On-site treatment of flowback and produced water from shale gas hydraulic fracturing: A review and economic evaluation.

On-site flowback treatment systems are typically rated and selected based on three fundamental categories: satisfying customer needs (e.g. meeting effluent quality, capacity, delivery time and time required to reach stable and steady effluent quality), common features comparison (e.g. treatment costs, stability of operation, scalability, logistics, and maintenance frequency) and through substantial product differentiation such as better service condition, overcoming current market limitations (e.g. fouling, salinity limit), and having lower environmental footprints and emissions. For treatment of flowback, multiple on-site treatment systems are available for primary separation (i.e. reducing TSS concentrations and particle size below 25 µm for disposal), secondary separation (i.e. removing TSS, iron and main scaling ions, and reducing particle size up to 5 µm for reuse), or tertiary treatment (i.e. reducing TDS concentration in the permeate/distillate to below 500 mg/L) for recycling or discharge. Depending on geographic features, frac-fluid characteristics, and regulatory aspects, operators may choose disposal or reuse of flowback water. Among these approaches, desalination is the least utilized option while in the majority of cases on-site basic separation is selected which can result in savings up to $306,800 per well. Compared to desalination systems, basic separation systems (e.g. electrocoagulation, dissolved air floatation) have higher treatment capacity (159-4133 m3/d) and specific water treatment production per occupied space (8.9-58.8 m3/m2), lower treatment costs ($2.90 to $13.30 per m3) and energy demand, and finally generate less waste owing to their high recovery of 98-99.5%, which reduces both operator costs and environmental burdens.

Removal of inert COD and trace metals from stabilized landfill leachate by granular activated carbon (GAC) adsorption.

Landfills in Germany are currently approaching stabilization phase; as a result removal of inert organics and potentially toxic elements in the leachate is becoming a primary concern. Dissolved air floatation (DAF) at the secondary stage reduces only 27% of the residual chemical oxygen demand (COD) in the investigated treatment systems; downstream granular activated carbon (GAC) units are required to further reduce COD concentration by 40-56% to meet indirect discharge or direct discharge limits respectively. Therefore, in this study performance in terms of COD and trace metals adsorption of different types of granular activated carbon were compared over different contact times and dosages. GAC 1 with Brunauer-Emmett-Teller (BET) surface area of 719.5 ±â€¯2.1 m2/g and average pore diameter (D) of 4.81 nm was identified to be inappropriate for treatment of leachate from this landfill. GAC 2 (with BET of 1513.7 ±â€¯6.4 m2/g and D of 3.50 nm) was feasible for COD reduction from DAF-pretreated leachate, while GAC 3 (with BET of 644.5 ±â€¯2.6 m2/g and D of 5.65 nm) can be coupled either with biological step alone, or as a tertiary step after the DAF unit. Moreover, as COD is the primary remaining contaminant of interest after secondary and tertiary treatment, spectrometer probes provide a close estimation of COD concentration for use in online monitoring. Beside COD removal, GAC 3 also confirmed the effectiveness of trace metals adsorption even at trace level, as it removed 66, 64, 48, 47, 43, and 25% of copper, cobalt, chromium, manganese, nickel, and zinc, respectively.

High-rate anaerobic treatment of wastewater from soft drink industry: Methods, performance and experiences.

At an Austrian soft drink company, an expanded granular sludge bed reactor for anaerobic wastewater treatment was inoculated with sludge from paper and food industries. Detailed online monitoring and laboratory examinations were carried out during startup and subsequent phases, which included a period of inhibition after ca. 80 days during which reactor degradative performance diminished suddenly, following a period of increased effluent VFA. After dosing iron chloride (FeCl2) and micronutrients and reducing organic loading to startup levels, the reactor eventually reached efficient operation (>85% COD degradation) after a gradual recovery phase. In this work performance data both at lab and full scale are elaborated along startup, adaptation, pre-inhibition, recovery and stable phases, and correlated between scales. High rate anaerobic treatment of soft drink industry wastewater was successful in terms of COD removal efficiency and final effluent COD (∼300 mg l-1), with a startup period (including inhibition) of ca. 5 months.

