A sustainable approach to enhance heavy hydrocarbons removal in landfarming treatment.

The present study aimed to evaluate the best strategy to enhance the degradation rate of heavy petroleum hydrocarbons (HPH) contaminated soil in a landfarming plant. Samples of real contaminated soil, further spiked with HPH, were treated in mesocosm reactors simulating the landfarming system. One reactor was operated without any modification compared to the real landfarming plant. The other three reactors were operated with different strategies to improve the removal rate: biostimulation (BS) through the addition of nitrogen and phosphorus; bioaugmentation (BA) with the inoculation of sludge produced in the treatment of the process water from the oil re-fining plant of the same industrial area; combination of biostimulation and bioaugmentation (BAS). The biostimulation (BS) was the most effective strategy, leading to a reduction of the remediation time by 35% as compared to the traditional treatment. Bioaugmentation (BA) also provided positive effects leading to a reduction of the remediation time by 24%; its performance improved further when the addition of sludge was combined with the increase of phosphorous (BAS). Therefore, the key tool was represented by the phosphorous availability, whereas the application of sludge was most useful to provide waste with a new possibility of reuse, thus fulfilling the principles of the circular economy. The final characterization showed that the treated soil was suitable for reuse in industrial areas according to the legislation in force.

A step forward on site-specific environmental risk assessment and insight into the main influencing factors of CECs removal from wastewater.

The presence of Contaminants of Emerging Concern (CECs) in water systems has been recognized as a potential source of risk for human health and the ecosystem. The present paper aims at evaluating the effects of different characteristics of full-scale Wastewater Treatment Plants (WWTPs) on the removal of 14 selected CECs belonging to the classes of caffeine, illicit drugs and pharmaceuticals. Particularly, the investigated plants differed because of the treatment lay-out, the type of biological process, the value of the operating parameters, the fate of the treated effluent (i.e. release into surface water or reuse), and the treatment capacity. The activity consisted of measuring concentrations of the selected CECs and also traditional water quality parameters (i.e. COD, phosphorous, nitrogen species and TSS) in the influent and effluent of 8 plants. The study highlights that biodegradable CECs (cocaine, methamphetamine, amphetamine, benzoylecgonine, 11-nor-9carboxy-Δ9-THC, lincomycin, trimethoprim, sulfamethoxazole, sulfadiazine, sulfadimethoxine, carbamazepine, ketoprofen, warfarin and caffeine) were well removed by all the WWTPs, with the best performance achieved by the MBR for antibiotics. Carbamazepine was removed at the lowest extent by all the WWTPs. The environmental risk assessed by using the site-specific value of the dilution factor resulted to be high in 3 out of 8 WWTPs for carbamazepine and less frequently for caffeine. However, the risk was reduced when the dilution factor was assumed equal to the default value of 10 as proposed by EU guidelines. Therefore, a specific determination of this factor is needed taking into account the hydraulic characteristics of the receiving water body.

Physical-Chemical Characterization of Different Carbon-Based Sorbents for Environmental Applications.

Biochar has been used in various applications, e.g., as a soil conditioner and in remediation of contaminated water, wastewater, and gaseous emissions. In the latter application, biochar was shown to be a suitable alternative to activated carbon, providing high treatment efficiency. Since biochar is a by-product of waste pyrolysis, its use allows for compliance with circular economics. Thus, this research aims to obtain a detailed characterization of three carbonaceous materials: an activated carbon (CARBOSORB NC 1240®) and two biochars (RE-CHAR® and AMBIOTON®). In particular, the objective of this work is to compare the properties of three carbonaceous materials to evaluate whether the application of the two biochars is the same as that of activated carbon. The characterization included, among others, particle size distribution, elemental analysis, pH, scanning electron microscope, pore volume, specific surface area, and ionic exchange capacity. The results showed that CARBOSORB NC 1240® presented a higher specific surface (1126.64 m2/g) than AMBIOTON® (256.23 m2/g) and RE-CHAR® (280.25 m2/g). Both biochar and activated carbon belong to the category of mesoporous media, showing a pore size between 2 and 50 nm (20-500 Å). Moreover, the chemical composition analysis shows similar C, H, and N composition in the three carbonaceous materials while a higher O composition in RE-CHAR® (9.9%) than in CARBOSORB NC 1240 ® (2.67%) and AMBIOTON® (1.10%). Differences in physical and chemical properties are determined by the feedstock and pyrolysis or gasification temperature. The results obtained allowed to compare the selected materials among each other and with other carbonaceous adsorbents.

Impact of COVID19 restrictions on organic micropollutants in wastewater treatment plants and human consumption rates.

