Sequencing Batch Biofilter Granular Reactor Research Articles

Treatment of secondary fiber papermaking wastewater with aerobic granular sludge cultured in a sequencing batch biofilter granular reactor

Abstract Secondary fiber papermaking wastewater (SPW) has received increasing interest because of its enormous discharge, typical high COD, and low biodegradability. The dense and compact structure of aerobic granular sludge (AGS) results in a high sludge concentration in the sequencing batch biofilter granular reactor (SBBGR), which provides superior conditions for the treatment of highly concentrated wastewater. This study constructed an SBBGR to treat SPW, investigated the changes in the species and structural characteristics of pollutants during wastewater treatment, and analyzed the dominant populations that can degrade pollutants in the SPW. The results showed that SBBGR had a good treatment effect on SPW and the removal rates of COD, TN, TP, SS, and color were 90.3 %, 81.9 %, 85.2 %, 73.1 %, and 75.1 % respectively with the influent organic load of 8.1 kg COD m−3 d−1, which was attributed to its outstanding biodegradability. The types and quantities of aromatic compounds in SPW were significantly reduced, according to the results of FTIR, UV–vis, and GC-MS. Microbial community analysis showed that the presence of Bacteroidetes, Proteobacteria, Macellibacteroides, Chlorobium, and Brachymonas in the SBBGR was responsible for the outstanding biodegradation of pollutants in the SPW. In summary, the treatment of SPW with SBBGR is extremely promising for applications.

Study on cultivation of aerobic granular sludge and its application in degrading lignin models in the sequencing batch biofilter granular reactor.

In this study, three sequencing batch biofilter granular reactors (SBBGRs) were employed to treat model lignin wastewater containing different lignin models (2,6-dimethoxyphenol, 4-methoxyphenol, and vanillin). After 40 days of cultivation, uniform-shaped aerobic granular sludge (AGS) was successfully developed through nutrient supplementation with synthetic wastewater. During the acclimation stage, the chemical oxygen demand (COD) reduction efficiencies of the three reactors showed a trend of initial decreasing (5-20%) and then recovering to a high reduction efficiency (exceeding 90%) in a short period of time. During the stable operation stage, all three reactors achieved COD reduction efficiencies exceeding 90%. These findings indicated the cultivated AGS's robust resistance to changes in lignin models in water. UV-Vis spectra analysis confirmed the effective degradation of the three lignin models. Microbiological analysis showed that Proteobacteria and Bacteroidetes were always the dominant phyla. At the genus level, while Acinetobacter (15.46%) dominated in the inoculation sludge, Kapabacteriales (7.93%), SBR1031 (11.77%), and Chlorobium (25.37%) were dominant in the three reactors (for 2,6-dimethoxyphenol, 4-methoxyphenol, and vanillin) after degradation, respectively. These findings demonstrate that AGS cultured with SBBGR effectively degrades lignin models, with different dominant strains observed for various lignin models.

Using sulfide as nitrite oxidizing bacteria inhibitor for the successful coupling of partial nitrification-anammox and sulfur autotrophic denitrification in one reactor

The partial nitrification-anammox (PNA) process, as a new “green” biological nitrogen removal technology, is completely autotrophic and has great economic and environmental benefits. However, the applied bottleneck of this process is the inability to inhibit nitrite oxidizing bacteria (NOB) activity and the low total nitrogen removal efficiency (TNRE) due to nitrate accumulation. In this study, the addition of sulfide was utilized to selectively screen NOB while promoting the sulfur autotrophic denitrification (SAD) process in one sequencing batch biofilter granular reactor. The results showed that when the influent concentration of NH4+-N and S2− were 184.6 ± 4.4 mg/L and 153.9 ± 3.1 mg/L, the average TNRE reached 89.6 ± 3.6 %. At this stage, aerobic ammonia oxidizing bacteria (AOB) and anaerobic ammonium oxidation bacteria (AnAOB) showed good activities (specific oxygen uptake rate of AOB and specific anammox activity could reach to 0.09 ± 0.00 mg O2/g SS/h and 0.47 ± 0.06 mg TN/g SS/h, respectively), while NOB activity was significantly suppressed by sulfide, with specific oxygen uptake rate of 0.003 ± 0.00 mg O2/g SS/h, which further demonstrating the feasibility and long-term application of this sustainable and efficient process. Anammox was the predominant nitrogen removal pathway contributing approximately 89.0 % of nitrogen removal. Typical AOB (Nitrosomonas), AnAOB (Candidatus Kuenenia), and SAD bacteria (Thiobacillus, Pseudoxanthomonas, and Limobacter) coexisted in the PNA-SAD system. The syntrophic interactions among sulfur-oxidizing, sulfate-reducing, and anammox bacterial populations of this system were revealed by PICRUST2 and network analysis. Sulfides were most likely oxidized to biologically produced elemental sulfur first and then converted to sulfate via the Sox system. Our study provided a new reaction scheme and theoretical reference for efficient nitrogen and sulfur removal in a single reactor.

