This book covers the principles and practices of processes and technologies applied for the treatment of saline wastewater with discharge and reuse purpose, and those applied for its valorisation. ...Saline wastewater was considered to present electrical conductivities over 2 mS/cm, which is the limit for crop irrigation. Saline wastewater management is described with respect to: Basics about salinity characterisation and environmental impact Effects of salinity on the wastewater physical-chemical treatments Effects of salinity on biological treatment processes Valorisation of saline wastewater for energy and materials production Technologies for saline wastewater treatment and salt recovery Urban and industrial saline wastewater treatment Treatment and Valorisation of Saline Wastewater includes two case studies evaluating the treatment of the effluents from a fish cannery and from a WWTP with seawater intrusions in the collecting system. This book is intended as a text reference book for post-graduate, PhD students and researchers interested in the effects of salinity on the wastewater treatment and valorisation processes. It also serves as a reference text for professionals working in the industrial and urban wastewater sector that deal with saline wastewater.
The performance of the partial nitritation/anammox processes was evaluated for the treatment of fish canning effluents. A sequencing batch reactor (SBR) was fed with industrial wastewater, with ...variable salt and total ammonium nitrogen (TAN) concentrations in the range of 1.75–18.00 g-NaCl L−1 and 112 - 267 mg-TAN L−1. The SBR operation was divided into two experiments: (A) progressive increase of salt concentrations from 1.75 to 18.33 g-NaCl L−1; (B) direct application of high salt concentration (18 g-NaCl L−1). The progressive increase of NaCl concentration provoked the inhibition of the anammox biomass by up to 94% when 18 g-NaCl L−1 were added. The stable operation of the processes was achieved after 154 days when the nitrogen removal rate was 0.021 ± 0.007 g N/L·d (corresponding to 30% of removal efficiency). To avoid the development of NOB activity at low salt concentrations and to stabilize the performance of the processes dissolved oxygen was supplied by intermittent aeration. A greater removal rate of 0.029 ± 0.017 g-N L−1 d−1 was obtained with direct exposure of the inoculum to 18 g-NaCl L−1 in less than 40 days. Also, higher specific activities than those from the inoculum were achieved for salt concentrations of 15 and 20 g-NaCl L−1 after 39 days of operation. This first study of the performance of the partial nitritation/anammox processes, to treat saline wastewaters, indicates that the acclimation period can be avoided to shorten the start-up period for industrial application purposes. Nevertheless, further experiments are needed in order to improve the efficiency of the processes.
•Partial nitritation/anammox SBR operated to treat saline canning effluents.•Intermittent aeration avoids NOB activity at low NaCl and nitrite accumulation.•Anammox activity loss of 94% after 160 days of salt rise from 2 to 18 g-NaCl L−1.•Direct exposure to high salt (18 g-NaCl L−1) avoids progressive anammox weakening.•Partial nitritation/anammox start-up is shortened by direct exposure to high salt.
Polyhydroxyalkanoates (PHA) appear as good candidates to substitute conventional petroleum-based plastics since they have similar properties but with the advantage of being biodegradable. Wastewater ...streams with high organic content are feasible substrates for PHA production resulting in an opportunity for waste recovery. One of the main challenges is the optimization of the selection of microorganisms with high PHA storage capacity. This microbial selection is performed in sequencing batch reactors (SBR) operated under an aerobic feast/famine (F/F) regime. In the present study, a settling stage was added at the end of the feast phase of the enrichment cycle of a SBR fed with pre-acidified cooked mussel processing wastewater (containing up to 12 g NaCl/L). Settling and subsequent supernatant discharge favoured the wash-out of non-accumulating microorganisms as well as the removal of substances that enhanced their undesired development (proteins and carbohydrates). Microbial analysis performed by fluorescence in situ hybridization (FISH) technique showed shifts in the microbial community; the presence of genus Paracoccus increased whereas genera Comamonas decreased. Moreover, the process efficiency was improved with the increase of the PHA production yield (YPHA) and the maximum PHA storage capacity (max. PHA) from 0.48 to 0.72 CmmolPHA/CmmolVFA and from 40 to 60 wt%, respectively. The polymer composition also changed, its HB:HV ratio varied from 83:17 to 70:30. Results obtained in the present study showed that settling after the feast phase promoted the removal of carbon sources that did not contribute to PHA production and the washout of non-storing bacteria, which favoured the culture enrichment.
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•Complex saline industrial wastewater as a substrate for PHA production.•A settling stage was included in the enrichment cycle after VFA consumption.•Proteins and carbohydrates promoting growth instead of PHA production were removed.•The PHA production yield increased from 0.48 to 0.72 CmmolPHA/CmmolVFA.•The maximum PHA storage capacity of the MMC improved from 40 to 60 wt%.
•Nitrogen removal in the main stream of the WWTPs to improve the energetic efficiency.•The application of Anammox based processes can save 28% of costs.•Nitrite oxidation is the main drawback to ...apply those processes to the main stream.
Nowadays the application of Anammox based processes in the wastewater treatment plants has given a step forward. The new goal consists of removing the nitrogen present in the main stream of the WWTPs to improve their energetic efficiencies. This new approach aims to remove not only the nitrogen but also to provide a better use of the energy contained in the organic matter. The organic matter will be removed either by an anaerobic psychrophilic membrane reactor or an aerobic stage operated at low solids retention time followed by an anaerobic digestion of the generated sludge. Then ammonia coming from these units will be removed in an Anammox based process in a single unit system. The second strategy provides the best results in terms of operational costs and would allow reductions of about 28%.
