Primary filtration of municipal wastewater with sludge fermentation - Impacts on biological nutrient removal.

Primary filtration is a compact pre-treatment process for municipal wastewater, which can lead to high removal of total suspended solids (TSS) if polymer is added prior to filtration. Extensive carbon removal with rotating belt filter (RBF) can be combined with filter primary sludge fermentation at ambient temperature, in order to produce volatile fatty acids (VFAs) as carbon source for biological nutrient removal (BNR). This process was implemented at large pilot-scale and operated for more than a year. The results showed that the RBF efficiently removed particles >10 µm, and that the TSS removal had a strong linear correlation to the influent TSS concentration. Fermentation of the sludge at ambient temperature and five days retention time and addition of the fermentate to the wastewater could nearly double the VFA concentration in the wastewater by adding 31 ± 9 mg VFA-COD/L. Meanwhile, an increase of 2 mg/L of ammonium nitrogen, and 0.7 mg /L of phosphate phosphorus would be added to the wastewater with the fermentate. Adding the fermented sludge to the wastewater stream and removing the particles with RBF makes it possible to utilize nearly all the produced VFAs for BNR, and the feasibility of this configuration was shown at pilot-scale. According to simulations of subsequent BNR, the pre-treatment would lead to lower effluent total nitrogen concentrations. Alternatively, the required BNR volume could be reduced by 11-18 %. The estimated total biogas production was similar for pre-treatment with primary settler and RBF with fermentation. RBF without fermentation gave the most favourable energy balance, but did not reach the same low effluent value for total nitrogen as RBF with fermentation.

Case study of aerobic granular sludge and activated sludge-Energy usage, footprint, and nutrient removal.

This study demonstrates a comparison of energy usage, land footprint, and volumetric requirements of municipal wastewater treatment with aerobic granular sludge (AGS) and conventional activated sludge (CAS) at a full-scale wastewater treatment plant characterized by large fluctuations in nutrient loadings and temperature. The concentration of organic matter in the influent to the AGS was increased by means of hydrolysis and bypassing the pre-settler. Both treatment lines produced effluent concentrations below 5 mg BOD7 L-1 , 10 mg TN L-1 , and 1 mg TP L-1 , by enhanced biological nitrogen- and phosphorus removal. In this case study, the averages of volumetric energy usage over 1 year were 0.22 ± 0.08 and 0.26 ± 0.07 kWh m-3 for the AGS and CAS, respectively. A larger difference was observed for the energy usage per reduced population equivalents (P.E.), which was on average 0.19 ± 0.08 kWh P.E.-1 for the AGS and 0.30 ± 0.08 kWh P.E.-1 for the CAS. However, both processes had the potential for decreased energy usage. Over 1 year, both processes showed similar fluctuations in energy usage, related to variations in loading, temperature, and DO. The AGS had a lower specific area, 0.3 m2  m-3 d-1 , compared to 0.6 m2  m-3 d-1 of the CAS, and also a lower specific volume, 1.3 m3  m-3 d-1 compared to 2.0 m3  m-3 d-1 . This study confirms that AGS at full-scale can be compact and still have comparable energy usage as CAS. PRACTITIONER POINTS: Full-scale case study comparison of aerobic granular sludge (AGS) and conventional activated sludge (CAS), operated in parallel. AGS had 50 % lower footprint compared to CAS. Energy usage was lower in the AGS, but both processes had potential to improve the energy usage efficiency. Both processes showed low average effluent concentrations.

Seasonal variations in acidogenic fermentation of filter primary sludge.