Study on the formation process and mechanism of aerobic granular sludge in the sequencing batch biofilter granular reactor.

Sequencing batch biofilter granular reactor (SBBGR) is a promising wastewater treatment technology owing to its low sludge yield and good toxicity tolerance. However, little attention has been paid to the formation process and mechanism of aerobic granular sludge in SBBGR. This study systematically investigated the formation process and mechanism of aerobic granular sludge in an SBBGR to provide a theoretical basis for optimizing the culture of aerobic granular sludge. Aerobic granular sludge with good performance was successfully cultivated after 40 days of incubation using synthetic wastewater as feed: the mixed liquid suspended solids and mixed liquor volatile suspended solids increased from 3.85 and 1.85 g/L to 31.38 and 24.74 g/L respectively, and the COD, TN, and TP removal efficiencies were 91.21%, 84.99%, and 58.14%, respectively. The experimental results showed that Amoebacteria and Bacteroides played an important role in the formation of aerobic granular sludge, filamentous bacteria acted as a three-dimensional skeleton surrounded by filling bacilli and rod-shaped bacteria, and proteins played a dominant role in promoting granulation during the culture process.

SBBGR technology for reducing waste sludge production during plastic recycling process: Assessment of potential increase in sludge hazardousness

Sludge production in the wastewater treatment sector is consistently increasing and represents a critical environmental and economic issue. This study evaluated an unconventional approach for treating wastewater generated from the cleaning of non-hazardous plastic solid waste during the plastic recycling process. The proposed scheme was based on sequencing batch biofilter granular reactor (SBBGR) technology, which was compared with the activated sludge-based treatment currently in operation. These treatment technologies were compared regarding sludge quality, specific sludge production, and effluent quality to highlight whether the reduced sludge production shown by SBBGR corresponded to an increase in the concentration of hazardous compounds in the sludge. The SBBGR technology showed remarkable removal efficiencies (TSS, VSS, and NH3 > 99 %; COD >90 %; TN and TP > 80 %) and a sludge production six-fold lower than the conventional plant (in terms of kgTSS/kg CODremoved). Biomass from the SBBGR did not show a significant accumulation of organic micropollutants (i.e., long-chain hydrocarbons, chlorinated pesticides and chlorobenzenes, PCB, PCDD/F, PAH, chlorinated and brominated aliphatic compounds, and aromatic solvents), whereas a certain accumulation of heavy metals was observed. Furthermore, an initial attempt to compare the operating costs of the two treatment approaches revealed that the SBBGR technology would provide 38 % savings.

Integrating biodegradation and ozone-catalysed oxidation for treatment and reuse of biomass gasification wastewater

