Sewage Sludge Management at District Level: Reduction and Nutrients Recovery via Hydrothermal Carbonization.

In this study, two scenarios of a municipal wastewater treatment plant (WWTP) are presented, which include the integration of the hydrothermal carbonization (HTC) process into the sludge line as a post-treatment of the anaerobic digestion (AD) process. The objective of the simulation is to investigate the performances of AD + HTC treatment to reduce sludge production and improve nutrient and energy recovery. For this purpose, the scheme of an under-construction WWTP was considered, named Trento 3 (Trento, Italy) and with a treatment capacity of 300,000 PE. In the first scenario, the HTC process was fed with thickened sludge from the Trento 3 WWTP, while in the second scenario, dewatered sludge from other local WWTPs was also used as feedstock for the HTC process. Both scenarios allowed to obtain a considerable sludge reduction ranging from 70 to 75% with a notably increase in the biogas production up to 47%, due to the recycling of HTC liquor (HTCL) to the anaerobic digester. Considering nutrients recovery, all the phosphorus and nitrogen present in the HTCL could be used for struvite precipitation with an average yearly gain of 1 million euros. Moreover, the introduction of HTC in the Trento 3 WWTP could allow a reduction in the sludge management costs of up to 2 M€/year.

Mathematical modelling of an intermittent anoxic/aerobic MBBR: Estimation of nitrification rates and energy savings.

This study aimed at modelling the performance of a novel MBBR configuration, named A/O-MBBR, comprised of a pre-anoxic reactor, with an HRT of 4.5 h, coupled with an intermittent anoxic/aerobic MBBR (HRT = 6.8 h). The lab-scale system was fed with municipal wastewater with an average influent Total Ammonia Nitrogen (TAN) and total COD (TCOD) concentrations of 46 mg of TAN-N L-1 and 310 mg TCOD L-1. During the whole experimental period, TAN removal efficiency was always higher than 96%; denitrification was also very effective, achieving nitrate and nitrite concentrations in the effluent both lower than 5 mg NOx-N L-1 on average. Moreover, TCOD average removal efficiency was equal to 85%. Modelling was performed to investigate the nitrification efficacy enhancement; to this aim, a biofilm model was developed, adopting the equations for mixed-culture biofilms and the Activated Model Sludge n°1 (ASM1) for the biological processes rates. The model allowed to determine the maximum uptake rate for autotrophic growth (µA was 2.5 d-1) and the semisaturation constant (KOA was 0.2 mg O2 L-1), suggesting that the nitrification process was 3-fold faster than average and very effective at low oxygen concentrations. The model estimated that about 85% of TAN was removed by the biofilm and only the remaining part by suspended biomass in the bulk liquid. Finally, it was assessed that the A/O-MBBR configuration allowed for a 45-60% savings of the energy requirement compared to a Benchmark WWTP layout.

Application of real-time nitrogen measurement for intermittent aeration implementation in a biological nitrogen removal system: performances and efficiencies.

Several automatic strategies for aeration control have been investigated so far to favor a significant decrement of energy consumptions in biological processes in wastewater treatment plants (WWTPs). Above all, the intermittent aeration process has demonstrated to have several advantages. This work reports the results of a case study made in a small municipal WWTP where an intermittent aeration control strategy based on the online measurement of real-time nitrogen forms has been implemented to optimize the nitrogen removal and the energy consumption in an activated process. High organic removal efficiency was achieved during the whole experimental period. Results indicated that nitrogen removal efficiency has been improved, especially during winter months, by the control strategy adopted that helped to determine the perfect length for the nitrification and denitrification phases. The intermittent aeration process increased the activity of the biomass, further selecting phosphate-accumulating bacteria and improving the growth of bacteria able to internally store carbon source. Excellent effects were achieved on energy and chemical consumption, with a reduction of about 15% and 23%, respectively. Finally, a 12% reduction of sludge production was also detected.

Progress toward full scale application of the anaerobic side-stream reactor (ASSR) process.

