Bioremediation of reverse osmosis concentrate generated from the treatment of landfill leachate.

The moisture content of municipal solid waste (MSW) and local precipitation events lead to the leachate generation from MSW landfills. The high concentration of organic pollutants in landfill leachate (LL) makes it hazardous, requiring treatment before disposal into the environment. LL is most commonly treated by reverse osmosis (RO), which generates large volumes of concentrate known as RO concentrate. This investigation aims to stabilize the RO concentrate through an inexpensive and effective bioremediation strategy. A bench-scale aerobic suspended growth reactor study was conducted using three commercial conversion agents, namely EM.1, Bokashi powder, and coir pith powder. Overall bench-scale efficiency of 63% was achieved in this study. The onsite studies were conducted in 7.5-m3 artificial ponds with 46% efficiency amid atmospheric influences and constraints. The overall efficiencies of both bench and field-scale studies were derived by ascertaining the arithmetic mean of the individual efficiency of the following parameters: chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total dissolved solids (TDS). In contrast, the control pond with no conversion agents showed an increase in pollution concentration over the 100 days of retention time. The findings revealed that the investigated technology had a marginally lower evaporation rate and performed relatively well compared to traditional solar evaporation ponds. Moreover, the technology can be easily scaled-up and readily applied for RO concentrate treatment in MSW landfills.

Contaminants of emerging concerns (CECs) in a municipal wastewater treatment plant in Indonesia.

This study provides the first set of quantitative data on the occurrence and fate of a wide range of contaminants of emerging concerns (CECs) in Indonesia's largest wastewater treatment plant (WWTP). The WWTP employs waste stabilization ponds (WSPs) as the secondary treatment before discharging the effluent to the Citarum River. Fourteen out of twenty-two monitored CECs were detected in the wastewater influent, and seven were present in the effluent, with a total concentration of 29.8 ± 0.4 µg/L and 0.5 ± 0.0 µg/L, respectively. The occurrence of the CECs in this study was found to be well correlated with their possible use and known detection in surface waters in Indonesia. Caffeine (CAF) at 12.2 ± 0.1 µg/L, acetaminophen (ACT) at 9.1 ± 0.1 µg/L, N,N-diethyl-m-toluamide (DEET) at 5.0 ± 0.1 µg/L, ibuprofen (IBU) at 2.3 ± 0.0 µg/L, and triclosan (TCS) at 470 ± 64 ng/L were discovered as the five most prevalent CECs, followed by bisphenol A (BPA), trimethoprim (TMP), Tris(2-chloroethyl) phosphate (TCEP), sulfamethazine (SMZ), carbamazepine (CBZ), fluoxetine (FLX), benzotriazole (BTA), sulfamethoxazole (SMX), and metformin (METF). Biodegradable CECs (SMX, SMZ, ACT, IBU, TCS, BPA, CAF, DEET, and TMP) were efficiently removed (83-100%) by the WSP. In contrast, recalcitrant CECs achieved poor removal efficiencies (e.g., FLX at 24%), and for others, treatment processes even resulted in elevated concentrations in the effluent (CBZ by 85%, TCEP by 149%, and BTA by 92%). The CECs' influent concentrations were determined to pose a moderate aquatic cumulative risk, while no such risk was associated with their effluent concentrations. The study demonstrates the importance of conventional WWTPs in reducing the concentrations of CECs to minimize their aquatic contamination risk. The findings are relevant for countries, such as Indonesia, with limited resources for advanced centralized wastewater treatments, and which are exploring the efficacy of centralized WSP against the existing decentralized treatments.

Waste Stabilization Pond (WSP) for wastewater treatment: A review on factors, modelling and cost analysis.

