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Towards sustainable sanitation management: Establishing the costs and willingness to pay for emptying and transporting sludge in rural districts with high rates of access to latrines.

PLoS One; 12(3): e0171735, 2017.
Article in English | MEDLINE | ID: mdl-28323885


MOTIVATION: Proper management of fecal sludge has significant positive health and environmental externalities. Most research on managing onsite sanitation so far either simulates the costs of, or the welfare effects from, managing sludge in situ in pit latrines. Thus, designing management strategies for onsite rural sanitation is challenging, because the actual costs of transporting sludge for treatment, and sources for financing these transport costs, are not well understood. METHODS: In this paper we calculate the actual cost of sludge management from onsite latrines, and identify the contributions that latrine owners are willing to make to finance the costs. A spreadsheet-based model is used to identify a cost-effective transport option, and to calculate the cost per household. Then a double-bound contingent valuation method is used to elicit from pit-latrine owners their willingness-to-pay to have sludge transported away. This methodology is employed for the case of a rural subdistrict in Bangladesh called Bhaluka, a unit of administration at which sludge management services are being piloted by the Government of Bangladesh. RESULTS: The typical sludge accumulation rate in Bhaluka is calculated at 0.11 liters/person/day and a typical latrine will need to be emptied approximately once every 3 to 4 years. The costs of emptying and transport are high; approximately USD 13 per emptying event (circa 14% of average monthly income); household contributions could cover around 47% of this cost. However, if costs were spread over time, the service would cost USD 4 per year per household, or USD 0.31 per month per household-comparable to current expenditures of rural households on telecommunications. CONCLUSION: This is one of few research papers that brings the costs of waste management together with financing of that cost, to provide evidence for an implementable solution. This framework can be used to identify cost effective sludge management options and private contributions towards that cost in other (context-specific) administrative areas where onsite sanitation is widespread.

Food safety knowledge, attitudes and practices of institutional food-handlers in Ghana.

BMC Public Health; 17(1): 40, 2017 Jan 06.
Article in English | MEDLINE | ID: mdl-28061850


BACKGROUND: In large scale cooking, food is handled by many individuals, thereby increasing the chances of food contamination due to improper handling. Deliberate or accidental contamination of food during large scale production might endanger the health of consumers, and have very expensive repercussions on a country. The purpose of this study was to evaluate the food safety knowledge, attitudes, and practices among institutional food- handlers in Ghana. METHODS: The study was conducted using a descriptive, cross-sectional survey of 29 institutions by conducting face to face interview and administration of questionnaire to two hundred and thirty-five (235) institutional food-handlers. The questionnaire was peer-reviewed and pilot tested in three institutions in the Upper East Region of Ghana, before the final version was distributed to food-handlers. The questionnaire was structured into five distinctive parts to collect information on (i) demographic characteristics, (ii) employees' work satisfaction, (iii) knowledge on food safety, (iv) attitudes towards food safety and (v) food hygiene practices. RESULTS: Majority of the food-handlers were between 41-50 years (39.1%). Female respondents were (76.6%). In our study, the food-handlers were knowledgeable about hygienic practices, cleaning and sanitation procedures. Almost all of the food-handlers were aware of the critical role of general sanitary practices in the work place, such as hand washing (98.7% correct answers), using gloves (77.9%), proper cleaning of the instruments/utensils (86.4%) and detergent use (72.8%). On disease transmission, the results indicates that 76.2% of the food- handlers did not know that Salmonella is a food borne pathogens and 70.6% did not know that hepatitis A is a food borne pathogen. However, 81.7% handlers agreed that typhoid fever is transmitted by food and 87.7% agreed that bloody diarrhea is transmitted by food. Logistic regression analysis testing four models showed statistically significant differences (p < 0.05), for models in which the explanatory variable was the level of education. CONCLUSIONS: In generally, the institutional food-handlers have satisfactory knowledge in food safety but this does not translate into strict hygienic practices during processing and handling food products.

Efficiency of sewage sludge biochar in improving urban soil properties and promoting grass growth.

