Fate of selected drugs in the wastewater treatment plants (WWTPs) for domestic sewage

The wide diffusion of Emerging Organic Micropollutants (EOMs) in the environment is receiving increasing attention due to their potential toxicological effects on living organisms. So far, the Wastewater Treatment Plants (WWTPs) have not been designed with the purpose to remove these contaminants; therefore, they can represent the major source of release into the environment both through the effluent and the wasted sludge. The fate of EOMs in the WWTPs is still not completely known; further investigations are therefore needed to assess if it is possible to exploit the existing treatment units to reduce EOM concentrations or which processes must be implemented to this purpose. Among the wide class of EOMs, the present study focused on the following drugs of abuse: amphetamine (AM), methamphetamine (MET), 11-nor-Δ9-THC-9carboxy (THC-COOH) and benzoylecgonine (BEG). Presence and removal efficiency of these drugs in the activated sludge tank of a WWTP for domestic sewage was investigated through analyses at both full-scale and laboratory scale. Determinations conducted in the full-scale WWTP highlighted that, among the searched drugs, AM was found to be the most abundant in the influent and effluent of the biological oxidation tank, while 11-nor-Δ9-THC-9carboxy was present at the lowest concentration. Some removal took place in the units prior to the oxidation tank, although the main reduction was observed to occur in the biological oxidation reactor. All the drugs showed a wide variability of the measured concentrations during the week and the day. Taking into account results from both full-scale observations and batch tests, removals in the biological reactor were found within the following ranges: 33–84% for AM, 33–97% for MET, 33–57% for BEG and 29–83% for THC-COOH. These removals were due to a combination of adsorption and biodegradation mainly, while volatilization did not play a significant role. Other processes, e.g. hydrolysis, were likely to occur. © 2017 Springer-Verlag Berlin Heidelber

Performance of Italian zeolitic tuffs and pozzolana in 2-chlorophenol removal from contaminated groundwater. Lab-scale experience

The physical and chemical properties of zeolites and the availability of localized deposits of naturally occurring zeolitized tuffs and pozzolana, make them desirable for and applicable to the remediation of contaminated groundwater. This paper documents the results of a laboratory study to test the capacity of native Italian zeolites to remove 2-chlorophenol (2-CP) from water. Italian zeolitic tuff and pozzolana were characterized in terms of their chemical and structural properties and of their adsorption capacities. Moreover, the experimental activity investigated their adsorption behaviour: time and pH dependence of the adsorption process was evaluated. The results of the time-dependence adsorption study under a constantly stirred condition showed that the adsorption increases with a longer contact time for all samples; the highest adsorption occurred at pH=8 divided by 8.5. Due to the good removal efficiencies obtained, a column test simulating the condition of an in situ permeable reactive barrier was carried out, in order to estimate the removal kinetics and the long-term behaviour. The removal efficiencies reached values higher than 90%, even if some long-term performance worsening occurred, due to the progressive exhaustion of the adsorption sites. These experiments demonstrate the capacity of naturally occurring zeolites to remove 2-CP from water and the opportunity to make economic use of these native deposits for in situ groundwater remediation

Magnetic core nanoparticles coated by titania and alumina for water and wastewater remediation from metal contaminants

Nanomaterials have been widely used for remediation of contaminated streams. However, using nanomaterials within water and wastewater might be dangerous since fate and health impact of nanoparticles is still unknown. Therefore, it is mandatory to avoid contamination by removing all the nanoparticles from the treated stream. This can be performed by immobilizing the nanoparticles on supports, although this approach leads to lower efficiency values. Another possibility is to use suspended nanoparticles: in this case, efficiency of the treatment process is enhanced. If nanomaterials have a magnetic core-shell, then suspended nanoparticles can be removed in a safe and easy was by using magnetic traps. In the present study, new nanomaterials based on magnetic core-shell structure were developed: the magnetic core guarantees a complete removal from the treated water and wastewater streams, whereas the shell (coating) is functionalized to eliminate specific classes of pollutants. A first experimental step allowed to produce the magnetic nanoparticles and perform a coating with SiO2 in order to electrically isolate the core from the ambient and to avoid degradation. This procedure is well established and the production of SiO2 coated magnetic nanoparticles are nowadays a validated procedure by using a spinning disk reactor.In a successive step, the silica shell magnetic cores were coated by titania and/or activated alumina particles with the aim of removing metals by adsorption. In the present study, the arsenic adsorption capacity of silica shell magnetic cores nanoparticles coated by titania and/or activated was investigated through kinetic experiments. All the tested adsorbents performed very well showing very rapid rates of the adsorption process. Among them, the best performing media were found to be those with titania coating. The best fitting kinetic model was found to be the pseudo-second order one for all of the adsorbents