Waste stabilization pond (WSP) is natural technology which can be installed in centralized or semi-centralized sewerage systems for treatment of domestic and industrial wastewater, septage and sludge, etc. WSPs are highly efficient, simple to construct, low cost and easy to operate. It can be used as secondary or tertiary treatment unit in a treatment plant either individually or in a coupling manner. The algal-bacterial symbiosis in WSP makes it completely natural treatment process for which it becomes economic as compared to other treatment technologies in terms of its maintenance cost and energy requirement. Effluent from WSP can also be used for agricultural purpose, gardening, watering road, vehicle wash, etc. Advance technologies are being integrated for better design and efficiency of WSP, but the main challenges are the separation and removal of algal species which lead to deterioration of the water if stays long. Research is necessary to maximize algal growth yield, selection of beneficial strain and optimizing harvesting methods. This review focuses on the treatment mechanism in the pond, affecting factors, types of ponds, design equation, cost analysis.

Performance evaluation and siting index of the stabilization ponds based on environmental parameters: a case study in Iran.

Stabilization ponds are open pools that remove total suspended solids, organic matters, microbial and pathogenic agents using physical, chemical, and biological processes. If the stabilization ponds are not well designed, they can produce odors, breed many insects, increase suspended solids concentration in the effluent and pollute groundwater. Consideration of environmental factors is critical for operation and maintenance. In this study, first, information on wastewater treatment plants and meteorological parameters were collected, and simultaneously, specialists were selected to score the effect of environmental factors on stabilization pond efficiency. A geographic information system was used to sit for suitable locations for stabilization ponds. The results showed that 23.6 % of Iran's treatment plants are stabilization ponds, which based on climate, evaporation, sunny hours, ice days, wind speed, and temperature parameters, 33.33 %, 37.3 %, 14 %, 50 %, 64 and 26 % of the stabilization ponds have obtained good points, respectively. The results also showed that 50 % of the stabilization ponds obtained an acceptable score considering all environmental parameters' simultaneous effect. A preliminary study based on considering all the environmental parameters showed that the central and southern regions are the best areas for establishing waste stabilization ponds; in contrast, northern and northeastern regions can have high operation and maintenance costs with lower efficiency. This study has shown that setup and design of the new waste stabilization ponds in Iran need to take into account by considering environmental factors because these factors have the main effect on algae growth which are one of main biological treatment.

Comparison of advanced biological treatment and nature-based solutions for the treatment of pharmaceutically active compounds (PhACs): A comprehensive study for wastewater and sewage sludge.

Passing of pharmaceutical residues into environment in an uncontrolled manner as a result of continuous increase in drug consumption across the globe has become a threatening problem for the ecosystems and almost all living creatures. In this study, diclofenac (DCF), carbamazepine (CBZ), 17ß-estradiol (17ß-E2) and 17α-ethynylestradiol (EE2) belonging to different therapeutic classes were investigated simultaneously in advanced biological treatment and nature-based treatments during 12-months sampling campaign. In this context, behavior patterns of pharmaceutically active compounds (PhACs) throughout the both wastewater and sludge lines in advanced biological wastewater treatment plant (WWTP), wastewater stabilization pond (WSP) and constructed wetland (CW) were discussed in detail based on each treatment processes seasonally. Furthermore, statistically evaluated data obtained in full-scale WWTPs were compared with each other in order to determine the valid removal mechanisms of these pharmaceutical compounds. While DCF and CBZ were detected very intensively both in the wastewater and sludge lines of the investigated WWTPs, steroid hormones,17ß-E2 and EE2, were determined below the LOQ value in general. Annual average removal efficiencies achieved in studied WWTPs for DCF ranged between -23.3% (in CW) and 75.2% (in WSP), while annual average removal rates obtained for CBZ varied between -20.7% (in advanced biological treatment) and 10.0% (in CW). It has been found that DCF was highly affected by different wastewater treatment processes applied in the WWTPs compared to CBZ which showed extraordinary resistance to all different treatment processes. Although calculated in different rates for each compounds, biodegradation/biotransformation and sorption onto sewage sludge were determined as the main removal mechanisms for PhACs in plants. Although showed a similar behavior in the sludge dewatering unit (decanter) present in the advanced biological WWTP, quite different behaviors observed in the anaerobic digester for DCF (up to 15% decrease) and CBZ (up to 95% increase). Sorption and desorption behaviors of DCF and CBZ were also evaluated in the sludge treatment processes found in advanced biological WWTP. Percentages of originated extra annual average of pharmaceutical loads were calculated as 0.64% and 0.90% for DCF and CBZ, respectively in the advanced biological WWTP due to the sidestream caused by the sludge dewatering unit.