Chemosphere; 173: 551-556, 2017 Apr.
Article in English | MEDLINE | ID: mdl-28142113


It is meaningful to quickly improve poor urban soil fertility in order to establish the green land vegetation. In this study, a series rates (0%, 1%, 5%, 10%, 20% and 50%, in mass ratio) of biochar derived from municipal sewage sludge was applied into an urban soil and then turf grass was grown in pots. The results showed that biochar amendment induced significant increases in soil total nitrogen, organic carbon, black carbon, and available phosphorus and potassium by more than 1.5, 1.9, 4.5, 5.6 and 0.4 times, respectively. Turf grass dry matter increased proportionally with increasing amount of added biochar (by an average of 74%), due to the improvement in plant mineral nutrition. Biochar amendment largely increased the total amounts of soil heavy metals. However, 43-97% of the heavy metals in the amended soil were concentrated in the residual fraction with low bioavailability. So the accumulation of heavy metals in turf grass aboveground biomass was highly reduced by the addition of biochar. These results indicated that sewage sludge biochar could be recommended in the poor urban raw soil as a soil conditioner at a rate of 50%. However, the environmental risk of heavy metal accumulation in soil amended with sewage sludge biochar should be carefully considered.

Monitoring sanitation and hygiene in the 2030 Agenda for Sustainable Development: A review through the lens of human rights.

Sci Total Environ; 580: 1108-1119, 2017 Feb 15.
Article in English | MEDLINE | ID: mdl-27989472


International monitoring of drinking water and sanitation has been jointly carried out by WHO and UNICEF through their Joint Monitoring Programme (JMP). With the end of the Millennium Development Goals (MDGs) era in 2015, the JMP has proposed a post-2015 framework for integrated monitoring of water and sanitation targets included in the Sustainable Development Goal no. 6. This article discusses how each element of the proposed sanitation target and corresponding indicators can be understood from a human rights perspective. Building on the MDGs, and although some of the weaknesses and gaps persist, the discussion suggests that the post-2015 proposal is a step forward towards a monitoring framework where human rights elements related to sanitation are effectively promoted. In addition, to support the interpretation and implementation of the normative content of human rights obligations related to sanitation, the study proposes a reduced set of easy-to-assess indicators to measure the normative criteria of this right, which are then grouped in a multidimensional framework to describe increasing levels of sanitation service. To do this, the study combines literature review and specific local experience from three case studies. It is shown that the proposed monitoring tools, namely the indicators and the multidimensional indicator framework, provide guidance on monitoring the human right to sanitation. In doing so, they might ultimately help sector stakeholders in the realization of this right.

Non-destructive soil amendment application techniques on heavy metal-contaminated grassland: Success and long-term immobilising efficiency.

J Environ Manage; 186(Pt 2): 167-174, 2017 Jan 15.
Article in English | MEDLINE | ID: mdl-27594691


Extensive contamination of grassland with cadmium (Cd), lead (Pb) and zinc (Zn) is a typical problem close to Pb/Zn smelter sites. The entry of Cd or Pb into the food chain is very likely, as are toxicity effects of Zn in plants. Previous promising results from pot and field experiments showed the high potential of using amendments for immobilisation to reduce metal input into the food chain via crops grown on smelter-contaminated soils at Arnoldstein (Austria) (Friesl et al., 2006). The aim of this study was to find a practical solution for large-scale contaminations in hilly regions that avoids erosion. Field application of amendments without destroying the vegetation cover (grassland) involved two approaches: (a) slurrying (Slu) the amendments into cut gaps in the vegetation cover and (b) injecting (Inj) the amendments through the vegetation cover. Here, we investigate the immobilising and long-term efficiency of treatments [gravel sludge (2.5%) + red mud (0.5%) (GS + RM)]. Risk assessment was based on soil, plant and water samples taken over a period of 10 years. Ammonium-nitrate-extractable Cd was reduced up to 50%, Pb up to 90%, and Zn over 90%. Plant uptake into the grass mixture and narrow leaf plantain was significantly reduced for Cd, Pb, and Zn. Harvesting early in vegetation period can further reduce uptake and meet the threshold for fodder crops. The reduction of these elements in the seepage water in 24 samplings within these 10 years reached 40%, 45% and 50%, respectively. Immobilisation increased microbial biomass and decreased human bioaccessibility for Pb. Our investigation of the long-term efficiency of GS + RM in all treatments shows that the Slu and Inj amendment application techniques have promising potential as a realistic and practical method for extensively contaminated hilly land. Slurrying performed best. We conclude that grassland remediation methods involving tillage are counterproductive from the viewpoint of bioaccessibility and soil protection and therefore should be avoided.