Primary treatment of municipal wastewater by rotating belt filtration followed by hydrolysis and acidogenic fermentation of the filter primary sludge (FPS) at ambient temperature was studied at pilot-scale during one year. The seasonal variations of volatile fatty acids (VFAs), nutrient release and soluble COD production as well as microbial community assembly were assessed, leading to novel findings for fermentation at ambient temperature. The reproducibility of VFA production performance was first established by operating the two fermentation reactors under the same conditions, showing similar results regarding VFA production and microbial community structure. One year of operation at 5 d retention time (RT) and 16-29 °C resulted in an average VFA yield of 180±35 mg COD/g VSin and soluble COD yield of 242±40 mg COD/g VSin. The VFA formation was temperature-dependent, with Ï´=1.033±0.005 ( [Formula: see text] . The seasonal variations of the acetic and propionic acid productions were pronounced, whereas the productions of VFAs with longer chains were more stable regardless of temperature. The community structure of the reactor microbiomes was also clearly affected by season and temperature and linked with the production spectrum of VFAs. The ammonium and phosphate releases were stable during the year, leading to a decrease in ratios of soluble COD to NH4+-N and PO43--P during winter. The soluble COD yield was 11% and 27% higher at 5 d RT compared to 3 and 2 d RT respectively, but the corresponding volumetric productivities were lower. The dissimilarities between microbiomes in influent FPS and fermenters were significant even at a short RT of 2 d, and increased with longer RT of 3 and 5 d, primarily caused by selection of bacteria within Bacteroidota in the fermentation reactors.

Bacteriophages in Biological Wastewater Treatment Systems: Occurrence, Characterization, and Function.

Phage bacteria interactions can affect structure, dynamics, and function of microbial communities. In the context of biological wastewater treatment (BWT), the presence of phages can alter the efficiency of the treatment process and influence the quality of the treated effluent. The active role of phages in BWT has been demonstrated, but many questions remain unanswered regarding the diversity of phages in these engineered environments, the dynamics of infection, the determination of bacterial hosts, and the impact of their activity in full-scale processes. A deeper understanding of the phage ecology in BWT can lead the improvement of process monitoring and control, promote higher influent quality, and potentiate the use of phages as biocontrol agents. In this review, we highlight suitable methods for studying phages in wastewater adapted from other research fields, provide a critical overview on the current state of knowledge on the effect of phages on structure and function of BWT bacterial communities, and highlight gaps, opportunities, and priority questions to be addressed in future research.

Application of dissolved oxygen (DO) level control for polyhydroxyalkanoate (PHA) accumulation with concurrent nitrification in surplus municipal activated sludge.

Mixed microbial cultures are a viable means for polyhydroxyalkanoate (PHA) production, which can produce polymers of commercial quality with high yields. Various PHA co-polymer blends can be produced by surplus full-scale municipal activated sludge fed with fermented waste feedstocks. In biological nutrient removal, ammonia is converted to nitrate by ammonia and nitrite oxidizing bacteria (AOBs and NOBs) through nitrification and removed as nitrogen gas through denitrification. Activated sludge can be enriched with significant PHA storage potential alongside nitrogen removal by denitrifying heterotrophic and nitrifying autotrophic bacteria. The latter adds complexity and aeration demand during the aerobic side-stream PHA accumulation stage since fermented organic residuals often contain significant amounts of ammonia. In the present work, the influence of dissolved oxygen (DO) levels on both PHA accumulation and nitrification rates for a municipal activated sludge were evaluated. The objective was to identify potential for a DO control strategy for PHA accumulation, which would mitigate the unnecessary nitrification activity during PHA production. A much higher apparent Michaelis-Menten DO affinity for volatile fatty acid (VFA) consumption (KDO _VFA 0.1 ± 0.06 mg/L) was found as compared to nitrification (KDO _NH4 2.87 ± 1.31 mg/L). Consequently, with lower DO levels, PHA production was not limited by oxygen supply, while nitrogen was removed by simultaneous nitrification and denitrification processes. This study suggests a method for PHA accumulation using nitrifying activated sludge, while feeding ammonia-containing organic feedstocks by means of DO level control where: (1) NOB activity and growth are both mitigated, (2) nitrogen removal is facilitated, (3) alkalinity is controlled through simultaneous denitrification, and (4) energy demand for aeration is reduced.

A comparison of aerobic granular sludge with conventional and compact biological treatment technologies.