Spatial and temporal variations of greenhouse gas emissions from a waste stabilization pond: Effects of sludge distribution and accumulation.

Due to regular influx of organic matter and nutrients, waste stabilization ponds (WSPs) can release considerable quantities of greenhouse gases (GHGs). To investigate the spatiotemporal variations of GHG emissions from WSPs with a focus on the effects of sludge accumulation and distribution, we conducted a bathymetry survey and two sampling campaigns in Ucubamba WSP (Cuenca, Ecuador). The results indicated that spatial variation of GHG emissions was strongly dependent on sludge distribution. Thick sludge layers in aerated ponds and facultative ponds caused substantial CO2 and CH4 emissions which accounted for 21.3% and 78.7% of the total emissions from the plant. Conversely, the prevalence of anoxic conditions stimulated the N2O consumption via complete denitrification leading to a net uptake from the atmosphere, i.e. up to 1.4±0.2 mg-N m-2 d-1. Double emission rates of CO2 were found in the facultative and maturation ponds during the day compared to night-time emissions, indicating the important role of algal respiration, while no diel variation of the CH4 and N2O emissions was found. Despite the uptake of N2O, the total GHG emissions of the WSP was higher than constructed wetlands and conventional centralized wastewater treatment facilities. Hence, it is recommended that sludge management with proper desludging regulation should be included as an important mitigation measure to reduce the carbon footprint of pond treatment facilities.

Occurrence, loadings and removal of EU-priority polycyclic aromatic hydrocarbons (PAHs) in wastewater and sludge by advanced biological treatment, stabilization pond and constructed wetland.

Eight polycyclic aromatic hydrocarbon (PAH) compounds which have been accepted as priority micropollutants by European Union (EU) were analyzed both in wastewater and sludge lines throughout three full scale (located in city, sub-province and village) WWTPs during 12-month sampling period. Investigated WWTPs have different treatment types including advanced biological treatment, stabilization pond (SP) and constructed wetland (CW). Removal efficiencies for total PAH compounds varied from 48% in CW to 85% in advanced biological treatment plant. The maximum concentrations of 360-2282 ng/L observed for naphthalene in raw wastewater were decreased to 103-370 ng/L by treatment processes. Minimum concentration were detected for benzo(k)fluoranthene (B[k]F) and benzo(g,h,i)perylene (B[g,h,i]P) ranged between 8 and 12 ng/L and 19-33 ng/L, respectively. While minimum removal efficiencies were obtained for B[k]F and B[g,h,i]P maximum removal efficiencies were obtained for naphthalene in all WWTPs. PAHs present in minimum and maximum levels in the sludge samples were detected as 54 and 6826 ng/g for the B[g,h,I]P and naphthalene, respectively. Considering the removal mechanisms, PAHs have been determined to be removed by biodegradation or vaporization up to 84% and by settling (adsorption onto sludge) up to 2%. The greatest portion (99%) of naphthalene and anthracene were determined to be biodegraded or vaporized in biological treatment due to their low molecular weights. On the other hand, mechanism of adsorption onto sludge was determined as negligible for these two compounds. In addition, approximately 14% of PAHs were discharged to the receiving environment. Among the different WWTP types investigated, advanced biological treatment was found to be the most efficient plant for the removal of PAH compounds.

Acinetobacter baumannii detected on modified charcoal-cefoperazone-deoxycholate agar in a waste stabilization pond.