Syngas purification via wet-scrubbing processes generates a relevant amount of wastewater, which requires proper treatments before its disposal or reuse. Integrating chemical with cost-saving biological approaches represent a valuable alternative to traditional chemical-physical treatments. This study investigated the effectiveness of the BIO&CHEM treatment scheme for the treatment and reuse of wastewater collected from a wet-scrubber unit (chemical oxygen demand, COD = 2600 mg/L) containing several hazardous pollutants such as phenol (110 mg/L) and xylene (64 mg/L). The BIO&CHEM system included a sequencing batch biofilter granular reactor (SBBGR) and an ozonation unit that were operated at different hydraulic retention times (HRTs, from 5 to 1 day) and transferred ozone doses (TODs, 400, 280 and 250 mg/Linf), respectively. When a 4 d-HRT was selected, biologically treated wastewater was characterized by a COD of 140 mg/L and its toxicity on Daphnia magna was decreased from 100% to 5%. The integration between the biological SBBGR-based treatment (HRT = 1.5 d) and the ozonation (TOD = 280 mg/Linf) lowered effluent COD to 33 mg/L and erased toxicity on Daphnia magna. This operating condition resulted the most sustainable enabling multiple wastewater reuse and a significant reduction of plant size comparing with the biological treatment. Furthermore, the investigated aromatic and polyaromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs; including benzene, toluene, xylene and phenol) were completely removed. The analysis of the reactor biomass, performed at the end of the experimental trial, excluded also their mere accumulation within the reactor due to absorption or adsorption on the sludge.

Treating and reusing wastewater generated by the washing operations in the non-hazardous plastic solid waste recycling process: Advanced method vs. conventional method

The effectiveness of an advanced treatment of wastewater generated by non-hazardous plastic solid waste (PSW) washing, based on the Sequencing Batch Biofilter Granular Reactor (SBBGR), was assessed in terms of gross parameters, removal efficiencies and sludge production. The proposed treatment was also compared with the conventional treatment, which was based on primary and secondary treatments, using the activated sludge process, performed by Recuperi Pugliesi, a leading company in the plastic recycling industry located in Bari, Italy. The company produces low-density polyethylene (LDPE) regenerated granules from PSW used in agricultural and floricultural greenhouse activities and industrial packaging after a washing stage in the aqueous phase. The latter generates large volumes of wastewater, the conventional treatment of which is characterised by large quantities of sludge and the associated disposal problems. Under steady-state conditions, the SBBGR provided impressive removal efficiencies regarding the main gross parameters (over 90% for COD and TKN, over 99% for BOD5, TSS, VSS and NH3, and over 80% for TN) with a statistically better effluent quality than that of the conventional treatment. The SBBGR effluent quality was modelled in terms of washing water characteristics by using generalized additive models (GAMs). The SBBGR treatment was characterised by a specific sludge production five times lower than that of the conventional treatment (0.21 kg TSS vs. 1.0 kg TSS per m3 of wastewater treated). Compared with the conventional treatment, the proposed process showed a five-fold reduction in the cost of sludge disposal, which saved 50% of the operating cost.

Thermal energy recovery from a sequencing batch biofilter granular reactor (SBBGR) on a pilot scale: Evaluation of the effects of energy extraction on the depuration process, process effectiveness, and results scalability

Urban wastewater is a valuable source of clean energy available for both building conditioning and hot sanitary water production, thus reducing primary energy demand and greenhouse gas emissions. In the present study, the integration of a highly efficient solar-assisted fully off-the-grid water-source heat pump (SHP) with a sequencing batch biofilter granular reactor (SBBGR) is tested on a pilot scale for recovering and reusing thermal energy generated during the depuration process. The prototype was designed to simulate wastewater production (240 L/d), domestic hot water (DHW) (152 L/d at 40 °C), and space heating (20–25 °C) energy demand for a one-person equivalent. Three set temperatures for heat extraction from the SBBGR were tested: 20, 14, and 10 °C. Heat extraction had limited effects on the average SBBGR performances. The SBBGR ensured a removal efficiency close to 90% for total suspended solids (TSS), chemical oxygen demand (COD), and ammonia, whereas a decrease in total nitrogen (TN) removal efficiency, namely from 75% to 71%, was observed with the operating temperature decrease. Energy recovery data suggested that the energy extracted from the SBBGR might cover the energy demand for DHW production or space heating from April to October. Thus, the collected energy data was modeled with the following purposes: highlighting the key parameters for optimizing energy recovery, quantifying the share of recoverable energy derived the microbial metabolism, and supporting or rejecting the scalability of the results. The model outcomes confirmed that the temperature difference between the sewage and heat extraction set point temperatures was the key parameter for energy recovery and succeeded in estimating the contribution of microbial metabolisms (i.e. about 3.2 kWh/m3•d). However, the estimation of the full-scale recoverable energy was partially biased by the impact of the environmental conditions on the pilot.