Three-step effluent chlorination increases disinfection efficiency and reduces DBP formation and toxicity.

Chemosphere; 2016 Dec 02.
Article in English | MEDLINE | ID: mdl-27919529


Chlorination is extensively applied for disinfecting sewage effluents, but it unintentionally generates disinfection byproducts (DBPs). Using seawater for toilet flushing introduces a high level of bromide into domestic sewage. Chlorination of sewage effluent rich in bromide causes the formation of brominated DBPs. The objectives of achieving a disinfection goal, reducing disinfectant consumption and operational costs, as well as diminishing adverse effects to aquatic organisms in receiving water body remain a challenge in sewage treatment. In this study, we have demonstrated that, with the same total chlorine dosage, a three-step chlorination (dosing chlorine by splitting it into three equal portions with a 5-min time interval for each portion) was significantly more efficient in disinfecting a primary saline sewage effluent than a one-step chlorination (dosing chlorine at one time). Compared to one-step chlorination, three-step chlorination enhanced the disinfection efficiency by up to 0.73-log reduction of Escherichia coli. The overall DBP formation resulting from one-step and three-step chlorination was quantified by total organic halogen measurement. Compared to one-step chlorination, the DBP formation in three-step chlorination was decreased by up to 23.4%. The comparative toxicity of one-step and three-step chlorination was evaluated in terms of the development of embryo-larva of a marine polychaete Platynereis dumerilii. The results revealed that the primary sewage effluent with three-step chlorination was less toxic than that with one-step chlorination, indicating that three-step chlorination could reduce the potential adverse effects of disinfected sewage effluents to aquatic organisms in the receiving marine water.

Flugzeugdesinfektion : Geeignete Desinfektionsmittel und Standardverfahren bei hochansteckenden Krankheiten. / Disinfection of aircraft : Appropriate disinfectants and standard operating procedures for highly infectious diseases.

Article in English | MEDLINE | ID: mdl-27785522


For infectious diseases caused by highly pathogenic agents (e. g., Ebola/Lassa fever virus, SARS-/MERS-CoV, pandemic influenza virus) which have the potential to spread over several continents within only a few days, international Health Protection Authorities have taken appropriate measures to limit the consequences of a possible spread. A crucial point in this context is the disinfection of an aircraft that had a passenger on board who is suspected of being infected with one of the mentioned diseases. Although, basic advice on hygiene and sanitation on board an aircraft is given by the World Health Organization, these guidelines lack details on available and effective substances as well as standardized operating procedures (SOP). The purpose of this paper is to give guidance on the choice of substances that were tested by a laboratory of Lufthansa Technik and found compatible with aircraft components, as well as to describe procedures which ensure a safe and efficient disinfection of civil aircrafts. This guidance and the additional SOPs are made public and are available as mentioned in this paper.

Efficiency of a cleaning protocol for the removal of enterotoxigenic Staphylococcus aureus strains in dairy plants.

Int J Food Microbiol; 238: 295-301, 2016 Dec 05.
Article in English | MEDLINE | ID: mdl-27716472


Staphylococci are considered a major concern in dairy plants mainly due to the intensive production flow, automation of processing plants and increased demand in the microbiological quality of dairy products. This study aimed to identify S. aureus strains isolated from three Brazilian dairy plants, evaluate the influence of time, temperature and contact surface on the bacterial adhesion process, as well as the efficiency of simulated hygiene and sanitation protocol in removing adhered cells. For genotypic analyses, the presence of icaA and icaD in strains was evaluated. Adherence assays were performed in biofilm reactor, comparing the influence of 2 temperatures (5°C and 35°C), 2 surfaces (stainless steel and polypropylene) and 4 contact times (3, 6, 12h and post-sanitization). To evaluate the process effectiveness in removing adhered cells, neutral detergent and sanitizing agent based on sodium hypochlorite were used in order to simulate the situation observed in one of the dairy plants analyzed. The presence of icaA and icaD genes was determined in 75.3% and 77.6% of strains, respectively; 70.6% of isolates showed both genes, whereas 17.6% showed no genes. Genes for enterotoxin production were found in all samples, relating to SEG and SEH toxins. The number of cells adhered on both surfaces was about 3 and 6 log CFU/cm at temperatures of 5°C and 35°C, respectively, for most situations evaluated, with significant increase over the evaluation period. In general, the temperature of 35°C favored greater adherence of S. aureus. At 5°C, there was a considerable number of adhered cells, but in populations significantly lower than those observed at 35°C. The cleaning and sanitizing protocol was ineffective in removing adhered cells; better performance of sodium hypochlorite was observed at 5°C, which should be related to lower adherence observed at this temperature. Thus, the process was not able to reduce the number of S. aureus bacteria adhered on both surfaces to safe levels under the conditions evaluated.

