Cheese manufacturing wastewater treatment by combined physicochemical processes for reuse and fertilizer production.

Making cheese manufacturing environmentally sustainable is a major concern in the integrated management of this industrial sector. This concern is mainly due to the environmental impact of the discharge of its wastewaters, carrying heavy loads of salinity, nutrients, organic matter, solids and oils and fats. These discharges must meet increasingly stringent quality requirements. Some physicochemical (e.g. coagulation-flocculation, precipitation, oxidation) and biological (e.g. aerobic and anaerobic bioreactors and wetlands) treatments have been studied to address this problem. However, these treatments involve costs that some producers cannot sustain, face difficulties with biological reactor operational stability and often fail to consistently produce effluents compatible with discharge standards. In this context, aiming at the design of a simple and economical treatment method, several precipitation processes were tested using a fixed dosage of CaCO3 (75 g/L), combined with different dosages of FeCl3, FeSO4 or Ca(OH)2. The goal of the treatment was to produce a supernatant that would be evaluated as to its suitability for discharge into natural water courses or municipal treatment systems, or for reuse applications. The generated sludge would be evaluated for possible agricultural valorization. Through the measurement of the relevant supernatant quality parameters and using statistical analysis, it was possible to choose the best dosages for each of the tested coagulants (1.0, 1.0 and 0.6 g/L for FeCl3, FeSO4 and Ca(OH)2, respectively). Among these, the most efficient treatment was obtained with CaCO3 75 g/L + FeSO4 1.0 g/L. For this best-case scenario, the treatment led to removal yield values of 55.1% for chemical oxygen demand (COD), 92.0% for total phosphorus, 95.7% for turbidity, 59.1% for total phenols, 94.3% for nitrates, 71.0% for nitrites, 51.0% for total solids (TS) and 97.2% for oils and fats. The treatment did not produce an effluent supernatant with adequate quality for direct discharge into water courses, serving however as an efficient pretreatment for agricultural reuse. All the sludges generated in these treatments showed good potential for agricultural valorization due to their high nutrient content, along with pH and conductivity values within the acceptable ranges for soil application. Thus, this work contributes for a better integration of the cheese manufacturing industry in the overall aims of water and nutrient resources recovery in rural, agricultural areas.

Combining biotechnology with circular bioeconomy: From poultry, swine, cattle, brewery, dairy and urban wastewaters to biohydrogen.

The ability of microalgae to grow in nutrient-rich environments and to accumulate nutrients from wastewaters (WW) makes them attractive for the sustainable and low-cost treatment of WW. The valuable biomass produced can be further used for the generation of bioenergy, animal feed, fertilizers, and biopolymers, among others. In this study, Scenedesmus obliquus was able to remove nutrients from different wastewaters (poultry, swine and cattle breeding, brewery and dairy industries, and urban) with removal ranges of 95-100% for nitrogen, 63-99% for phosphorus and 48-70% for chemical oxygen demand. The biomass productivity using wastewaters was higher (except for poultry) than in synthetic medium (Bristol), the highest value being obtained in brewery wastewater (1025 mg/(L.day) of freeze-dried biomass). The produced biomass contained 31-53% of proteins, 12-36% of sugars and 8-23% of lipids, regardless of the type of wastewater. The potential of the produced Scenedesmus obliquus biomass for the generation of BioH2 through batch dark fermentation processes with Enterobacter aerogenes was evaluated. The obtained yields ranged, in mL H2/g Volatile Solids (VS), from 50.1 for biomass from anaerobically digested cattle WW to 390 for swine WW, whereas the yield with biomass cultivated in Bristol medium was 57.6 mL H2/gVS.

Stability of aerobic granules during long-term bioreactor operation.