The aerobic granular sludge (AGS) technology is growing towards becoming a mature option for new municipal wastewater treatment plants and capacity extensions. A process based on AGS was compared to conventional activated sludge processes (with and without enhanced biological phosphorus removal), an integrated fixed-film activated sludge (IFAS) process and a membrane bioreactor (MBR) by estimating the land area demand (footprint), electricity demand and chemicals' consumption. The process alternatives compared included pre-settling, sludge digestion and necessary post-treatment to achieve effluent concentrations of 8 mg/L nitrogen and 0.2 mg/L phosphorus at 7°C. The alternative based on AGS was estimated to have a 40-50% smaller footprint and 23% less electricity requirement than conventional activated sludge. In relation to the other compact treatment options IFAS and MBR, the AGS process had an estimated electricity usage that was 35-70% lower. This suggests a favourable potential for processes based on AGS although more available experience of AGS operation and performance at full scale is desired.

Impact of activated sludge ozonation on filamentous bacteria viability and possible added benefits.

Ozone was applied to return activated sludge in full-scale to study how ozone impacts filamentous bacteria viability (Live/Dead®). Additionally, the ozonated sludges were subjected to anaerobic digestion trials and analysis of micropollutants (MPs). Ozone treatment (3-4.8 g O3/kg total suspended solids) improved the settling properties of the sludge by lowering the diluted sludge volume with 7-35%. Ozone inactivated filamentous bacteria outside the floc structures and the fraction of inactivated filaments increased with an increasing ozone dose. It was observed that ozone treatment may act selectively towards different types of filaments. With respect to the two dominating morphotypes present, Type 0041 filamentous bacteria were found to be more resistant to ozone attack than Microthrix parvicella. Thus, higher ozone doses may be required to mitigate sludge bulking caused by Type 0041 filaments. No effects could be discerned by ozone addition on neither the methane production of the sludge nor on the concentrations of MPs analysed for this study. The lack of effect on both methane production and micropollutant removal was deemed to be caused by insufficient ozone doses.

Consistent production of high quality PHA using activated sludge harvested from full scale municipal wastewater treatment - PHARIO.

Production of polyhydroxyalkanoate (PHA) biopolymers by mixed microbial cultures concurrent to wastewater treatment is a valorization route for residual organic material. This development has been at pilot scale since 2011 using industrial and municipal organic residuals. Previous experience was the basis for a PHA production demonstration project: PHARIO. PHARIO was centred on processing surplus activated sludge biomass from the Bath full-scale municipal wastewater treatment plant in the Netherlands to produce PHA. Full-scale surplus activated sludge was fed to a pilot facility to produce PHA rich biomass using fermented volatile fatty acid (VFA) rich liquors from industry or primary sludge sources. A PHA rich biomass with on average 0.41 gPHA/gVSS was obtained with reproducible thermal properties and high thermal stability. A routine kilogram scale production was established over 10 months and the polymer material properties and market potential were evaluated. Surplus full-scale activated sludge, over four seasons of operations, was a reliable raw material to consistently and predictably produce commercial quality grades of PHA. Polymer type and properties were systematic functions of the mean co-polymer content. The mean co-polymer content was predictably determined by the fermented feedstock composition. PHARIO polymers were estimated to have a significantly lower environmental impact compared to currently available (bio)plastics.

A process for polyhydroxyalkanoate (PHA) production from municipal wastewater treatment with biological carbon and nitrogen removal demonstrated at pilot-scale.

A process was developed for biological treatment of municipal wastewater for carbon and nitrogen removal while producing added-value polyhydroxyalkanoates (PHAs). The process comprised steps for pre-denitrification, nitrification and post-denitrification and included integrated fixed-film activated sludge (IFAS) with biofilm carrier media to support nitrification. In a pilot-scale demonstration (500-800L), wastewater treatment performance, in line with European standards, were achieved for total chemical oxygen demand (83% removal) and total nitrogen (80% removal) while producing a biomass that was able to accumulate up to 49% PHA of volatile suspended solids with acetic acid or fermented organic residues as substrates. Robust performance in wastewater treatment and enrichment of PHA-producing biomass was demonstrated under realistic conditions including influent variability during 225days of operation. The IFAS system was found to be advantageous since maintaining nitrification on the biofilm allowed for a relatively low (2days) solids retention time (SRT) for the suspended biomass in the bulk phase. Lower SRT has advantages in higher biomass yield and higher active fraction in the biomass which leads to higher PHA productivity and content. The outcomes show that production of added-value biopolymers may be readily integrated with carbon and nitrogen removal from municipal wastewater.