Aerobic granular-based technology for water and energy recovery from municipal wastewater

In the present study, the possibility of recovering both thermal energy and water for agricultural purposes from sewage is evaluated. A treatment plant, based on a sequencing batch biofilter granular reactor (SBBGR) followed by sand filtration and coupled with a solar wastewater source heat pump, was operated from September to November 2018 at a set-point temperature of 14 °C to verify the stability of heat recovery efficiency and the suitability of plant effluent to be reused for irrigation. Heat recovery did not influence the SBBGR treatment and disinfection efficiency, which removed about 90% of suspended solids, chemical and biochemical oxygen demand and ammonia, as well as 70% of total nitrogen, 3 log10 units of Escherichia coli and more than 1 log10 unit of Clostridium perfringens. Furthermore, after sand filtration, water quality complied with the standards for agricultural reuse currently in force in several countries. Energy extracted from SBBGR was mainly influenced by environmental conditions, affecting wastewater temperature, and also by wastewater composition, affecting the energy release due to bacterial metabolic activity for carbon and nitrogen removal. Notably, no evident deterioration of energy extraction efficiency from the SBBGR was observed, suggesting negligible fouling phenomena on the submerged thermal exchanger.

Prospective environmental and economic assessment of solar-assisted thermal energy recovery from wastewater through a sequencing batch biofilter granular reactor

The integration of an off-grid solar-assisted heat pump (SHP) and a sequencing batch biofilter granular reactor (SBBGR) for thermal energy recovery from wastewater was assessed by means of a prospective life cycle assessment (LCA) and life cycle costing (LCC), by theoretically scaling up a pilot installation in Bari, Italy, to a full-scale unit designed for 5000 person-equivalents. The LCA and LCC included all activities in the life cycle of the SHP and wastewater treatment plant (WWTP), namely construction, operation and end-of-life. The thermal energy produced by the SHP was assessed as supplying heating and cooling for an air-conditioning system, displacing a conventional air-source heat pump powered by electricity from the grid. This integrated system was compared to a reference situation where wastewater is treated in a conventional WWTP applying activated sludge with no thermal energy recovery system, showing clear environmental benefits in all impact indicators, such as a 42% reduction in greenhouse-gas emissions and a cost reduction of 53%. Several sensitivity analyses confirmed these findings, with the exception of the price rebound effect, which showed that the lower cost of the integrated system could lead to overturning the environmental benefits. As a limitation of the study, the distribution of the supplied air-conditioning to meet a demand off-site the WWTP premises, such as in residential buildings or hotels, was not included. Therefore, our results constitute only a preliminary positive outcome that should be validated in a real-life application.

Energy recovery capacity evaluation within innovative biological wastewater treatment process

Experimental study we present is a full-scale energy recovery system able to extract, by means of a water source heat pump, the leftover thermal bioenergy available in a Sequencing Batch Biofilter Granular Reactor (SBBGR) within the wastewater treatment process.Heat pump compressor engine was powered by a 5.1 kW Photovoltaic plant, thermal energy being recovered is accumulated by two phase change materials tanks (PCM) for heat and cold latent energy storage whose capacity is 0.3 and 0.5 m3 respectively, thermal energy excess was dissipated through evaporator and condenser devices.Thermal energy extracted from SBBGR ranged from 0 to 14.5 kWh as function of environmental temperature and temperature set point of SBBGR. It was largely affected by environmental temperature during radiation and no deterioration of SBBGR performances were recorded during energy extraction even at lowest temperature set point (i.e. 15 °C).Results obtained demonstrated that SBBGR technology, thanks to its particular process scheme, allows wastewater heat extraction within the treatment process operation, making it actually the only wastewater treatment system able to exchange energy at low temperature (15 °C) without prejudice to treatment performances and, at the same time, to operate a thermal regulation of the treatment reactors, integrating the optimization of thermo-dependent biological processes with energy recovery systems.