Campylobacter is a recommended reference pathogen for the verification and validation of water recycling schemes in Australia and globally. In a larger study investigating the efficacy of pathogen removal in waste stabilization ponds (WSP), we cultivated bacteria from wastewater samples on modified charcoal-cefoperazone-deoxycholate agar (mCCDA) targeting the growth of Campylobacter. A high number of colonies characteristic of Campylobacter grew on this selective medium, but this did not correlate with qPCR data. Using primers targeting the 16S rRNA gene, and additional confirmatory tests to detect VS1, ompA, blaOXA-51-like, blaOXA-23-like genes, we tested 80 random colonies from 10 WSP samples. All 80 were identified as Acinetobacter baumannii. Wastewater grab samples taken three times over 6 months throughout the WSP system showed removal of A. baumannii in the WSP at rates similar to that of Escherichia coli. Our study suggests that mCCDA agar is not a suitable medium for isolating Campylobacter from environmental samples and that A. baumannii can be used as an indicator for removal of pathogens in WSPs.

Decay rates of Escherichia coli, Enterococcus spp., F-specific bacteriophage MS2, somatic coliphage and human adenovirus in facultative pond sludge.

The purpose of this study was to evaluate the efficacy of a waste stabilization pond (WSP) system to reduce pathogen contaminants in sludge. This included examining the factors that influence the fate and concentration of human pathogens and their indicators in two sludge layers. The decay rates of five study microorganisms were determined under in-situ conditions at a WSP. The background levels of fecal origin microorganisms were consistently detected (ranging: Escherichia coli 104 to 106, enterococci 101 to 103, F-specific bacteriophage (MS2) 101 to 103 and somatic coliphage 101 to 104 colony-forming units (CFU) mL-1, as well as 101 to 102 human adenovirus gene copies mL-1) in the primary facultative pond. Among microorganisms tested, the bacteria generally decayed faster than adenovirus and bacteriophage, particularly in the upper sludge layer. Due to the observed regrowth of E. coli, it may have a limited value as an indicator for pathogen removal in the wastewater stabilization ponds. The abundance of E. coli numbers within the pond biome followed changes in pond temperature over time. The results of the study suggest that viruses could survive for a long time, particularly in deeper layers (>1 metre) in the sludge, during winter months (T90 = 156 d). The presence of human pathogens in WSP sludge, in particular viruses, may be a barrier to its beneficial reuse in agriculture. The results indicate that additional treatment of sludge may be required to mitigate potential public health risks from reuse of sludge for agricultural purposes.

Wastewater discharge with phytoplankton may favor cyanobacterial development in the main drinking water supply river in Uruguay.

The main drinking water source supplying Uruguay (Santa Lucía River, SLR) was threatened in 2013 by a cyanobacterial bloom transported downstream to the water treatment plant that provides water to half of this country population. Several eutrophic reservoirs and stabilization ponds located in the river basin may have been the source of cyanobacterial populations. Such conditions may be common in productive basins; however, few studies have evaluated the impact of microalgae from wastewater stabilization ponds on rivers and its viability downstream. The effect of a dairy wastewater effluent on SLR was studied by means of nutrient and chlorophyll a loads, phytoplankton composition, and effluent incubation in river water in order to evaluate the potential development of cyanobacteria. Total phosphorus and nitrogen loads of the effluent reached up to 25% and 17% of SLR, respectively, while chlorophyll a was up to 37%. The upstream-downstream evaluation showed an increase in dissolved phosphorus and chlorophyll a. The effluent phytoplankton (14.16 mm3 L-1) was dominated by organisms < 10 µm and diatoms (91%), and 3% of cyanobacteria. Cyanobacteria were not detected in SLR, though it appeared downstream of the effluent discharge. At the end of the bioassay, cyanobacterial biomass became the dominant group (37%). This study shows the potential development of cyanobacteria present in industrial effluents when diluted in river water. The effect of phytoplankton discharge from stabilization ponds is not generally considered in monitoring assessments and environment management, despite representing a particular risk if the water body is used as a drinking water source.