Integration of biopolymer production with process water treatment at a sugar factory.

The present investigation has focused on generating a surplus denitrifying biomass with high polyhydroxyalkanoate (PHA) producing potential while maintaining water treatment performance in biological nitrogen removal. The motivation for the study was to examine integration of PHA production into the water treatment and residuals management needs at the Suiker Unie sugar beet factory in Groningen, the Netherlands. At the factory, process waters are treated in nitrifying-denitrifying sequencing batch reactors (SBRs) to remove nitrogen found in condensate. Organic slippage (COD) in waters coming from beet washing is the substrate used for denitrification. The full-scale SBR was mimicked at laboratory scale. In two parallel laboratory scale SBRs, a mixed-culture biomass selection strategy of anoxic-feast and aerobic-famine was investigated using the condensate and wash water from Suiker Unie. One laboratory SBR was operated as conventional activated sludge with long solids retention time similar to the full-scale (SRT >16 days) while the other SBR was a hybrid biofilm-activated sludge (IFAS) process with short SRT (4-6 days) for the suspended solids. Both SBRs were found to produce biomass with augmented PHA production potential while sustaining process water treatment for carbon, nitrogen and phosphorus for the factory process waters. PHA producing potential in excess of 60 percent g-PHA/g-VSS was achieved with the lab scale surplus biomass. Surplus biomass of low (4-6 days) and high (>16 days) solids retention time yielded similar results in PHA accumulation potential. However, nitrification performance was found to be more robust for the IFAS SBR. Assessment of the SBR microbial ecology based on 16sDNA and selected PHA synthase genes at full-scale in comparison to biomass from the laboratory scale SBRs suggested that the full-scale process was enriched with a PHA storing microbial community. However, structure-function relationships based on RNA levels for the selected PHA synthases could not be established and, towards this ambition, it is speculated that a wider representation of PHA synthesases would need to be monitored. Additionally at the factory, beet tail press waters coming from the factory beet residuals management activities are available as a carbon source for PHA accumulation. At pilot scale, beet tail press waters were shown to provide a suitable carbon source for mixed culture PHA production in spite of otherwise being of relatively low organic strength (≤ 10 g-COD/L). A copolymer of 3-hydroxybutyrate with 3-hydroxyvalerate (PHBV with 15% HV on a molar basis) of high thermal stability and high weight average molecular mass (980 kDa) was produced from the beet tail press water. The mixed culture accumulation process sustained PHA storage with parallel biomass growth of PHA storing bacteria suggesting a strategy to further leverage the utilization of surplus functional biomass from biological treatment systems. Integration of PHA production into the existing factory water management by using surplus biomass from condensate water treatment and press waters from beet residuals processing was found to be a feasible strategy for biopolymer production.

Molecular weight and thermal properties of polyhydroxyalkanoates produced from fermented sugar molasses by open mixed cultures.

Polyhydroxyalkanoates (PHAs) produced from fermented molasses and synthetic feeds containing single volatile fatty acids (VFAs) by an open mixed culture enriched in glycogen accumulating organisms (GAOs) were characterized with regards to molecular weight and thermal properties. The polymer contained five types of monomers, namely 3-hydroxybutyrate, 3-hydroxy-2-methylbutyrate, 3-hydroxyvalerate, 3-hydroxy-2-methylvalerate and 3-hydroxyhexanoate in different ratios depending on the VFA composition of the substrate. Polymers produced from fermented molasses had weight average molecular weights (M(w)) in the range (3.5-4.3)x10(5)g/mol and polydispersity indexes (PDI) of 1.8-2.1 while polymers produced from synthetic VFAs had M(w) of (4.5-9.0)x10(5)g/mol and PDI of 1.7-3.9. Thermal properties such as glass transition temperature (-14 degrees C to 4.8 degrees C), melting temperature (89-174 degrees C) and melting enthalpy (0-82.1J/g) were controlled in broad ranges by the monomer composition. The decomposition temperatures of the polymers produced were between 277.2 degrees C and 294.9 degrees C, and independent of monomer composition and molecular weight.