Heat and Bleach: A Cost-Efficient Method for Extracting Microplastics from Return Activated Sludge.

The extraction of plastic microparticles, so-called microplastics, from sludge is a challenging task due to the complex, highly organic material often interspersed with other benign microparticles. The current procedures for microplastic extraction from sludge are time consuming and require expensive reagents for density separation as well as large volumes of oxidizing agents for organic removal, often resulting in tiny sample sizes and thus a disproportional risk of sample bias. In this work, we present an improved extraction method tested on return activated sludge (RAS). The treatment of 100 ml of RAS requires only 6% hydrogen peroxide (H2O2) for bleaching at 70 °C, followed by density separation with sodium nitrate/sodium thiosulfate (SNT) solution, and is completed within 24 h. Extracted particles of all sizes were chemically analyzed with confocal Raman microscopy. An extraction efficiency of 78 ± 8% for plastic particle sizes 20 µm and up was confirmed in a recovery experiment. However, glass shards with a diameter of less than 20 µm remained in the sample despite the density of glass exceeding the density of the separating SNT solution by 1.1 g/cm3. This indicates that density separation may be unreliable for particle sizes in the lower micrometer range.

Virus elimination in activated sludge systems: from batch tests to mathematical modeling.

A virus tool based on Activated Sludge Model No. 3 for modeling virus elimination in activated sludge systems was developed and calibrated with the results from laboratory-scale batch tests and from measurements in a municipal wastewater treatment plant (WWTP). The somatic coliphages were used as an indicator for human pathogenic enteric viruses. The extended model was used to simulate the virus concentration in batch tests and in a municipal full-scale WWTP under steady-state and dynamic conditions. The experimental and modeling results suggest that both adsorption and inactivation processes, modeled as reversible first-order reactions, contribute to virus elimination in activated sludge systems. The model should be a useful tool to estimate the number of viruses entering water bodies from the discharge of treated effluents.

A mass balance approach to the fate of viruses in a municipal wastewater treatment plant during summer and winter seasons.

In contrast to previous discussion on general virus removal efficiency and identifying surrogates for human pathogenic viruses, this study focuses on virus retention within each step of a wastewater treatment plant (WWTP). Additionally, the influence of weather conditions on virus removal was addressed. To account for the virus retention, this study describes a mass balance of somatic coliphages (bacterial viruses) in a municipal WWTP, performed in the winter and summer seasons of 2011. In the winter season, the concentration of coliphages entering the WWTP was about 1 log lower than in summer. The mass balance in winter revealed a virus inactivation of 85.12 ± 13.97%. During the summer season, virus inactivation was significantly higher (95.25 ± 3.69%, p-value <0.05), most likely due to additional virus removal in the secondary clarifier by insolation. Thus, a total removal of coliphages of about 2.78 log units was obtained in summer compared to 1.95 log units in winter. Rainfall events did not statistically correlate with the concentrations of coliphages entering the WWTP in summer.

Nitrous oxide formation during nitritation and nitrification of high-strength wastewater.

The purpose of this study was to investigate the formation of nitrous oxide (N2O) in nitritation and nitrification under stable, comparable and not limiting conditions typical for treatment of high-strength wastewater. A laboratory-scale aerated chemostat was operated with reject water at different sludge retention times, achieving suppression of nitrate formation by wash-out of nitrite-oxidizing bacteria for nitritation. The N2O formation factor during stable nitritation was higher (2.90% N2O-N /NH4(-)-Nox) than during nitrification (0.74%). The positive correlation of N2O formation rates and ammonium oxidation rates was linear and thus did not contribute to changes of the N2O formation factor. The dominant factor for N2O formation during stable operation was high nitrite concentration, which was positively correlated with N2O formation rates. The highest formation factors were observed during a transition phase from nitrification to nitritation with unstable process conditions (4.81%) and during a short-term experiment with increased pH of 7 (10.28%). The results indicate that even with operational conditions that are regarded favourable for the process of nitritation N2O formation can be limited but not avoided.