Identification of microalgae from waste stabilization ponds and evaluation of electroflotation by alternate current for simultaneous biomass separation and cell disruption / Identificação de microalgas de lagoas de estabilização e avaliação do método de eletroflotação por corrente alternada para separação e ruptura celular simultâneas

ABSTRACT This work aimed to investigate algal diversity at the genus level in stabilization pond systems treating domestic wastewater and to evaluate the feasibility of an electroflotation by alternate current (EFAC) system for simultaneous microalgae separation and cell disruption. Evaluation of algal diversity showed that the genera Euglena and Chlorella were present in relatively high frequencies in five of the six effluents analyzed. The use of EFAC on an effluent that presented bloom of Chlorella achieved turbidity and chlorophyll-a removal efficiencies higher than 70 and 90%, respectively, after 70 minutes of operation. Total lipid yield for the Chlorella-rich biomass was 21.4±2.02%. Such high biomass lipid content demonstrates the potential for obtaining lipid-based biofuels from wastes. The current paper describes the first attempt, with promising results, at using electroflotation by alternate current for low cost, simultaneous microalgae harvesting and disruption.

RESUMO Este trabalho objetivou investigar a diversidade algal no que se refere a gênero em sistemas de lagoas de estabilização tratando esgoto doméstico, bem como analisar a viabilidade de um sistema de eletroflotação por corrente alternada para obter simultaneamente separação e ruptura celular. A avaliação de diversidade algal mostrou que os gêneros Euglena e Chlorella estiveram presentes com relativamente elevada frequência em cinco dos seis efluentes analisados. A aplicação de eletroflotação por corrente alternada em um efluente que apresentou elevada predominância de Chlorella alcançou eficiências de remoção de turbidez e clorofila-a maiores que 70 e 90%, respectivamente, depois de 70 minutos de operação. O rendimento de lipídios totais para a biomassa rica em Chlorella foi de 21,4±2,02%. Esse elevado teor lipídico demonstra potencial para obtenção de biodiesel de lipídios de efluentes. O presente artigo descreve uma primeira tentativa, com resultados promissores, da utilização de eletroflotação por corrente alternada para separação e ruptura celular simultânea com baixo custo.

Comparison of biological weighting functions used to model endogenous sunlight inactivation rates of MS2 coliphage.

Sunlight inactivation is important for disinfection of viruses in sunlit waters. As such, attempts have been made to predict the endogenous photoinactivation rate of bacteriophage MS2 using biological weighting functions, which describe microorganism sensitivity to sunlight inactivation as a function of wavelength. In this study, four biological weighting function models were compared to assess their ability to predict endogenous inactivation rates (kendo) of MS2. Previously-published and newly-collected datasets consisting of an incident irradiance spectrum (used as an input to the model) and a measured inactivation rate (kobs) were used for model validation and comparison. kendo values predicted by each model were compared with measured kobs to evaluate the ability of each biological weighting function to predict endogenous sunlight inactivation rates. A model previously developed by Mattle et al. (Env. Sci. Technol. 49, 334-342) over-predicted inactivation rates, whereas the other three models - a model from Fisher et al. (Env. Sci. Technol. 45, 9249-9255), a new model developed in this study, and a modification of the model by Mattle et al. (developed as part of this study) - were better able to estimate inactivation rates. The biological relevance of the spectral shape of each biological weighting function is discussed.

Evaluation of hydraulic performance of an anaerobic pond using radiotracer technique.