Production of polyhydroxyalkanoates from fermented sugar cane molasses by a mixed culture enriched in glycogen accumulating organisms.

Batch production of polyhydroxyalkanoates (PHAs) under aerobic conditions by an open mixed culture enriched in glycogen accumulating organisms (GAOs) with fermented sugar cane molasses as substrate was studied. The produced polymers contained five types of monomers, namely 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), 3-hydroxy-2-methylbutyrate (3H2MB), 3-hydroxy-2-methylvalerate (3H2MV) and the medium chain length monomer 3-hydroxyhexanoate (3HHx). With fermented molasses as substrate, PHA was produced under concurrent consumption of stored glycogen with yields of 0.47-0.66 C-mol PHA per C-mol of total carbon substrate and with rates up to 0.65 C-mol/C-molX h. In order to investigate the role of glycogen during aerobic PHA accumulation in GAOs, synthetic single volatile fatty acids (VFAs) were used as substrates and it was found that the fate of glycogen was dependent on the type of VFA being consumed. Aerobic PHA accumulation occurred under concurrent glycogen consumption with acetate as substrate and under minor concurrent glycogen production with propionate as substrate. With butyrate and valerate as substrates, PHA accumulation occurred with the glycogen pool unaffected. The composition of the PHA was dependent on the VFA composition of the fermented molasses and was 56-70 mol-% 3HB, 13-43 mol-% 3HV, 1-23 mol-% 3HHx and 0-2 mol-% 3H2MB and 3H2MV. The high polymer yields and production rates suggest that enrichment of GAOs can be a fruitful strategy for mixed culture production of PHA from waste substrates.

The utilization of glycogen accumulating organisms for mixed culture production of polyhydroxyalkanoates.

Production of polyhydroxyalkanoates (PHAs) by an open mixed culture enriched in glycogen accumulating organisms (GAOs) under alternating anaerobic-aerobic conditions with acetate as carbon source was investigated. The culture exhibited a stable enrichment performance over the 450-day operating period with regards to phenotypic behavior and microbial community structure. Candidatus Competibacter phosphatis dominated the culture at between 54% and 70% of the bacterial biomass throughout the study, as determined by fluorescence in situ hybridization. In batch experiments under anaerobic conditions, PHA containing 3-hydroxybutyrate (3HB) and 27 mol-% 3-hydroxyvalerate (3HV) was accumulated up to 49% of cell dry weight utilizing the glycogen pool stored in the SBR cycle. Under aerobic and ammonia limited conditions, PHA comprising only 3HB was accumulated to 60% of cell dry weight. Glycogen was consumed during aerobic PHA accumulation as well as under anaerobic conditions, but with different stoichiometry. Under aerobic conditions 0.31 C-mol glycogen was consumed per consumed C-mol acetate compared to 0.99 under anaerobic conditions. Both the PHA biomass content and the specific PHA production rate obtained were similar to what is typically obtained using the more commonly applied aerobic dynamic feeding strategy.

Community structure evolution and enrichment of glycogen-accumulating organisms producing polyhydroxyalkanoates from fermented molasses.