Aerobic granular sludge technology has been extensively studied over the past 20 years and is regarded as the upcoming new standard for biological treatment of domestic and industrial wastewaters. Aerobic granules (AG) are dense, compact, self-immobilized microbial aggregates that allow better sludge-water separation and thereby higher biomass concentrations in the bioreactor than conventional activated sludge aggregates. This brings potential practical advantages in terms of investment cost, energy consumption and footprint. Yet, despite the relevant advances regarding the process of AG formation, instability of AG during long-term operation is still seen as a major barrier for a broad practical application of this technology. This paper presents an up-to-date review of the literature focusing on AG stability, aiming to contribute to the identification of key factors for promoting long-term stability of AG and to a better understanding of the underlying mechanisms. Operational conditions leading to AG disintegration are described, including high organic loads, particulate substrates in the influent, toxic feed components, aerobic feeding and too short famine periods. These operational and influent wastewater composition conditions were shown to influence the micro-environment of AG, consequently affecting their stability. Granule stability is generally favored by the presence of a dense core, with microbial growth throughout the AG depth being a crucial intrinsic factor determining its structural integrity. Accordingly, possible practical solutions to improve granule long-term stability are described, namely through the promotion of minimal substrate concentration gradients and control of microbial growth rates within AG, including anaerobic, plug-flow feeding and specific sludge removal strategies.

Calibration Transfer Between a Bench Scanning and a Submersible Diode Array Spectrophotometer for In Situ Wastewater Quality Monitoring in Sewer Systems.

Online monitoring programs based on spectroscopy have a high application potential for the detection of hazardous wastewater discharges in sewer systems. Wastewater hydraulics poses a challenge for in situ spectroscopy, especially when the system includes storm water connections leading to rapid changes in water depth, velocity, and in the water quality matrix. Thus, there is a need to optimize and fix the location of in situ instruments, limiting their availability for calibration. In this context, the development of calibration models on bench spectrophotometers to estimate wastewater quality parameters from spectra acquired with in situ instruments could be very useful. However, spectra contain information not only from the samples, but also from the spectrophotometer generally invalidating this approach. The use of calibration transfer methods is a promising solution to this problem. In this study, calibration models were developed using interval partial least squares (iPLS), for the estimation of total suspended solids (TSS) and chemical oxygen demand (COD) in sewage from Ultraviolet-visible spectra acquired in a bench scanning spectrophotometer. The feasibility of calibration transfer to a submersible, diode array equipment, to be subsequently operated in situ, was assessed using three procedures: slope and bias correction (SBC); single wavelength standardization (SWS) on mean spectra; and local centering (LC). The results showed that SBC was the most adequate for the available data, adding insignificant error to the base model estimates. Single wavelength standardization was a close second best, potentially more robust, and independent of the base iPLS model. Local centering was shown to be inadequate for the samples and instruments used.

Effect of an azo dye on the performance of an aerobic granular sludge sequencing batch reactor treating a simulated textile wastewater.

This study analyzed the effect of an azo dye (Acid Red 14) on the performance of an aerobic granular sludge (AGS) sequencing batch reactor (SBR) system operated with 6-h anaerobic-aerobic cycles for the treatment of a synthetic textile wastewater. In this sense, two SBRs inoculated with AGS from a domestic wastewater treatment plant were run in parallel, being one supplied with the dye and the other used as a dye-free control. The AGS successfully adapted to the new hydrodynamic conditions forming smaller, denser granules in both reactors, with optimal sludge volume index values of 19 and 17 mL g(-1) after 5-min and 30-min settling, respectively. As a result, high biomass concentration levels and sludge age values were registered, up to 13 gTSS L(-1) and 40 days, respectively, when deliberate biomass wastage was limited to the sampling needs. Stable dye removal yields above 90% were attained during the anaerobic reaction phase, confirmed by the formation of one of the aromatic amines arising from azo bond reduction. The control of the sludge retention time (SRT) to 15 days triggered a 30% reduction in the biodecolorization yield. However, the increase of the SRT values back to levels above 25 days reverted this effect and also promoted the complete bioconversion of the identified aromatic amine during the aerobic reaction phase. The dye and its breakdown products did not negatively affect the treatment performance, as organic load removal yields higher than 80% were attained in both reactors, up to 77% occurring in the anaerobic phase. These high anaerobic organic removal levels were correlated to an increase of Defluviicoccus-related glycogen accumulating organisms in the biomass. Also, the capacity of the system to deal with shocks of high dye concentration and organic load was successfully demonstrated. Granule breakup after long-term operation only occurred in the dye-free control SBR, suggesting that the azo dye plays an important role in improving granule stability. Fluorescence in situ hybridization (FISH) analysis confirmed the compact structure of the dye-fed granules, microbial activity being apparently maintained in the granule core, as opposed to the dye-free control. These findings support the potential application of the AGS technology for textile wastewater treatment.