COVID19 pandemic and the consequent restrictions to constrain SARS-CoV-2 spreading produced several impacts on the worldwide population. The present study focused on 10 Organic Micropollutants (illicit drugs, pharmaceuticals including some antibiotics and caffeine) and aimed to assess: (1) if COVID19 pandemic restrictions affected the load of those contaminants released into the sewage network and consequently the removal achieved by the Wastewater Treatment Plants; (2) if pursuant to the COVID19 pandemic, there was a change in population consumption rates of the same compounds through the wastewater-based epidemiology (WBE) approach. Two full-scale wastewater treatment plants (WWTPs) located in Central Italy were chosen as case studies, which are distinguished by different characteristics of the catchment area and water treatment layouts. The study was based on a 2-years monitoring activity of the concentration of the above organic micropollutants, traditional water quality parameters (COD, TSS, nitrogen compounds, total phosphorous) and flow rate in the influent and effluent. The statistical analysis of the monitoring data showed an increase of the influent load of most of the organic micropollutants. A decrease from 22% to -18% of the median removal efficiency was observed for carbamazepine in the WWTP with the lower treatment capacity only. The other compounds were removed roughly at the same rate. The application of the WBE approach demonstrated an increase in the consumption rate of cocaine, trimethoprim, sulfamethoxazole, sulfadiazine, carbamazepine and above all caffeine during the COVID19 restrictions period. These results highlight that COVID19 pandemic affected people's lifestyle and habits also as far as drugs consumption is concerned, which in turn might have an impact on the treatment efficacy of plants and finally on the receiving water body quality. Therefore, it is mandatory to keep monitoring to improve knowledge and eventually to implement the required measures to address this new problem.

Technical-economic comparison of chemical precipitation and ion exchange processes for the removal of phosphorus from wastewater.

Chemical precipitation with the addition of ferric chloride is commonly used to remove phosphorus from wastewater. However, since its application also involves several disadvantages, alternative solutions are required. The present paper shows the results of a full-scale experimental work aimed at evaluating the efficiency of the ion exchange process using a polymeric anion exchange resin impregnated with aluminum ions in the removal of phosphorus from wastewater. The study compared the results obtained through this process with chemical precipitation, considering both technical and economic issues. At the same dosage of 6 L/hour and influent concentration (about 6 mg/L), total removal efficiency of 95% and 78% (including also that occurring in the mechanical and biological processes) was achieved by means of the anion exchange process and chemical precipitation, respectively. However, in the latter case, this value was insufficient to ensure consistent compliance with the limit of 2 mg/L Ptot set on the effluent; to achieve this goal, the ferric chloride dosage had to be raised to 12 L/hour, thus increasing the related costs. Furthermore, the anion exchange process generated a lower sludge production. Therefore, the ion exchange process represents a valid alternative to chemical precipitation for P removal from wastewater.

Effects of low-dosage ozone pre-treatment on the anaerobic digestion of secondary and mixed sludge.

The present study investigated the effects of ozonation pre-treatment at low-ozone dosage (below 100 mgO3/gTS0) with respect to previous studies, on the anaerobic digestion of waste-activated sludge alone and a mixture of activated sludge and primary sludge. Methane production and volatile suspended solids reduction efficiency were determined for different specific ozone dosages and compared with the values obtained in the absence of pre-treatment. Among the dosages tested in the study (from 4.8 to 73.2 mgO3/gTS0 for mixed sludge and from 3.5 to 53.6 mgO3/gTS0 for waste-activated sludge), the best results were obtained at the lowest ones: 4.8 and 3.5 mgO3/gTS0 for mixed sludge and waste-activated sludge, respectively. Indeed, at this dosage, an additional methane production of about 6% and 30% was achieved for mixed and waste-activated sludge, respectively; furthermore, the maximum CH4 production rate increased of about 21% and 33% for mixed and waste-activated sludge, respectively. With respect to the Gompertz model, the modified logistic model provided the best agreement to the experimental data of the specific methane yield production. The present study demonstrated the importance of investigating the application of low dosages when ozonation is being evaluated as a pre-treatment to enhance anaerobic digestion performance.

A laboratory-study on the analytical determination and removal processes of THC-COOH and bezoylecgonine in the activated sludge reactor.

The present study focused on 11-nor-9carboxy-Δ9-THC (THC-COOH) and Benzoylecgonine (BE), the most common metabolites of cannabis and cocaine, respectively, present in the domestic sewage entering the wastewater treatment plants. The aims of the study were: (1) to validate the analytical method of detection in wastewater and sludge; (2) to determine contribution of biodegradation and other processes to the removal in the biological reactor of the wastewater treatment plant (WWTP) and the response of biomass to different drug concentrations. The Ultra-Performance Liquid Chromatography coupled to tandem Mass Spectrometry method showed to be repeatable and reliable (recovery>75%; repeatability<10-15%; bias uncertainty<10) for measurements in wastewater; the ultrasound assisted extraction (USE) demonstrated to be reliable as pre-treatment of activated sludge solid phase. Both drugs were fully removed from the liquid phase in the lab-scale biological reactor within 24 h. Biodegradation was the main BE removal mechanism, and the first order kinetic model provided the best fitting of the experimental data. THC-COOH was mainly removed due to a combination of adsorption and biodegradation; adsorption was better described by the pseudo-second order kinetic model and the Freundlich isotherm. Both drugs at the higher concentrations caused inhibition of nitrogen oxidation and carbon removal.