Comparison of different types of landfill leachate treatments by employment of nontarget screening to identify residual refractory organics and principal component analysis

Three different chemical oxidation processes were investigated in terms of their capability to degrade organic chemical components of real mature landfill-leachate in combination with biological treatment run in a Sequencing Batch Biofilter Granular Reactor (SBBGR). H2O2, H2O2 + UV and O3 were integrated with SBBGR and respective effluents were analyzed and compared with the effluent obtained from biological SBBGR treatment alone. In agreement with their respective oxidative power, conventional bulk parameters (residual COD, TOC, Ntot, TSS) determined from the resulting effluents evidenced the following efficacy ranking for degradation: SBBGR/O3 > SBBGR/UV + H2O2 > SBBGR/H2O2 > SBBGR. A more detailed characterization of the organic compounds was subsequently carried out for the four treated streams. For this, effluents were first subjected to a sample preparation step, allowing for a classification in terms of acidic, basic, strongly acidic and strongly basic compounds, and finally to analysis by liquid chromatography/high resolution mass spectrometry (LC/HR-MS). This classification, combined with further data post-processing (non-target screening, Venn Diagram, tri-dimensional plot and Principal Component Analysis), evidenced that the SBBGR/H2O2 process is comparable to the pure biological oxidation. In contrast, SBBGR/O3 and SBBGR/UV + H2O2 not only resulted in a very different residual composition as compared to SBBGR and SBBGR/H2O2, but also differ significantly from each other. In fact, and despite of the SBBGR/O3 being the most efficient process, this treatment remained chemically more similar to SBBGR/H2O2 than to SBBGR/UV + H2O2. This finding may be attributable to different mechanism of degradation involved with the use of UV radiation. Apart from these treatment differences, a series of recalcitrant compounds was determined in all of the four treatments and partly identified as hetero-poly-aromatic species (humic acids-like species).

Realization of microbial community stratification for single-stage nitrogen removal in a sequencing batch biofilter granular reactor

A permanent microbial stratified nitrogen removal system coupling anammox with partial nitrification (SNAP) in a sequencing batch biofilter granular reactor (SBBGR) was successfully constructed for the treatment of ammonia-rich wastewater. With a nitrogen loading rate of 0.1kgNm−3·d−1, the maximal ammonia and total nitrogen removal efficiencies could reach up to 96.08% and 84.86% on day 108, respectively. The pH, DO profiles revealed a switch of functional species (AOB and anammox) at a typical intermittent aeration cycle. qPCR and high throughput analyses certified a stable spatial microbial stratified community structure. Although, anammox preferred strict anaerobic environment while AOB needed oxygen, a special stratified community structure contributed to conquer this obstacle. Moreover, Bacteroidet, Chlorobi, OD1, Planctomycetes, and Proteobacteria were the dominant species in the SBBGR. Although we have predicted the possible pathways of nitrogen transformation, further studies are needed to validate the pathways in enzymology.

Upgrading small wastewater treatment plants with the sequencing batch biofilter granular reactor technology: Techno-economic and environmental assessment

This paper is aimed at evaluating, from a techno-economic and environmental point of view, the performance of an existing wastewater treatment plant in which the traditional biological section is upgraded with an innovative Sequencing Batch Biofilter Granular Reactor. Two scenarios were simulated in order to model and assess the performances of conventional (CAS, Conventional Activated Sludge) and innovative solutions, based on mass balances, techno-economic evaluation and environmental assessment. The results showed that converting the activated sludge process into an SBBGR allows to achieve a drastic reduction in sludge production (up to 75% as volatile suspended solids). Furthermore, the secondary sedimentation and sludge stabilization units can be dismissed, reducing the area requirement (up to 50%). The technical assessment is mainly positive, with the electric energy consumption being the only critical item. The higher energy demand of the upgraded plant (about 25% more than the conventional treatment) is mainly associated with the recycle flow in the SBBGR system. Although the economic sustainability of the upgraded plant depends on local conditions, it can be considered to be likely favourable: sludge disposal and materials & reagents costs, together with the investment for plant reconstruction are those items that should be carefully evaluated before upgrading the CAS plant with SBBGR technology. The environmental assessment shows also mostly positive results, although it points to the increased phosphorus concentration in the effluent as a potentially critical issue and it highlights the electricity use and the increased nitrous oxide generation as other matters that need to be carefully checked in real case application.