Impact of health education intervention on food safety and hygiene of street vendors: A pilot study.

Med J Armed Forces India; 72(3): 265-9, 2016 Jul.
Article in English | MEDLINE | ID: mdl-27546967


BACKGROUND: Street foods are major source of food to millions of people. However, these are frequently associated with food-borne illnesses. It is imperative that street food vendors are educated to maintain hygiene and hence safety of food. With this background, a pilot study was undertaken to assess the impact of health education intervention on food safety and hygiene of street vendors. The aim of this study was to assess impact of health education intervention on food safety of street vendors. METHODS: It was a before and after study conducted in twenty street vendors of an urban area. Tool based on Bureau of Indian Standards (BIS) 2012 was prepared with scoring system to rate hygiene and sanitation of street vendors (score 0-156). Health education was given to all and scores of these vendors on same tool were reassessed after four weeks. RESULTS: Mean age of the study subjects was 35 ± 13.2 years. Highest score attained in BIS tool for food safety was 104 out of 156 (66.6%). No vendor was found to have achieved excellent score. Reasons for poor score were poor condition of vending cart, location, lack personal hygiene and incorrect and unsafe food handling practices. After intervention, it was observed that there was no significant improvement in overall score of vendors. However, scores in domains of personal habits, hygiene and food handling practices improved significantly after intervention (p < 0.05). CONCLUSION: The street vendors do not meet required standards given by BIS for food safety. Health education alone can only partly improve food safety practices of street vendors.

Can Sierra Leone maintain the equitable delivery of their Free Health Care Initiative? The case for more contextualised interventions: results of a cross-sectional survey.

BMC Health Serv Res; 16: 258, 2016 Jul 13.
Article in English | MEDLINE | ID: mdl-27412299


BACKGROUND: In 2010, the Ministry of Health and Sanitation in Sierra Leone launched their Free Health Care Initiative (FHCI) for pregnant and lactating mothers and children under-5. Despite an increase in the update of services, the inequitable distribution of health services and health facilities remain important factors underlying the poor performance of health systems to deliver effective services. This study identifies current gaps in service delivery across two rural locations served by the same District Health Management Team (DHMT). METHODS: We employed a cross-sectional household survey using a two-stage probability sampling method to obtain a sample of the population across two rural locations in Bonthe District: the riverine and the mainland. Overall, a total of 393 households across 121 villages were surveyed in the riverine and 397 households across 130 villages were sampled on the mainland. Maternal health, child health and sanitation indicators in Bonthe District were compared using Pearson Chi-Squared test with Yates' Continuity Correction across the two areas. RESULTS: Women across the two regions self-reported significantly different uptake of family planning services. Children on the mainland had significantly greater rates of health facility based deliveries; being born in the presence of a skilled birth attendant; completed immunisation schedules; and higher rates of being brought to the health centre within 24 h of developing a fever or a suspected acute respiratory infection. Households on the mainland also reported significantly greater use of treated water and unrestricted access to a latrine. CONCLUSIONS: If the government of Sierra Leone is going to deliver on their promise to free health care for pregnant women and their children, and do so in a way that reduces inequalities, greater attention must be paid to the existing service delivery gaps within each District. This is particularly relevant to health policy post-Ebola, as it highlights the need for more contextualised service delivery to ensure equitable access for women and children.

Microbiological Safety of Street Vended Foods in Jigjiga City, Eastern Ethiopia.