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.

A study through batch tests on the analytical determination and the fate and removal of methamphetamine in the biological treatment of domestic wastewater.

Methamphetamine (MET) is one of the most used illicit drugs in Europe and is recognized as one of the Emerging Organic Micropollutants. It is discharged into the sewerage system from different sources and then enters the wastewater treatment plants. The present study aimed at providing a better knowledge of the fate of MET through the wastewater treatment plants. The study addressed two different issues: (1) optimization of the analytical methods for MET determination in both liquid and sludge phases, focusing on the effects of potentially interfering substances and (2) investigation on the behaviour of MET in the biological treatment process, with specific concern for the biomass activity at different drug concentrations. Results of the study on issue 1 highlighted that the applied analytical method for MET determination (UPLC-MS/MS) is affected by the main components of wastewater for about 9-23%, which is comparable with the uncertainties of the method (about ± 28%). The method showed also to be repeatable and reliable (recovery > 75%; repeatability < 10-15%; bias uncertainty < 30%), and relatively easy-to-use. Therefore, it can be considered suitable for measurements on routine base in the WWTPs. Batch tests conducted to address issue 2 showed total removal of 84, 90, and 96% at 50, 100, and 200 ng/L initial MET concentration, respectively, for a contact time of 6 h. The removal process was mainly ascribed to the biological activity of both heterotrophic and autotrophic bacteria. The pseudo first-order kinetic model provided the best fitting of the experimental data of the overall biological processes at all the tested concentrations. Furthermore, the respirometric tests showed that MET does not induce any inhibition. Adsorption of MET on activated sludge was always very low.

Sludge reduction in a small wastewater treatment plant by electro-kinetic disintegration.

Sludge reduction in a wastewater treatment plant (WWTP) has recently become a key issue for the managing companies, due to the increasing constraints on the disposal alternatives. Therefore, all the solutions proposed with the aim of minimizing sludge production are receiving increasing attention and are tested either at laboratory or full-scale to evaluate their real effectiveness. In the present paper, electro-kinetic disintegration has been applied at full-scale in the recycle loop of the sludge drawn from the secondary settlement tank of a small WWTP for domestic sewage. After the disintegration stage, the treated sludge was returned to the biological reactor. Three different percentages (50, 75 and 100%) of the return sludge flow rate were subjected to disintegration and the effects on the sludge production and the WWTP operation efficiency evaluated. The long-term observations showed that the electro-kinetic disintegration was able to drastically reduce the amount of biological sludge produced by the plant, without affecting its treatment efficiency. The highest reduction was achieved when 100% return sludge flow rate was subjected to the disintegration process. The reduced sludge production gave rise to a considerable net cost saving for the company which manages the plant.

Techno-economic evaluation of the application of ozone-oxidation in a full-scale aerobic digestion plant.

This paper deals with the application of the ozone-oxidation in a full scale aerobic sludge digester. Ozonation was applied continuously to a fraction of the biological sludge extracted from the digestion unit; the ozonated sludge was then recirculated to the same digester. Three different ozone flow rates were tested (60,500 and 670g O3 h(-1)) and their effects evaluated in terms of variation of the total and soluble fractions of COD, nitrogen and phosphorous, of total and volatile suspended solids concentrations and Sludge Volume Index in the aerobic digestion unit. During the 7-month operation of the ozonation process, it was observed an appreciable improvement of the aerobic digestion efficiency (up to about 20% under the optimal conditions) and of the sludge settleability properties. These results determined an average reduction of about 60% in the biological sludge extracted from the plant and delivered to final disposal. A thorough economic analysis showed that this reduction allowed to achieve a significant cost saving for the plant with respect to the previous years operated without ozonation. Furthermore, it was determined the threshold disposal cost above which implementation of the ozone oxidation in the aerobic digestion units of similar WWTPs becomes economically convenient (about 60€t(-1) of sludge).

Technical-economical analysis of selected decentralized technologies for municipal wastewater treatment in the city of Rome.