Recent research works performed on Anammox based processes and operated at relatively low temperatures and/or low ammonia concentrations were carried out in single-stage systems using biofilms, granules or a mixture of flocculent nitrifying and granular Anammox biomasses. These systems allowed the appropriated retention of Anammox and ammonia oxidizing bacteria but also the proliferation of nitrite oxidizing bacteria which seems to be the main drawback to achieve the required effluent quality for disposal. Therefore, prior to the implementation of the Anammox based processes at full scale to the water line, a reliable strategy to avoid nitrite oxidation should be defined in order to maintain the process stability and to obtain the desired effluent quality. If not, the application of a post-denitrification step should be necessary.
Anaerobic digestion (AD) is commonly used for the stabilization of agro-food wastes and recovery of energy as methane. Since AD removes organic C but not nutrients (N and P), additional processes to ...remove them are usually applied to meet the stringent effluent criteria. However, in the past years, there was a shift from the removal to the recovery of nutrients as a result of increasing concerns regarding limited natural resources and the importance given to the sustainable treatment technologies. Recovering N and P from anaerobically pretreated agro-food wastes as easily transportable and marketable products has gained increasing importance to meet both regulatory requirements and increase revenue. For this reason, this review paper gives a critical comparison of the available and emerging technologies for N and P recovery from AD residues.
Aerobic granular sludge is presented as an alternative technology to conventional activated sludge processes for the treatment of low-strength wastewaters. Results obtained with granular aerobic ...reactors at laboratory scale are promising but, there are few studies carried out at pilot scale. Therefore, more information about the stability of granules and their performance at larger scale is needed to establish if aerobic granulation could be a feasible treatment. With this aim, a 100L granular sequencing batch reactor (GSBR) operating at high loading rate and treating low-strength wastewater for simultaneous carbon, nitrogen and phosphorus removal was operated for 11months. Mature granules prevailed in the GSBR during a period of 5months (from days 150 to 330), with a SVI30 of 13±6mLg−1 TSS, a granule density around 114±5g TSS L−1 and an average particle size of 2.4mm. The biological nitrogen removal with mature granules was mainly performed via nitrite, probably due to the large granule size achieved. Nitrification efficiency was higher than 75% and occurred simultaneously with denitrification during the aerobic phase of the GSBR. A progressive accumulation of P-salts (probably apatite), was found from days 150 to 300, which could enhance the destabilization of granules at the end of the experimental period.
► A GSBR at pilot scale was stably operated during almost a year. ► The GSBR removed C, N and P from a low-strength wastewater at high loading rates. ► Long term operation with EBPR leads to the accumulation of inorganic particles in the granules. ► BNR was via nitrite, and simultaneous nitrification and denitrification was achieved.
Retrofitting wastewater treatment plants with continuous aerobic granular sludge reactors is a promising alternative to enhance treatment capacities and reduce footprint. This study investigates the ...main variables influencing granulation and microbial dynamics in two reactor configurations (25 L): stirred tanks in series (R1) and a plug-flow-like system (R2). Granule formation was achieved by increasing the organic loading rate (OLR) from 0.7 to 4.1 kg COD/(m3·d) and the up-flow velocity in the biomass selector from 1.4 to 6.9 m/h. However, irreversible granule destabilization occurred at day 68 for R1 and day 108 for R2. Principal component analysis and examination of food-to-microorganisms (F/M) ratio medians identified the F/M ratio as the primary variable associated with instability. Microbial analysis revealed that a high F/M ratio induced significant increases in the abundance of specific genera such as Arcobacter, Cloacibacterium, Rikenella, Aquaspirillum and Sphaerotillus, whose overgrowth may negatively impact granule stability. Based on these findings, maximum F/M ratio thresholds were obtained to establish operational conditions allowing the maintenance of stable aerobic granules on continuous flow reactor configurations.
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•Different configurations of continuous flow systems successfully form granules.•Granulation is affected by organic loading rate, up-flow velocity, and F/M ratio.•Growth of specific bacterial genera is associated with granule destabilization.•Threshold F/M ratios were determined to maintain granules stability.
Nitrification and sulfur-based autotrophic denitrification processes can be used to remove ammonia from wastewater in an economical way. However, under certain operational conditions, these processes ...accumulate intermediate compounds, such as elemental sulphur, nitrite, and nitrous oxide, that are noxious for the environment. In order to predict the generation of these compounds, an analysis based on the Gibbs free energy of the possible reactions and on the oxidative capacity of the bulk liquid was done on case study systems. Results indicate that the Gibbs free energy is not a useful parameter to predict the generation of intermediate products in nitrification and autotrophic denitrification processes. Nevertheless, we show that the specific productions of nitrous oxide during nitrification, and of elemental sulphur and nitrite during autotrophic denitrification, are well related to the oxidative capacity of the bulk liquid.
Aerobic granular sequencing batch reactors (SBRs) are usually inoculated with activated sludge which implies sometimes long start-up periods and high solids concentrations in the effluent due to the ...initial wash-out of the inoculum. In this work, the use of aerobic mature granules as inoculum in order to improve the start-up period was tested, but no clear differences were observed compared to a reactor inoculated with activated sludge. The effect of the aeration rate on both physical properties of granules and reactor performance was also studied in a stable aerobic granular SBR. The increase of the aeration flow rate caused the decrease of the average diameter of the granules. This fact enhanced the COD and ammonia consumption rates due to the increase of the DO level and the aerobic fraction of the biomass. However, it provoked a loss of the nitrogen removal efficiency due to the worsening of the denitrification capacity as a consequence of a higher aerobic fraction.
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