Ethiop J Health Sci; 26(2): 161-70, 2016 Mar.
Article in English | MEDLINE | ID: mdl-27222629


BACKGROUND: Food safety problems are particularly becoming an increasingly serious threat to public health in developing countries. This study was conducted to assess microbiological safety of street vended foods from May to November, 2014 in Jigjiga City. METHODS: A cross-sectional design was used to answer questions concerning the current status of food hygiene and sanitation practire of street food vending sites. Interview and observational assessments were used to collect socio-demographic data about street food venders. One hundred thirty-two samples of street foods were aseptically collected from four 'kebeles' of Jigjiga City. Both descriptive and analytical statistical methods were applied. RESULTS: The majority of the street food vendors were women, 120(90.9%), with the average age group of 23-49 years, (42.85%), and 99(66.7%) them were illiterate. The study revealed that 95(72%) of the food samples had pathogenic bacterial contaminations. Three different bacterial species were isolated: E. coli 68(51.5%), S. aureus 85(64.4%) and 26(19.7%) Salmonella species. The highest incidence of S. aureus 23/33(69%) was seen in 'Sambusa'; the highest incidence of E. coli 24/33(73.5%) was observed in 'Pasta', while the highest Salmonella incidence was observed in 'Ades'. CONCLUSION: This study revealed that there is a reasonable gap on food safety knowledge among street food venders. The microbial profile was also higher compared to standards set by the World Health Organization. Due attention should be given by the government to improve knowledge about food safety and the quality standard of street foods sold in the City.

The investigation of the sludge reduction efficiency and mechanisms in oxic-settling-anaerobic (OSA) process.

Water Sci Technol; 73(10): 2311-23, 2016.
Article in English | MEDLINE | ID: mdl-27191551


This paper aims to provide a full understanding of the sludge reduction mechanisms in the oxic-settling-anaerobic (OSA) process and presents an evaluation of the sludge reduction efficiencies and sludge characteristics in this process compared to the conventional activated sludge process. Fifty-eight percent reduction in observed yield in the OSA process was achieved compared to the control system at the end of the operational period with no deterioration of effluent quality. The settleability of sludge in the OSA process was also found to be better than that of the control system in terms of sludge volume index. In long-term operation, capillary suction time and specific resistance to filtration values confirmed that the OSA process showed good filterability characteristics. The results of batch experiments showed that higher endogenous respiration in the systems might lead to lower sludge production and that energy uncoupling had only a limited impact on sludge reduction.

The Knowledge Base for Achieving the Sustainable Development Goal Targets on Water Supply, Sanitation and Hygiene.

Int J Environ Res Public Health; 13(6)2016 May 27.
Article in English | MEDLINE | ID: mdl-27240389


Safe drinking water, sanitation, and hygiene (WASH) are fundamental to an improved standard of living. Globally, 91% of households used improved drinking water sources in 2015, while for improved sanitation it is 68%. Wealth disparities are stark, with rural populations, slum dwellers and marginalized groups lagging significantly behind. Service coverage is significantly lower when considering the new water and sanitation targets under the sustainable development goals (SDGs) which aspire to a higher standard of 'safely managed' water and sanitation. Lack of access to WASH can have an economic impact as much as 7% of Gross Domestic Product, not including the social and environmental consequences. Research points to significant health and socio-economic consequences of poor nutritional status, child growth and school performance caused by inadequate WASH. Groundwater over-extraction and pollution of surface water bodies have serious impacts on water resource availability and biodiversity, while climate change exacerbates the health risks of water insecurity. A significant literature documents the beneficial impacts of WASH interventions, and a growing number of impact evaluation studies assess how interventions are optimally financed, implemented and sustained. Many innovations in behavior change and service delivery offer potential for scaling up services to meet the SDGs.

Improving health in the Arctic region through safe and affordable access to household running water and sewer services: an Arctic Council initiative.

Int J Circumpolar Health; 75: 31149, 2016.
Article in English | MEDLINE | ID: mdl-27132632


Important health disparities have been documented among the peoples of the Arctic and subarctic, including those related to limited access to in-home improved drinking water and sanitation services. Although improving water, sanitation and hygiene (WASH) has been a focus of the United Nations for decades, the Arctic region has received little attention in this regard. A growing body of evidence highlights inequalities across the region for the availability of in-home drinking WASH services and for health indicators associated with these services. In this review, we highlight relevant data and describe an initiative through the Arctic Council's Sustainable Development Working Group to characterize the extent of WASH services in Arctic nations, the related health indicators and climate-related vulnerabilities to WASH services. With this as a baseline, efforts to build collaborations across the Arctic will be undertaken to promote innovations that can extend the benefits of water and sanitation services to all residents.