Antibiotic resistance genes fate and removal by a technological treatment solution for water reuse in agriculture

In order to mitigate the potential effects on the human health which are associated to the use of treated wastewater in agriculture, antibiotic resistance genes (ARGs) are required to be carefully monitored in wastewater reuse processes and their spread should be prevented by the development of efficient treatment technologies. Objective of this study was the assessment of ARGs reduction efficiencies of a novel technological treatment solution for agricultural reuse of municipal wastewaters. The proposed solution comprises an advanced biological treatment (Sequencing Batch Biofilter Granular Reactor, SBBGR), analysed both al laboratory and pilot scale, followed by sand filtration and two different disinfection final stages: ultraviolet light (UV) radiation and peracetic acid (PAA) treatments. By Polymerase Chain Reaction (PCR), the presence of 9 ARGs (ampC, mecA, ermB, sul1, sul2, tetA, tetO, tetW, vanA) were analysed and by quantitative PCR (qPCR) their removal was determined. The obtained results were compared to the reduction of total bacteria (16S rDNA gene) and of a faecal contamination indicator (Escherichia coli uidA gene). Only four of the analysed genes (ermB, sul1, sul2, tetA) were detected in raw wastewater and their abundance was estimated to be 3.4±0.7 x104 - 9.6±0.5 x109 and 1.0±0.3 x103 to 3.0±0.1 x107 gene copies/mL in raw and treated wastewaters, respectively. The results show that SBBGR technology is promising for the reduction of ARGs, achieving stable removal performance ranging from 1.0±0.4 to 2.8±0.7 log units, which is comparable to or higher than that reported for conventional activated sludge treatments. No reduction of the ARGs amount normalized to the total bacteria content (16S rDNA), was instead obtained, indicating that these genes are removed together with total bacteria and not specifically eliminated. Enhanced ARGs removal was obtained by sand filtration, while no reduction was achieved by both UV and PAA disinfection treatments tested in our study.

Gross parameters prediction of a granular-attached biomass reactor by means of multi-objective genetic-designed artificial neural networks: touristic pressure management case.

The Artificial Neural Networks by Multi-objective Genetic Algorithms (ANN-MOGA) model has been applied to gross parameters data of a Sequencing Batch Biofilter Granular Reactor (SBBGR) with the aim of providing an effective tool for predicting the fluctuations coming from touristic pressure. Six independent multivariate models, which were able to predict the dynamics of raw chemical oxygen demand (COD), soluble chemical oxygen demand (CODsol), total suspended solid (TSS), total nitrogen (TN), ammoniacal nitrogen (N-NH4 (+)) and total phosphorus (Ptot), were developed. The ANN-MOGA software application has shown to be suitable for addressing the SBBGR reactor modelling. The R (2) found are very good, with values equal to 0.94, 0.92, 0.88, 0.88, 0.98 and 0.91 for COD, CODsol, N-NH4 (+), TN, Ptot and TSS, respectively. A comparison was made between SBBGR and traditional activated sludge treatment plant modelling. The results showed the better performance of the ANN-MOGA application with respect to a wide selection of scientific literature cases.

Integration of an innovative biological treatment with physical or chemical disinfection for wastewater reuse

In the present paper, the effectiveness of a Sequencing Batch Biofilter Granular Reactor (SBBGR) and its integration with different disinfection strategies (UV irradiation, peracetic acid) for producing an effluent suitable for agricultural use was evaluated. The plant treated raw domestic sewage, and its performances were evaluated in terms of the removal efficiency of a wide group of physical, chemical and microbiological parameters. The SBBGR resulted really efficient in removing suspended solids, COD and nitrogen with an average effluent concentration of 5, 32 and 10mg/L, respectively. Lower removal efficiency was observed for phosphorus with an average concentration in the effluent of 3mg/L. Plant effluent was also characterized by an average electrical conductivity and sodium adsorption ratio of 680μS/cm and 2.9, respectively. Therefore, according to these gross parameters, the SBBGR effluent was conformed to the national standards required in Italy for agricultural reuse. Moreover, disinfection performances of the SBBGR was higher than that of conventional municipal wastewater treatment plants and met the quality criteria suggested by WHO (Escherichia coli<1000CFU/100mL) for agricultural reuse. In particular, the biological treatment by SBBGR removed 3.8±0.4logunits of Giardia lamblia, 2.8±0.8logunits of E. coli, 2.5±0.7logunits of total coliforms, 2.0±0.3logunits of Clostridium perfringens, 2.0±0.4logunits of Cryptosporidium parvum and 1.7±0.7logunits of Somatic coliphages. The investigated disinfection processes (UV and peracetic acid) resulted very effective for total coliforms, E. coli and somatic coliphages. In particular, a UV radiation and peracetic acid doses of 40mJ/cm2 and 1mg/L respectively reduced E. coli content in the effluent below the limit for agricultural reuse in Italy (10CFU/100mL). Conversely, they were both ineffective on C. perfringens spores.