Several wastewater treatment technologies were evaluated as alternative systems to the more traditional centralized continuous flow system to serve decentralized areas of the city of Rome (Italy). For instance, the following technologies were selected: (1) Constructed wetlands, (2) Membrane Biological Reactor, (3) Deep Shaft, (4) Sequencing Batch Reactor, and (5) Combined Filtration and UV-disinfection. Such systems were distinguished based on the limits they are potentially capable of accomplishing on the effluent. Consequently, the SBR and DS were grouped together for their capability to comply with the standards for the discharge into surface waters (according to the Italian D.Lgs. 152/06, Table 1, All. 5), whereas the MBR and tertiary system (Filtration+UVc-disinfection) were considered together as they should be able to allow effluent discharge into soil (according to the Italian D.Lgs. 152/06, Table 4, All. 5) and/or reuse (according to the Italian D.M. 185/03). Both groups of technologies were evaluated in comparison with the more common continuous flow treatment sequence consisting of a biological activated sludge tank followed by the secondary settlement, with final chlorination. CWs were studied separately as a solution for decentralized urban areas with limited population. After the analysis of the main technical features, an economical estimate was carried out taking into account the investment, operation and maintenance costs as a function of the plant's capacity. The analysis was based on real data provided by the Company who manages the entire water system of the City of Rome (Acea Ato 2 S.p.A.). A preliminary design of the treatment plants using some of the selected technologies was finally carried out.

Biological treatment of PAH-contaminated sediments in a Sequencing Batch Reactor.

The technical feasibility of a sequential batch process for the biological treatment of sediments contaminated by polycyclic aromatic hydrocarbons (PAHs) was evaluated through an experimental study. A bench-scale Sediment Slurry Sequencing Batch Reactor (SS-SBR) was fed with river sediments contaminated by a PAH mixture made by fluorene, anthracene, pyrene and crysene. The process performance was evaluated under different operating conditions, obtained by modifying the influent organic load, the feed composition and the hydraulic residence time. Measurements of the Oxygen Uptake Rates (OURs) provided useful insights on the biological kinetics occurring in the SS-SBR, suggesting the minimum applied cycle time-length of 7 days could be eventually halved, as also confirmed by the trend observed in the volatile solid and total organic carbon data. The removal efficiencies gradually improved during the SS-SBR operation, achieving at the end of the study rather constant removal rates above 80% for both 3-rings PAHs (fluorene and anthracene) and 4-ring PAHs (pyrene and crysene) for an inlet total PAH concentration of 70 mg/kg as dry weight (dw).

Technical and experimental evaluation of an innovative decentralized technology for the municipal wastewater treatment in the city of Rome.

The present paper shows the results obtained through an experimental activity carried out on a pilot-scale plant using an innovative technology which couples the granular aerobic sludge with the sequencing batch process. Treatment efficiency and operation costs were evaluated in order to assess feasibility of this new technology for the upgrading of the existing continuous flow activated sludge treatment plant located in Casal Monastero, a decentralized area of the City of Rome. During start-up (about 3 months), the granular aerobic sludge was developed by controlling the dissolved oxygen concentration, the value of pH and the up-flow velocity. Besides, the influent organic loading was progressively increased starting from 0.1 kg/m³ d up to 0.9 kg/m³ d. In order to improve nitrogen removal, an anoxic phase was temporary added to the operative cycle. Complete development of the granular sludge determined an appreciable improvement of the denitrification process which allowed to eliminate the anoxic phase. At regime conditions, the plant was operated with 3 daily cycles, each one of 8 h. The new system showed a reduced sludge production (of about 20-35%) as compared to the existing plant, along with high removal efficiency of both Chemical Oxygen Demand (COD) and nitrogen. However, the operation was discontinuous and strictly related to the strength of the granular sludge. Therefore, a careful monitoring is recommended in order to control operation and performance of this new system.

Pretreated waste landfilling: relation between leachate characteristics and mechanical behaviour.

The present paper presents a part of a wider research effort aiming at studying the long-term behaviour of different pre-treated wastes once landfilled; in particular, this paper deals with the analysis of settlements and their correlation with the main leachate biochemical parameters (BOD, COD and pH). The municipal solid waste organic fraction (MSWOF) and bottom ash (BA) from incineration of municipal solid waste (MSW) were considered in the study and used to set up different semi-pilot landfill plants. Particularly, the FT plant contained 90 days aerobically biostabilized MSWOF, the FP plant was filled with 15 days aerobically biostabilized MSWOF and the MX plant with a 30-70% (by weight) mixture of BA and the same MSWOF used in the FP plant. The data obtained showed a faster mechanical and biological stabilization of the FT and MX plants, due to the less biodegradable organic fraction content initially present in the FT plant and to the presence of BA, having a stabilizing effect, in the MX plant. Besides, similar behaviour of FT and MX was observed, and also a strong correlation between the settlement and the biochemical parameters time profiles was identified.