Nitrogen and carbon removal efficiency of a polyvinyl alcohol gel based moving bed biofilm reactor system.

Water Sci Technol; 73(7): 1511-9, 2016.
Article in English | MEDLINE | ID: mdl-27054722


In this study, the effectiveness of polyvinyl alcohol (PVA) gel beads in treating domestic wastewater was investigated: a moving bed biofilm reactor (MBBR) configuration (oxic-anoxic and oxic) with 10% filling fraction of biomass carriers was operated in a continuously fed regime at temperatures of 25, 20, 15 and 6 °C with hydraulic retention times (HRTs) of 32 h, 18 h, 12 h and 9 h, respectively. Influent loadings were in the range of 0.22-1.22 kg N m(-3) d(-1) (total nitrogen (TN)), 1.48-7.82 kg chemical oxygen demand (COD) m(-3) d(-1) (organic) and 0.12-0.89 kg NH4(+)-N m(-3)d(-1) (ammonia nitrogen). MBBR performance resulted in the maximum TN removal rate of 1.22 kg N m(-3) d(-1) when the temperature and HRT were 6 °C and 9 h, respectively. The carbon removal rate at this temperature and HRT was 6.82 kg COD m(-3) d(-1). Ammonium removal rates ranged from 0.13 to 0.75 kg NH4(+)-N m(-3) d(-1) during the study. Total phosphorus and suspended solid removal efficiency ranged from 84 to 98% and 85 to 94% at an influent concentration of 3.3-7.1 mg/L and 74-356 mg/L, respectively. The sludge wasted from the MBBR exhibited light weight features characterized by sludge volume index value of 185 mL/g. Experimental data obtained can be useful in further developing the concept of PVA gel based wastewater treatment systems.

Microbiological Food Safety Status of Commercially Produced Tomatoes from Production to Marketing.

J Food Prot; 79(3): 392-406, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26939649


Tomatoes have been implicated in various microbial disease outbreaks and are considered a potential vehicle for foodborne pathogens. Traceback studies mostly implicate contamination during production and/or processing. The microbiological quality of commercially produced tomatoes was thus investigated from the farm to market, focusing on the impact of contaminated irrigation and washing water, facility sanitation, and personal hygiene. A total of 905 samples were collected from three largescale commercial farms from 2012 through 2014. The farms differed in water sources used (surface versus well) and production methods (open field versus tunnel). Levels of total coliforms and Escherichia coli and prevalence of E. coli O157:H7 and Salmonella Typhimurium were determined. Dominant coliforms were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. No pathogens or E. coli were detected on any of the tomatoes tested throughout the study despite the high levels of coliforms (4.2 to 6.2 log CFU/g) present on the tomatoes at the market. The dominant species associated with tomatoes belonged to the genera Enterobacter, Klebsiella, and Citrobacter. Water used on the farm for irrigation considered not fit for purpose according to national agricultural irrigation standards, with high E. coli levels resulting from either a highly contaminated source water (river water at 3.19 log most probable number [MPN]/100 ml) or improper storage of source water (stored well water at 1.72 log MPN/100 ml). Salmonella Typhimurium was detected on two occasions on a contact surface in the processing facility of the first farm in 2012. Contact surface coliform counts were 2.9 to 4.8 log CFU/cm(2). Risk areas identified in this study were water used for irrigation and poor sanitation practices in the processing facility. Implementation of effective food safety management systems in the fresh produce industry is of the utmost importance to ensure product safety for consumers.

Efficiency of wastewater treatment in SBR and IFAS-MBSBBR systems in specified technological conditions.

Water Sci Technol; 73(6): 1349-56, 2016.
Article in English | MEDLINE | ID: mdl-27003075


The objective of this study is to compare wastewater treatment effectiveness in sequencing batch reactor (SBR) and integrated fixed-film activated sludge-moving-bed sequencing batch biofilm reactor (IFAS-MBSBBR) systems in specific technological conditions. The comparison of these two technologies was based on the following assumptions, shared by both series, I and II: the reactor's active volume was 28 L; 8-hour cycle of reactor's work, with the same sequence and duration of its consecutive phases; and the dissolved oxygen concentration in the aerobic phases was maintained at a level of 3.0 mg O2/L. For both experimental series (I and II), comparable effectiveness of organic compound (chemical oxygen demand (COD)) removal, nitrification and biological phosphorus removal has been obtained at levels of 95.1%, 97% and 99%, respectively. The presence of the carrier improved the efficiency of total nitrogen removal from 86.3% to 91.7%. On the basis of monitoring tests, it has been found that the ratio of simultaneous denitrification in phases with aeration to the total efficiency of denitrification in the cycle was 1.5 times higher for IFAS-MBSBBR.

