilities for treating landfill leachate, presenting an average efficiency of 75% for both filtered biochemical oxygen demand and ammonium. At the end of stage III, the ammonium concentration was 6 mg L⁻¹, which is lower than that established by Brazilian regulations for wastewater discharge (CONAMA 430/2011). The aeration applied in P2 led to a change in the microbial consortia during the second and third stage, which influenced the quality of the final effluent. The best performance was seen in stage III, where the system showed high microbial diversity, including the presence of nitrifying bacteria.

Nutrient recovery from swine waste and protein biomass production using duckweed ponds (Landoltia punctata): southern Brazil.

Brazil is one of the most important countries in pork production worldwide, ranking third. This activity has an important role in the national economic scenario. However, the fast growth of this activity has caused major environmental impacts, especially in developing countries. The large amount of nitrogen and phosphorus compounds found in pig manure has caused ecological imbalances, with eutrophication of major river basins in the producing regions. Moreover, much of the pig production in developing countries occurs on small farms, and therefore causes diffuse pollution. Therefore, duckweed pond have been successfully used in the swine waste polishing, generating further a biomass with high protein content. The present study evaluated the efficiency of two full scale duckweed ponds for the polishing of a small pig farm effluent, biomass yield and crude protein (CP) content. Duckweed pond series received the effluent from a biodigester-storage pond, with a flow rate of 1 m(3)/day (chemical oxygen demand rate = 186 kg/ha day) produced by 300 animals. After 1 year a great improvement of effluent quality was observed, with removal of 96% of total Kjeldahl nitrogen (TKN) and 89% of total phosphorus (TP), on average. Nitrogen removal rate is one of the highest ever found (4.4 g TKN/m(2) day). Also, the dissolved oxygen rose from 0.0 to 3.0 mg/L. The two ponds produced together over 13 tons of fresh biomass (90.5% moisture), with 35% of CP content, which represents a productivity of 24 tonsCP/ha year. Due to the high rate of nutrient removal, and also the high protein biomass production, duckweed ponds revealed, under the presented conditions, a great potential for the polishing and valorization of swine waste. Nevertheless, this technology should be better exploited to improve the sustainability of small pig farms in order to minimize the impacts of this activity on the environment.

Diagnostic dilemma in a case of early spinal tumour fracture (Plasmacytoma): a case report.

MRI findings of D12 fracture were suspicious of a pathological fracture. However, biopsy did not show any evidence of tumour. This resulted in the patient following up after one and half years with an epidural mass lesion and neurological deterioration. This paper highlights some of the MRI features of fractures associated with underlying pathology over traumatic or osteoporotic fracture.

[Successful operation of aortic abscess ruptured into left atrium. Diagnostic importance of color coded Doppler echocardiography]. / Abcesso aórtico com rotura para a aurícula esquerda, operado com sucesso. Importância diagnóstica do eco-Doppler codificado a cor.

Myocardial abscesses are a serious complication of infectious endocarditis. A 60 years old male patient with subaortic ring abscess is reported. A fistula developed between the left ventricular outflow tract and the left atrium. Doppler echocardiography was of outmost importance for diagnosis. Surgery was successfully performed.

[Floating thrombus in the left atrium. Apropos of a clinical case]. / Trombo "flutuante" na aurícula esquerda. A propósito de um caso clínico.

The authors report a case of floating left atrial thrombus, detected by transthoracic echocardiography, in a 63 years old patient with moderate mitral stenosis and atrial fibrillation. He was admitted to hospital, with supraventricular tachyarrhythmia and pulmonary edema. There was no previous syncope or thromboembolism episodes. Apparently the anticoagulant therapy wasn't interrupted. The diagnosis of the free floating left atrial thrombus was made by two-dimensional echocardiography. Predisposing factors, clinical course and echocardiographic diagnosis are discussed. The risk of prolonged engagement of the thrombus in the mitral orifice, causing syncope or sudden death, justifies urgent surgery associating thrombectomy and treatment of mitral stenosis.