Effect of substrate availability on nitrous oxide production by deammonification processes under anoxic conditions.

Due to its high global warming potential, nitrous oxide (N(2)O) emissions from wastewater treatment processes have recently received a high degree of attention. Nevertheless, there is still a lack of information regarding the microbiological processes leading to N(2)O production. In this study, two lab-scale sequencing batch reactors were operated with deammonification biomass to investigate the role of denitrification and the influence of substrate availability regarding N(2)O formation during the anoxic phase of deammonification. Three different operational phases were established: within the first phase conversion by anammox was favoured and after a transition phase, denitrification activity was promoted. Low nitrous oxide production was observed during stable operation aiming for anammox conversion. Pulsed inflow of the wastewater containing ammonium (NH(4)(+)) and nitrite (NO(2)(-)) led to increased N(2)O production rates. Within the period of denitrification as dominating nitrogen conversion process, the nitrous oxide concentration level was higher during continuous inflow conditions, but the reaction to pulsed inflow was less pronounced. The results indicated that denitrification was responsible for N(2)O formation from the deammonification biomass. Operational settings to achieve suppression of denitrification processes to a large extend were deducted from the results of the experiments.

Removal of bacterial fecal indicators, coliphages and enteric adenoviruses from waters with high fecal pollution by slow sand filtration.

The aim of the present study was to estimate the performance of slow sand filtration (SSF) facilities, including the time needed for reaching stabilization (maturation), operated with surface water bearing high fecal contamination, representing realistic conditions of rivers in many emerging countries. Surface water spiked with wastewater was infiltrated at different pore water velocities (PWV) and samples were collected at different migration distances. The samples were analyzed for phages and to a lesser extent for fecal bacteria and enteric adenoviruses. At the PWV of 50 cm/d, at which somatic phages showed highest removal, their mean log(10) removal after 90 cm migration was 3.2. No substantial differences of removal rates were observed at PWVs between 100 and 900 cm/d (2.3 log(10) mean removal). The log(10) mean removal of somatic phages was less than the observed for fecal bacteria and tended more towards that of enteric adenoviruses This makes somatic phages a potentially better process indicator than Escherichia coli for the removal of viruses in SSF. We conclude that SSF, and by inference in larger scale river bank filtration (RBF), is an excellent option as a component in multi-barrier systems for drinking water treatment also in areas where the sources of raw water are considerably fecally polluted, as often found in many emerging countries.

Long-term simulation of the activated sludge process at the Hanover-Gümmerwald pilot WWTP.

The aim of this study was to obtain a validated model, consisting of the Activated Sludge Model No. 3 (ASM3) and the EAWAG bio-P module, which could be used as a decision tool for estimating the maximum allowable peak flow to wastewater treatment plants during stormwater conditions. The databases used for simulations originated from the Hanover-Gummerwald pilot plant subjected to a series of controlled, short-term hydraulic shock loading experiments. The continuous influent wastewater composition was generated using on-line measurements of only three parameters (COD, N-NH4+, P-PO4 3-). Model predictions were compared with on-line data from different locations in the activated sludge system including the aerobic zone (concentrations of N-NH4+, N-NO3-) and secondary effluent (concentrations of P-PO4 3-). The simulations confirmed experimental results concerning the capabilities of the system for handling increased flows during stormwater events. No (or minor) peaks of N-NH4+ were predicted for the line with the double dry weather flowrate, whereas peaks of N-NH4+ at the line with the quadruple dry weather flowrate were normally exceeding 8 g Nm(-3) (similar to the observations).