A radiotracer investigation was carried out in a wastewater stabilization pond using radiotracer technique. Residence time distribution (RTD) of wastewater was measured using Iodine-131 as a radiotracer. The measured RTD was treated and mean residence time (MRT) was determined. The measured MRT was compared with the theoretical MRT and dead volume was estimated. It was found that about 93% of the geometric volume within the anaerobic pond was dead. The measured RTD was modeled using various RTD models and eventually a suitable model was identified to describe and visualize the flow pattern of wastewater within the pond. Based on the measured MRT, estimated dead volume and identified flow patterns, it was concluded that the hydraulic performance of the anaerobic pond was very poor and not suitable for its intended purpose.

An integrated mechanistic modeling of a facultative pond: Parameter estimation and uncertainty analysis.

Imitating natural lakes, pond treatment systems inherit a high complexity with interconnected web of biochemical reactions and complex hydraulic processes. As such, its simulation requires a large and integrated model, which has been a challenge for pond engineers. In this study, we develop an all-encompassing model to gain a quantitative and comprehensive understanding of the hydraulic, physicochemical and microbiological conversion processes in the most common pond, a facultative pond. Moreover, to deal with an evitable issue of large mechanistic models as overparameterization leading to poor identifiability, a systematic parameter estimation was implemented. The application of sensitivity analysis reveals the most influential parameters on pond performance. Particularly, physical parameters, such as vertical eddy diffusivity, water temperature, and maximum growth rate of heterotrophs induce the most changes of organic matters while microbial assimilation and ammonia volatilization appear to be main processes for nutrient removal. In contrast, the efficiency of phosphate precipitation and nutrient biological removal via polyphosphate accumulating organisms and denitrifying bacteria is limited. Identifiability problems are addressed mainly by the characterization of light dependence of algal growth, interaction between water temperature and its coefficient, and the growth of autotrophic bacteria while based on the determinant measures, the most important parameter subsets affecting model outputs are related to physical processes and algal activity. After the establishment of the influential and identifiable parameter subset, an automatic calibration with the data collected from Ucubamba pond system (Ecuador) demonstrates the effect of high-altitude climatic conditions on pond behaviors. An aerobic prevailing condition is observed as a result of high light intensity causing accelerated algal activities, hence, leading to the limitation of hydrolysis, anaerobic processes, and the growth of anoxic heterotrophs for denitrification. Furthermore, the output of uncertainty analysis indicates that a large avoidable uncertainty as a result of vast complexity of the applied model can be reduced greatly via a systematic approach for parameter estimation.

Occurrence, fate and removal of pharmaceuticals, personal care products and pesticides in wastewater stabilization ponds and receiving rivers in the Nzoia Basin, Kenya.

Although there is increased global environmental concern about emerging organic micropollutants (EOMPs) such as pharmaceuticals, personal care products (PPCPs) and polar pesticides, limited information is available on their occurrence in Africa. This study presents unique data on concentrations and loads of 31 PPCPs and 10 pesticides in four wastewater stabilization ponds (WSPs) and receiving rivers (flowing through urban centres) in Kenya. The WSPs indicate a high potential to remove pharmaceutically active compounds (PhACs) with removals by up to >4 orders of magnitude (>99.99% removal), mainly occurring at the facultative stage. However, there are large differences in removal among the different classes, and a shift in the relative PhACs occurrence is observed during wastewater treatment. Whereas the influent is dominated by high-consumption PhACs like anti-inflammatory drugs (e.g. paracetamol and ibuprofen, up to 1000 µg L-1), the most recalcitrant PhACs including mainly antibiotics (e.g. sulfadoxin and sulfamethoxazole) and antiretrovirals (e.g. lamivudine and nevirapine) are largely abundant (up to 100 µg L-1) in treated effluent. Overall, concentrations of EOMPs in the Nzoia Basin rivers are the highest in dry season (except pesticides) and in small tributaries. They are of the same order of magnitude as those measured in the western world, but clearly lower than what we recently measured in the Ngong River, Nairobi region. Based on the specific consumption patterns and recalcitrant behavior, high concentrations (>1000 ng L-1) are observed in the rivers for PPCPs like lamivudine, zidovudine, sulfamethoxazole and methylparaben. Concentration levels of pesticides are in general one order of magnitude lower (<250 ng L-1). Our data suggest a continuous input of EOMPs to the rivers from both point (WSPs) and diffuse (urban centres) sources. To better understand and manage the impact of both sources, EOMP removal mechanisms in WSPs and their attenuation in rivers merit further research.