An open mixed culture was enriched with glycogen-accumulating organisms (GAOs) by using a sequencing batch reactor and treating an agroindustrial waste (sugar cane molasses) under cyclic anaerobic-aerobic conditions. Over a 1-year operating period, the culture exhibited a very stable GAO phenotype with an average polyhydroxyalkanoate (PHA) content of 17% total suspended solids. However, the GAO microbial community evolved over the course of operation to a culture exhibiting unusual characteristics in producing PHAs comprised of short-chain-length monomers, namely, 3-hydroxybutyrate, 3-hydroxy-2-methylbutyrate, 3-hydroxyvalerate, and 3-hydroxy-2-methylvalerate, and also, up to 31 mol% of the medium-chain-length (MCL) monomer 3-hydroxyhexanoate (3HHx). Microbial community analysis by fluorescence in situ hybridization revealed a concurrent long-term drift in the GAO community balance, from mainly "Candidatus Competibacter phosphatis" to mainly Defluviicoccus vanus-related organisms. The production of 3HHx was confirmed by (13)C nuclear magnetic resonance (NMR) and appeared to be related to the increased presence of D. vanus-related GAOs. These results suggest a broadened spectrum of material, chemical, and mechanical properties that can be achieved for biopolymers produced by open mixed cultures from fermented waste. The increased spectrum of polymer properties brings a wider scope of potential applications.

Production of polyhydroxyalkanoates by glycogen accumulating organisms treating a paper mill wastewater.

A process for production of polyhydroxyalkanoates (PHA) by activated sludge treating a paper mill wastewater was investigated. The applied strategy was to select for glycogen accumulating organisms (GAOs) by alternating anaerobic/aerobic conditions. Acidogenic fermentation was used as pretreatment to convert various organic compounds to volatile fatty acids which are preferable substrates for PHA production. Enrichment resulted in a culture dominated by GAOs related to Defluviicoccus vanus (56%) and Candidatus Competibacter phosphatis (22%). Optimization of PHA accumulation by the enriched GAO culture was performed through batch experiments. Accumulation of PHA under anaerobic conditions was limited by the intracellular glycogen stored. Under aerobic conditions significant glycogen production (to 25% of sludge dry weight) was observed alongside PHA accumulation (to 22% of sludge dry weight). By applying a subsequent anaerobic period after an initial aerobic, the produced glycogen could be utilized for further PHA accumulation and by this strategy PHA content was increased to 42% of sludge dry weight. The PHA yield over the entire process was 0.10 kg per kg of influent COD treated which is similar to what has been achieved with a process applying feast/famine enrichment strategy with the same wastewater.

Chlorinated-solvent-free gas chromatographic analysis of biomass containing polyhydroxyalkanoates.

An extraction and derivatization method was developed for more environmentally friendly routine quantification of polyhydroxyalkanoates (PHAs) in activated sludge biomass by gas chromatography (GC). This method can be further applied to assess relative changes in biomass carbohydrate levels relating to, for example, glycogen or extracellular polysaccharides. Further, co-extracted principal membrane fatty acids are indicative of relative changes in active biomass. The protocol is attractive for routine assessment because it does not require any chlorinated solvents, which are still almost exclusively used today for PHA analysis by GC. Acidic alcoholysis of dried microbial biomass using 3:1 butanol to concentrated (37%) hydrochloric acid at 100 degrees C for 8 h will hydrolyse and derivatize microbial storage products and membrane lipids. Esters of the hydroxyalkanoates, carbohydrates converted to levulinic acid, and long chain microbial fatty acids are reliably extracted into hexane for gas chromatographic analysis and quantification. Calibration can be achieved with benzoic, 2-hydroxyvaleric, or 2-hydroxycaproic acids as the method reference standards.

Production of polyhydroxyalkanoates by activated sludge treating a paper mill wastewater.

Production of polyhydroxyalkanoates (PHAs) in activated sludge treating wastewater represents an economical and environmental promising alternative to pure culture fermentations. A process for production of PHA from a paper mill wastewater was examined at laboratory scale. The three stage process examined consisted of acidogenic fermentation to convert wastewater organic matter to volatile fatty acids (VFAs), an activated sludge system operating under feast/famine conditions to enrich for PHA producing organisms and accumulation of PHA in batch experiments. After fermentation of the wastewater, 74% of the soluble COD was present as VFA (acetate, propionate, butyrate and valerate) and the resulting PHA after batch accumulation consisted of 31-47 mol% hydroxybutyrate and 53-69 mol% hydroxyvalerate. The maximum PHA content achieved was 48% of the sludge dry weight and the three stage process exhibited a potential to produce 0.11 kg of PHA per kg of influent COD treated.