Assessment of microbial viability in municipal sludge following ultrasound and microwave pretreatments and resulting impacts on the efficiency of anaerobic sludge digestion.

Appl Microbiol Biotechnol; 100(6): 2855-68, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26590585


A range of ultrasonication (US) and microwave irradiation (MW) sludge pretreatments were compared to determine the extent of cellular destruction in micro-organisms within secondary sludge and how this cellular destruction translated to anaerobic digestion (AD). Cellular lysis/inactivation was measured using two microbial viability assays, (1) Syto 16® Green and Sytox® Orange counter-assay to discern the integrity of cellular membranes and (2) a fluorescein diacetate assay to understand relative enzymatic activity. A range of MW intensities (2.17-6.48 kJ/g total solids or TS, coinciding temperatures of 60-160 °C) were selected for comparison via viability assays; a range of corresponding US intensities (2.37-27.71 kJ/g TS, coinciding sonication times of 10-60 min at different amplitudes) were also compared to this MW range. The MW pretreatment of thickened waste activated sludge (tWAS) caused fourfold to fivefold greater cell death than non-pretreated and US-pretreated tWAS. The greatest microbial destruction occurred at MW intensities greater than 2.62 kJ/g TS of sludge, after which increased energy input via MW did not appear to cause greater microbial death. In addition, the optimal MW pretreatment (80 °C, 2.62 kJ/g TS) and corresponding US pretreatment (10 min, 60 % amplitude, 2.37 kJ/g TS) were administered to the tWAS of a mixed sludge and fed to anaerobic digesters over sludge retention times (SRTs) of 20, 14, and 7 days to compare effects of feed pretreatment on AD efficiency. The digester utilizing MW-pretreated tWAS (80 °C, 2.62 kJ/g TS) had the greatest fecal coliform removal (73.4 and 69.8 % reduction, respectively), greatest solids removal (44.2 % TS reduction), and highest overall methane production (248.2 L CH4/kg volatile solids) at 14- and 7-day SRTs. However, despite the fourfold to fivefold increases in cell death upon pretreatment, improvements from the digester fed MW-pretreated sludge were marginal (i.e., increases in efficiency of less than 3-10 %) and likely due to a smaller proportion of cells (10-20 %) in the polymeric network and mixed sludge fed to digesters.

Enhancing nitrogen removal efficiency and reducing nitrate liquor recirculation ratio by improving simultaneous nitrification and denitrification in integrated fixed-film activated sludge (IFAS) process.

Water Sci Technol; 73(4): 827-34, 2016.
Article in English | MEDLINE | ID: mdl-26901725


An integrated fixed-film activated sludge (IFAS) process (G1) and an activated sludge anoxic-oxic process (G2) were operated at nitrate liquor recirculation ratio (R) of 100, 200 and 300% to investigate the feasibility of enhancing nitrogen removal efficiency (RTN) and reducing R by improving simultaneous nitrification and denitrification (SND) in the IFAS process. The results showed that the effluent NH4(+)-N and total nitrogen (TN) of G1 at R of 200% were less than 1.5 and 14.5 mg/L, satisfying the Chinese discharge standard (NH4(+)-N < 5 mg/L; TN < 15 mg/L). However, the effluent NH4(+)-N and TN of G2 at R of 300% were higher than 8.5 and 15.3 mg/L. It indicated that better RTN could be achieved at a lower R in the IFAS process. The polymerase chain reaction-denaturing gradient gel electrophoresis results implied that nitrifiers and denitrifiers co-existed in one microbial community, facilitating the occurrence of SND in the aerobic reactor of G1, and the contribution of SND to TN removal efficiency ranged 15-19%, which was the main reason that the RTN was improved in the IFAS process. Therefore, the IFAS process was an effective method for improving RTN and reducing R. In practical application, this advantage of the IFAS process can decrease the electricity consumption for nitrate liquor recirculation flow, thereby saving operational costs.
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