In order to reduce the investment costs of the anaerobic side-stream reactor (ASSR) process coupled with an activated sludge system and promote the full scale application, the impact of 1 d anaerobic solid retention time (SRTASSR) and 100% interchange ratio (IR) has been investigated on sludge reduction, carbon and nutrient removal efficiency and microbial community, in a sequencing batch reactor (SBR)-ASSR system. The SBR-ASSR achieved good removal efficiencies in COD (91.5 ±â€¯3.4%), ammonium nitrogen (98.8 ±â€¯0.5%), total nitrogen (87.9 ±â€¯4.9%) and phosphate (92.8 ±â€¯6.7). The sludge yield of the system was 0.1648 g TSS g-1COD; 54% lower compared to a conventional activated sludge (CAS) system. Real time quantitative polymerase chain reaction (q-PCR) showed an abundance of hydrolyzing and fermentative bacteria. Comparison at class and genus level confirmed an abundance of anaerobic hydrolyzing and fermentative bacteria, denitrifying bacteria able to simultaneous perform nitrogen and phosphate removal and phosphate accumulating organisms.

[Long-term development of chronic hepatitis caused by virus B in childhood]. / L'evoluzione a distanza dell'epatite cronica da virus B in età pediatrica.

Ten children with chronic hepatitis B have been followed for at least 3 years. All patients received 2 liver biopsies, the first after 1 year of continuous liver disfunction and HBsAg positivity, and the second 2 years after, that showed a mild improvement of the histologic lesions in 4 cases of chronic persistent hepatitis (CPH) and in 1 case of chronic lobular hepatitis (CLH). Three children out of 5 with chronic active hepatitis (CAN) changed to CPH and the other 2 remained unchanged without any evidence of cirrhosis. No patient received any drug for the treatment of hepatitis.

[Intra-familial transmission of HBV infection]. / La diffusione intrafamiliare dell'infezione da HBV.

We investigated 63 household contacts of 29 children positive for serologic markers of hepatitis B virus, in order to assess the intrafamiliar spread of HBV infection. 40 relatives of 15 children affected by chronic hepatitis B (Group I) and 23 relatives of 14 patients affected by hemophilia (Group II) were studied. HBV markers (HBsAg, anti-HBs, anti-HBc, HBeAg, anti-HBe) were tested in all the subjects by RIA. Positive markers were found in 39 (62%) of the subjects; the combined prevalence for all HBV markers was 75% in the Group I, and 39% in the Group II. The higher prevalence rate in Group I can be explained by the possible previous infection of another member of the family, whereas in Group II the child is almost surely the first infected subject. Besides, subjects of Group I have probably been in contact with HBV infected children a longer time, compared to subjects in Group II. Our data suggest that household contacts of children with HBV infection are at high risk and should therefore be immunized against HBV.

[Evaluation of the nutritional status and growth of children with chronic HBsAg-positive hepatitis]. / Valutazione dello stato nutrizionale e dell'accrescimento in bambini con epatite cronica HBsAg positiva.

Chronic hepatitis in children seems to have a better prognosis than in adults, with a discrete trend to spontaneous remission. Actually biopsy and liver enzymes are mandatory for a correct follow up of the disease, while few authors are interested in the assessment of growth and nutritional status. We think that an auxological approach is one of the main points in every chronic disease of the pediatric age, chiefly when some anabolic step might be affected. Our first result in a cross sectional study of growth and nutritional status in a selected group of untreated HBsAg+ chronic hepatitis children are as follows. According to enzyme values in the range of 16-171 UI/1 SGOT all patients are growing very well with a good-discrete nutritional status. Though anthropometric proteic nutritional status (muscle circumference) was in the range of normal distribution, we were able to show a moderate correlation between SGOT and muscle circumference (r = -0,50). Our impression is that some patients with a worse hepatic damage can be exposed at risk of proteic malnutrition which is a negative element in the prognosis of every chronic disease. Anthropometric auxology can detect degrees of proteic malnutrition, and can follow its development. So we recommend routine auxological assessment in all pediatric patients with chronic hepatitis.

[Biliary atresia: pathogenetic considerations emerging from the histopathologic analysis of the liver parenchyma]. / L'atresia biliare: considerazioni patogenetiche emergenti dall'analisi istopatologica del parenchima epatico.

Nine patients had been surgically treated for extrahepatic biliary atresia from 1974 to 1982. The analysis of the hepatic specimens obtained during the surgical exploration revealed a wide spectrum of histopathologic lesions. In 3 patients we found severe Giant-cell transformation, while in the other 6 it was not possible to ascribe the histopathologic picture to a univocal pathogenesis. Comparing our results to the reports of other Authors we believe biliary atresia can not be explained by a single pathologic mechanism. The obstruction of the extrahepatic bile ducts might be the common morphologic denominator of different pathologic entities, from each of them it depends a different evolution of the hepatic lesions and a different survival after Kasai's operation.