Determining variables that influence the phosphorus content of waste stabilization pond algae.

Waste stabilization ponds (WSP) are one of the most common forms of wastewater treatment for smaller communities globally, but have poor phosphorus removal. It is known that WSP algae can accumulate polyphosphate within their cells in excess of that needed for cell function. If polyphosphate accumulation could be triggered at the higher range of WSP cell concentrations, phosphorus removal from domestic wastewater could be significantly improved. However, this phenomenon is sporadic and still not fully understood. With a view of building a fundamental understanding to underpin the engineering of a new phosphorus removal process, this paper examines eight previously untested variables that may influence the cellular phosphorus content of WSP biomass. Although calcium, magnesium, and potassium are key constituents of polyphosphate granules, the concentrations tested were not limiting to polyphosphate accumulation. While literature also pointed to inoculum characteristics as potentially having an impact, no significance was found in this research. Conversely, three important new triggers where identified that significantly (90% confidence) affected the cellular phosphorus content of WSP biomass. An increase in cellular phosphorus content was triggered by decreasing the organic load, or allowing the pH to increase as compared to pH control. By contrast, the presence of mixing decreased the phosphorus content of the WSP biomass.

Occurrence and risk assessment of antibiotics in water and lettuce in Ghana.

Hospital wastewater and effluents from waste stabilization ponds in Kumasi, Ghana, are directly discharged as low quality water into nearby streams which are eventually used to irrigate vegetables. The presence of 12 commonly used antibiotics in Ghana (metronidazole, ciprofloxacin, erythromycin, trimethoprim, ampicillin, cefuroxime, sulfamethoxazole, amoxicillin, tetracycline, oxytetracycline, chlortetracycline and doxycycline) were investigated in water and lettuce samples collected in three different areas in Kumasi, Ghana. The water samples were from hospital wastewater, wastewater stabilization ponds, rivers and irrigation water, while the lettuce samples were from vegetable farms and market vendors. Antibiotics in water samples were extracted using SPE while antibiotics in lettuce samples were extracted using accelerated solvent extraction followed by SPE. All extracted antibiotics samples were analyzed by HPLC-MS/MS. All studied compounds were detected in concentrations significantly higher (p=0.01) in hospital wastewater than in the other water sources. The highest concentration found in the present study was 15µg/L for ciprofloxacin in hospital wastewater. Irrigation water samples analyzed had concentrations of antibiotics up to 0.2µg/L. Wastewater stabilization ponds are low technology but effective means of removing antibiotics with removal efficiency up to 95% recorded in this study. However, some chemicals are still found in levels indicating medium to high risk of antibiotics resistance development in the environment. The total concentrations of antibiotics detected in edible lettuce tissues from vegetable farms and vegetable sellers at the markets were in the range of 12.0-104 and 11.0-41.4ng/kg (fresh weight) respectively. The antibiotics found with high concentrations in all the samples were sulfamethoxazole, erythromycin, ciprofloxacin, cefuroxime and trimethoprim. Furthermore, our study confirms the presence of seven antibiotics in lettuce from irrigation farms and markets, suggesting an indirect exposure of humans to antibiotics through vegetable consumption and drinking water in Ghana. However, estimated daily intake for a standard 60kg woman was 0.3ng/day, indicating low risk for human health.

Predicting microalgae growth and phosphorus removal in cold region waste stabilization ponds using a stochastic modelling approach.