Remediation of Lead-Contaminated Water by Virgin Coniferous Wood Biochar Adsorbent. Batch and Column Application

In this paper, RE-CHAR® biochar, produced by a wood biomass pyrolysis process, which is usually applied as a soil fertilizer, was investigated for a novel use, that was as adsorbent for remediating a lead-contaminated solution. Firstly, a deep physical and chemical characterization of RE-CHAR® biochar was carried out. Then, the adsorption capacity of lead from 50 to 100 mg/L solutions was determined under batch and continuous flow conditions. Kinetics of the batch adsorption process were very rapid and complete removal was achieved within 4-h contact time at both Pb concentrations, using a biochar dosage of 5 g/L. These data were best fitted by the pseudo-second-order model, with the rate constant and the equilibrium capacity equal to ks = 0.0091 g/min and qe = 9.9957 mg/g at 50 mg/L Pb and ks = 0.0128 g/min and qe = 20.1462 mg/g at 100 mg/L Pb, respectively. The Langmuir isotherm model best fitted the equilibrium data at both Pb concentrations, with the Langmuir constant and maximum adsorption capacity equal to b = 11.5804 L/mg and qmax = 4.6116 mg/g at 50 mg/L Pb and b = 2.8933 L/mg and qmax = 9.5895 mg/g at 100 mg/L Pb. Continuous flow column tests showed that adding biochar to the soil of the adsorbent bed significantly extended the breakthrough and exhaustion times, with respect to the column filled with soil only. The Thomas model best fitted the experimental data of the breakthrough curves, with the constant kTH = 5.28 × 10−5 mL/min/mg and the maximum adsorption capacity q0 = 334.57 mg/g which was comparable to the values reported for commercial adsorbents. Based on these results, it can be assessed that RE-CHAR® biochar can be used as an effective adsorbent for lead removal from water solutions even at high concentrations

Study of the performance of disinfection with sodium hypochlorite on a full-scale sewage treatment plant

A full-scale sewage treatment plant was investigated to assess the performance of the disinfection stage. Sodium hypochlorite was used as a disinfectant agent and the process efficiency was evaluated by E.coli removal. The research took place over a period of two years in order to evaluate the effect of retention time (t) and residual chlorine (Cr) under different seasonal conditions. The effectiveness of E.coli removal with sodium hypochlorite proved to be strictly dependent on the factor CR t (product of residual chlorine with the contact time). The regression line of the experimental points was, on the whole, well comparable with the model proposed by Collins, especially in the field of CRt lower than 30 mg L-1 min

Mass balance of emerging organic micropollutants in a small wastewater treatment plant

Emerging organic micropollutants are compounds measured in water in μg/l or ng/l which may have long-term negative effects on both wildlife and humans. The purpose of this work was to perform a mass balance of emerging organic micropollutants on activated sludge tank and on secondary settling tank in a small wastewater treatment plant in the Municipality of Rome. The analytes monitored in this work were: Estrone (E1), 17β-Estradiol (E2) and 17α- Ethinylestradiol (EE2) for steroid hormones, 4-Nonylphenol (4-NP) and Bisphenol A (BPA) for substituted Phenols and Alkylphenols, Amphetamine (AM), Methamphetamine (MET), Benzoylecgonine (BEG) and 11-nor-Δ9-THC- 9carboxy (THC-COOH) for drugs of abuse. Mass balance on activated sludge tank showed that the emerging organic micropollutants removed were BPA (59%), EE2 (34%), AM (56%) and THCCOOH (35%). The processes occurring in the secondary settling tank were able to reduce 4-NP (26%), BPA (74%), E1 (82%), EE2 (93%), AM (44%), MET (80%), BEG (72%) and THC-COOH (39%). The residual amount of each substance was distributed between the effluent, the return sludge line and the excess sludge. Since the removal of emerging organic micropollutants was partial, the conventional wastewater treatment plant is not able to completely break down these substances. Accordingly, these compounds are found in water body potentially active and dangerous to wildlife and humans. © 201 WIT Press

Application of iron based nanoparticles as adsorbents for Arsenic removal from water