Use of spectra in the visible and near-mid-ultraviolet range with principal component analysis and partial least squares processing for monitoring of suspended solids in municipal wastewater treatment plants.

The present work assesses the possibility of using spectrophotometry in the near-mid-ultraviolet and visible wavelength ranges (282-790 nm) for the direct monitoring of treatment performance in municipal wastewater treatment plants (WWTPs). Principal component analysis (PCA) was used to analyze spectral data from samples collected along three WWTP process lines with different primary and secondary treatment units. The clustering observed in PCA score plots was mainly attributed to the suspended solids fraction present in the wastewater and highlighted differences in solids quality between plants and along the treatment lines. Thus, satisfactory partial least squares (PLS) calibration models to estimate total suspended solids (TSS) values from the acquired spectra could only be established per plant. The PLS models were established using 1-2 factors, with root mean error of cross-validation and coefficient of determination values in the 50-86 mg TSS L(-1) and 82-95% ranges, respectively.

Behaviour of different anaerobic populations on the biodegradation of textile chemicals.

The anaerobic biodegradation of textile chemicals was evaluated with inocula grown under mesophilic (37+/-2 degrees C) or thermophilic (55+/-2 degrees C) conditions, on glucose (glucose-grown) or acetate (acetate-grown) as sole carbon sources. Wool dyebath chemicals (acetic acid, a liposomal surfactant, a synthetic amphoteric surfactant), single or as binary acetate-surfactant mixtures, were used as test carbon sources, in the presence or absence of Acid Orange 7 as model dye. First, the two mesophilic inocula (glucose- or acetate-grown) were compared relatively to lag-phase durations, specific biogas production rates, biogas yields and overall COD removal yields. In some runs, sulphide and/or the model dye were included, to test for inhibition effects. Then, the two glucose-grown inocula (mesophilic and thermophilic) were assessed in batch biodegradation tests with the same carbon feeds. The kinetics for substrate-COD and dye colour removal were described and quantified using a pseudo-first order model. The presence of dye had no effect on performance parameters for all substrates tested. Acetoclastic methanogens seemingly played an important role in biogas production from the liposomal additive, but less so from the synthetic surfactant. The association of acetate and surfactants apparently introduced mutual inhibitory effects on the rates of biogas production, substrate uptake and dye decolourisation.

Kinetic studies of reactive azo dye decolorization in anaerobic/aerobic sequencing batch reactors.

The decolorization kinetics of Remazol Brilliant Violet 5R (RBV-5R) and Remazol Black B (RB-B) (mono- and diazo reactive dyes, respectively) was investigated in the first 9 h (anaerobic phase) of a 24-h cycle anaerobic/aerobic sequencing batch reactor (SBR). Two distinct, successive decolorization periods were observed for both dyes, apparently due to different decolorization mechanisms. The apparent first-order rate constants were much lower for the second periods. First-order kinetics were apparently followed for both periods of RBV-5R but not for the first decolorization period of RB-B, possibly due to the occurrence of mass transfer limitations.

Mycobacterium sp., Rhodococcus erythropolis, and Pseudomonas putida behavior in the presence of organic solvents.

This work aimed at studying the behavior and tolerance of Mycobacterium sp. NRRL B-3805, Rhodococcus erythropolis DCL14 and Pseudomonas putida S12 cells in the presence of various concentrations of water miscible (ethanol, butanol, and dimethylformamide, up to 50% v/v) and water immiscible solvents (dodecane, bis(2-ethylhexyl) phthalate and toluene, up to 5% v/v). When incubated in the presence of these solvents, the cells were found to have lower tolerance to butanol and toluene than to the remaining solvents. Nevertheless, the concentrations of solvents endured by the tested strains show that they are quite solvent-tolerant, confirming their potential as biocatalysts in nonconventional systems. Microscopic observation of samples showed that the hydrophobic Mycobacterium sp. and R. erythropolis cells were able to aggregate to protect the population under stress conditions. Comparison of the results obtained at the single cell level by fluorescence microscopy and colony development on agar plates indicated that the primary effects of most solvents tested were on the cell membrane and replicating capability of the cells.