A stochastic ecological model with an integrated equilibrium temperature model was developed to predict microalgae growth and phosphorus removal in cold region waste stabilization ponds (WSPs). The model utilized a Monte Carlo simulation to account for parameter uncertainty. The equilibrium temperature model was parameterized using field data collected from two WSPs in Nunavut, Canada, from 2012 to 2014. The equilibrium temperature model provided good agreement with field data on a daily time step. The full model was run using historic (1956-2005) temperature and solar radiation data from five communities (Baker Lake, Cambridge Bay, Coral Harbour, Hall Beach, Resolute) in Nunavut, Canada. The communities represented a range of geographical locations and environmental conditions. Logistic regression on pooled model outputs showed that mean July temperature and mean treatment season temperature (June 1-September 15, ice-free period) provided the best predictors for microalgae growth. They had a predictive success rate of 93 and 88%, respectively. The modelled threshold (50% probability from the Monte Carlo simulation) for microalgae growth was 8.7 and 5.6 °C for the July temperature and mean treatment season temperature, respectively. The logistic regression was applied to each community (except Sanikiluaq) in Nunavut using historic climate data and a probability of microalgae growth was calculated. Based on the model results, soluble phosphorus concentrations consistent with secondary treatment could be achieved if WSP depth is less than 2 m. The model demonstrated a robust method to predict whether a microalgae bloom will occur under a range of model parameters.

Predicting attenuation of solar radiation (UV-B, UV-A and PAR) in waste stabilization ponds under Sahelian climatic conditions.

Because of its importance in pathogen removal and algal productivity in waste stabilization ponds, sunlight penetration was measured in microcosms and in situ under Sahelian climatic conditions. The different wavelengths were detected using a submersible radiometer equipped with three sensors: UV-B (311 nm), UV-A (369 nm) and photosynthetically available radiation (PAR, 400-700 nm). UV-B was more attenuated than UV-A and PAR. Facultative pond was more light-attenuating than maturation pond. The mean euphotic depths for UV-B were 0.20 and 0.31 m, respectively, in the facultative and maturation ponds; PAR penetrated deeper with mean euphotic depths of 0.27 and 0.42 m, respectively. The mean Secchi depths were 0.16 and 0.10 m in the maturation and facultative ponds waters, respectively. In view of the reported results, the contribution of the deeper sections of ponds to pathogen removal mediated by sunlight seems negligible. Therefore, when designing WSPs, these findings should be considered to increase the penetration of damaging wavelengths in order to ensure efficient microbial removal. For more pathogen elimination, downstream shallow ponds could be considered. The paper also shows how suspended solids, turbidity, and Secchi depth are related to the attenuation coefficients and euphotic depths. The developed models could be used to predict light penetration and then algal growth and pathogen removal mediated by sunlight in waste stabilization ponds located in Sahelian climate.

Modeling Nitrogen Dynamics in a Waste Stabilization Pond System Using Flexible Modeling Environment with MCMC.

This study presents an approach for obtaining realization sets of parameters for nitrogen removal in a pilot-scale waste stabilization pond (WSP) system. The proposed approach was designed for optimal parameterization, local sensitivity analysis, and global uncertainty analysis of a dynamic simulation model for the WSP by using the R software package Flexible Modeling Environment (R-FME) with the Markov chain Monte Carlo (MCMC) method. Additionally, generalized likelihood uncertainty estimation (GLUE) was integrated into the FME to evaluate the major parameters that affect the simulation outputs in the study WSP. Comprehensive modeling analysis was used to simulate and assess nine parameters and concentrations of ON-N, NH3-N and NO3-N. Results indicate that the integrated FME-GLUE-based model, with good Nash-Sutcliffe coefficients (0.53-0.69) and correlation coefficients (0.76-0.83), successfully simulates the concentrations of ON-N, NH3-N and NO3-N. Moreover, the Arrhenius constant was the only parameter sensitive to model performances of ON-N and NH3-N simulations. However, Nitrosomonas growth rate, the denitrification constant, and the maximum growth rate at 20 °C were sensitive to ON-N and NO3-N simulation, which was measured using global sensitivity.