Arsenic contaminations of groundwater in several parts of the world are the results of natural and/or anthropogenic sources, and have a large impact on human health. Millions of people rely on groundwater for drinking water supply; therefore, contamination of these sources represents a strong limitation to their civil and urban development. Due to the toxicity and potential carcinogen effect, in 2001 the World Health Organization has reduced the maximum allowable concentration of arsenic in drinking water to 10 μg/L. This new limit has been then adopted by numerous countries, such as Italy. Among the methods used to reduce arsenic concentration, the adsorption process has often proved to be the most suitable in the case of drinking water sources. Adsorption efficiency strongly depends on the type of adsorbents. In the case of arsenic contaminated groundwater, a number of media have been tested so far (alumina, iron-based), some of which providing good removal. However, there is still an high interest in new media capable of providing better performances, i.e. longer duration of the column plants where the adsorption process is usually implemented at the full-scale. Recently there has been increasing interest on the application of nanoparticles and nanostructured materials as efficient and viable alternatives to conventional adsorbents in the removal of metals from water. Due to their small size, they possess a large surface area and a high surface area to volume ratio. These characteristics improve the adsorption capacity of the nanoparticles and make them potentially suitable for the application where higher removal efficiency are required. The present work investigates the application of a new nano-adsorbent for arsenic removal from water. The media was produced in laboratory and made by magnetite nanoparticles. These iron-based nanoparticles, characterized by a very small size (9 nm), showed high removal rate, providing a specific adsorption capacity at equilibrium of about 8.25 [mg As/g ads]. Among the investigated models, the pseudo-second order best fitted the experimental data of the kinetic tests. Comparisons made with the performance provided by commercial adsorbents and other materials confirms the use of magnetite nanoparticles for the removal of arsenic as a promising technique

Biohydrogen production from food waste: Influence of the inoculum-to-substrate ratio

In this study, the influence of the inoculum-to-substrate ratio (ISR) on dark fermentative hydrogen production from food waste (FW) was evaluated. ISR values ranging from 0.05 to 0.25 g VSinoculum/g VSsubstrate were investigated by performing batch tests at T = 39 °C and pH = 6.5, the latter being the optimal value identified based on a previous study. The ISR was found to affect the fermentation process, clearly showing that an adequate ISR is essential in order to optimise the process kinetics and the H2 yield. An ISR of 0.14 proved to optimum, leading to a maximum H2 yield of 88.8 L H2/kg VSFW and a maximum production rate of 10.8 L H2/kg VSFW∙h. The analysis of the fermentation products indicated that the observed highest H2 production mostly derived from the typical acetate/butyrate-type fermentation

Biodegradation of 3-chlorophenol in a sequencing batch reactor

The present paper shows the results obtained through a study on the biodegradation of 3-chlorophenol (3-CP) in a Sequencing Batch Reactor (SBR). To such a purpose a lab-scale SBR was fed a synthetic wastewater containing 3-CP and nutrients (nitrogen and phosphorus) diluted in tap water. The operating strategy, in terms of both the duration of either the cycle or the react phase, was changed throughout the experimental activity in order to find out the optimal one allowing to ensure constant and high removal efficiency despite the increasing 3-chlorophenol concentration in the feed. Biomass collected from a full-scale continuous flow activated sludge facility treating domestic wastewater was used as seed, after being acclimated to 3-CP by means of several batch tests. The results showed that a periodically operated activated sludge system can be successfully used for the biodegradation of chlorophenol compounds, after the needed members of the microbiological consortium are selected and enriched

Experimental and Numerical Study of Biochar Fixed Bed Column for the Adsorption of Arsenic from Aqueous Solutions

Two laboratory tests were carried out to verify the suitability of an Italian commercial biochar as an adsorbing material. The chosen contaminant, considered dissolved in groundwater, was As. The circular economic concept demands the use of such waste material. Its use has been studied in recent years on several contaminants. The possibility of using an efficient material at low cost could help the use of low-impact technologies like permeable reactive barriers (PRBs). A numerical model was used to derive the kinetic constant for two of the most used isotherms. The results are aligned with others derived from the literature, but they also indicate that the use of a large amount of biochar does not improve the efficiency of the removal. The particular origin of the biochar, together with its grain size, causes a decrease in contact time required for the adsorption. Furthermore, it is possible that a strong local decrease in the hydraulic conductibility does not allow for a correct dispersion of the flow, thereby limiting its efficiency