A single-stage biological process for municipal sewage treatment in tourist areas

This pilot scale study aims to test the effectiveness of an innovative compact biological system (SBBGR – Sequencing Batch Biofilter Granular Reactor) for treating municipal wastewater in tourist areas characterised by intense seasonal water demand and wastewater discharge. The results obtained after a long term operation of 463 days have shown that the proposed system is able to assure average removal efficiencies higher than 90% for COD (chemical oxygen demand), total suspended solids and TKN (total Kjeldahl nitrogen) independently of the influent concentration values and organic loading, which ranged from 0.2 to 5.1 kgCOD/m3biofilter.d Furthermore, the plant showed a high degree of operation flexibility and stability in response to the organic load variations occurring in tourist areas. In fact, no significant deterioration in the plant's effluent quality was observed even during a sudden several-fold increase in organic loading. High nitrogen removal efficiencies (80%, on average) were also achieved thanks to the establishment of simultaneous nitrification-denitrification process favoured by the plant's high biomass concentration and operating conditions. Finally, the system was characterized by an excess sludge production much lower (60–80% lower) than that of conventional biological systems operating without a primary clarifier. An acceptable level of stabilization of excess sludge was also obtained so that a further stabilization process was no longer required.

Textile wastewater treatment: Aerobic granular sludge vs activated sludge systems

Textile effluents are characterised by high content of recalcitrant compounds and are often discharged (together with municipal wastewater to increase their treatability) into centralized wastewater treatment plants with a complex treatment scheme. This paper reports the results achieved adopting a granular sludge system (sequencing batch biofilter granular reactor – SBBGR) to treat mixed municipal-textile wastewater. Thanks to high average removals in SBBGR (82.1% chemical oxygen demand, 94.7% total suspended solids, 87.5% total Kjeldahl nitrogen, 77.1% surfactants), the Italian limits for discharge into a water receiver can be complied with the biological stage alone. The comparison with the performance of the centralized plant treating the same wastewater has showed that SBBGR system is able to produce an effluent of comparable quality with a simpler treatment scheme, a much lower hydraulic residence time (11 h against 30 h) and a lower sludge production.

On-site treatment of textile yarn dyeing effluents using an integrated biological–chemical oxidation process

This paper reports the results of the treatment of a yarn dyeing effluent using an integrated biological–chemical oxidation process. In particular, the biological unit was based on a sequencing batch biofilter granular sludge reactor (SBBGR), while the chemical treatment consisted of an ozonation step. Biological treatment alone was first performed as a reference for comparison. While biological treatment did not produce an effluent for direct discharge, the integrated process assured good treatment results, with satisfactory removal of chemical oxygen demand (up to 89.8 %), total nitrogen (up to 88.2 %), surfactants (up to 90.7 %) and colour (up to 99 %), with an ozone dose of 110 mg of ozone per litre of wastewater. Biomass characterization by fluorescence in situ hybridization has revealed that filamentous bacteria represented about 20 % of biomass (coherently with high sludge volume index values); thanks to its special design, SBBGR guaranteed, however, stable treatment performances and low effluent suspended solids concentrations, while conventional activated sludge systems suffer from sludge bulking and even treatment failure in such a condition. Furthermore, biomass characterization has evidenced the presence of a shortcut nitrification–denitrification process.