Municipal and industrial wastewater blending: Effect of the carbon/nitrogen ratio on microalgae productivity and biocompound accumulation.

Municipal wastewater (MW) and industrial wastewater from juice processing (IWJ) were blended in different proportions to assess the effect of the carbon/nitrogen (C/N) ratio on pollutant removal, microalgal biomass (MB) cultivation, and the accumulation of carotenoids and biocompounds. MB development was not observed in treatments with higher C/N ratios (>30.67). The wastewater mixture favored the removal of dissolved organic carbon (75.61 and 81.90%) and soluble chemical oxygen demand (66.78-88.85%), compared to the treatment composed exclusively of MW (T7). Treatments T3 and T6 (C/N ratio equal to 30.67 and 7.52, respectively) showed higher Chlorophyll-a concentrations, 1.47 and 1.54 times higher than T7 (C/N ratio 1.75). It was also observed that the C/N ratio of 30.67 favored the accumulation of carbohydrates and lipids (30.07% and 26.39%, respectively), while the C/N ratio of 7.52 improved protein accumulation (33.00%). The fatty acids C16:0, C18:1, C18:2, and C18:3 had the highest concentrations. Additionally, increasing the C/N ratio can be an efficient strategy to improve the production of fatty acids for biofuels, mainly due to the increased concentration of shorter-chain fatty acids (C16:0). These findings suggest that blending wastewater not only enhances treatment performance but also increases the accumulation of valuable carbohydrates and lipids in MB, and optimizes fatty acid production for biofuel applications. This research represents significant progress towards feasibility of using MB produced from wastewater.

Scenedesmus sp. strain SD07 cultivation in municipal wastewater for pollutant removal and production of lipid and exopolysaccharides.

In this study, an efficient microalgal strain SD07 was isolated from pond wastewater and identified as Scenedesmus sp. using the 18S rRNA gene sequence analysis. The strain SD07 was grown in a variety of concentrations (25-100%) of municipal wastewater. Scenedesmus sp. strain SD07 grown in 75% diluted wastewater produced a higher amount of biomass (1.93 ± 0.10 g L-1), and removal of chemical oxygen demand (COD), ammonium (NH4+), total nitrogen (TN) and total phosphate (TP) by 91.36%, 88.41%, 93.26% and 96.32%, respectively from wastewater. The harvested strain SD07 biomass has protein, carbohydrate and lipid contents of 35%, 20.4% and 33%, respectively. Fatty acid profiles revealed that the strain SD07 lipids mainly consist of palmitic acid (40.5%), palmitoleic acid (19%), linoleic acid (17%) and oleic acid (13.2%). Furthermore, strain SD07 cultured in 75% diluted wastewater produced 378 mg L-1 of exopolysaccharides (EPS). The EPS was utilized as a biostimulant in the cultivation of Solanum lycopersicum under salinity stress. In summary, these findings suggest that this Scenedesmus sp. strain SD07 can be employed for wastewater treatment as well as the production of valuable biomass, high-quality algal oil and EPS.

Enhanced biological wastewater treatment supplemented with anaerobic fermentation liquid of primary sludge.

The wastewater treatment performance in an inverted A2/O reactor supplemented with fermentation liquid of primary sludge was explored comparing to commercial carbon sources sodium acetate and glucose. Similar COD removal rate was observed with the effluent COD stably reaching the discharge standard for those 3 carbon sources. However, the fermentation liquid distributed more carbon source in the anaerobic zone. Fermentation liquid and sodium acetate tests achieved better nitrogen removal rate than glucose test. The fermentation liquid test showed the best biological phosphorus removal performance with the effluent phosphorus barely reaching the discharge standard. The microbial community characterization revealed that the fermentation liquid test was dominated by phylum Proteobacter in all the anoxic, anaerobic and aerobic zones. Denitrifying phosphorus accumulating organisms (PAOs) (i.e., genera Dechloromonas and unclassified_f__Rhodocyclaceae) were selectively enriched with high abundances (over 20%), which resulted in improved phosphorus removal efficiency. Moreover, the predicted abundances of enzymes involved in nitrogen and phosphorus removal were also enhanced by the fermentation liquid.

An anoxic-aerobic system combined with integrated vertical-flow constructed wetland to highly enhance simultaneous organics and nutrients removal in rural China.

The biggest problem in the treatment of rural domestic sewage is that the existing treatment projects require the big investment and the high operation and maintenance costs. To overcome this problem, cost-effective, low-consuming, resource-recovering and easy-maintenance technologies are urgently demanded. To this end, a novel anoxic-aerobic system combined with integrated vertical-flow constructed wetland (IVFCW) with source separation was proposed for treating rural sewage in this study. The anoxic-aerobic system contained the anoxic filter (ANF), two-stage waterwheel driving rotating biological contactors (ts-WDRBCs). Key parameters of ts-WDRBCs were identified to be 0.6 m drop height and 4 r/min rotational speed found on oxygenated clean water experiments. Then, the optimal operating parameters were determined to be 200% reflux ratio and 3 h hydraulic retention time of ts-WDRBCs. During the 80-day operation, 91.58 ± 1.86% COD, 96.17 ± 0.92% NH4+-N, 82.71 ± 3.92% TN and 92.28 ± 2.78% TP were removed under the optimal operating parameters. Compared with other treatment technologies, this combined bio-ecological system could achieve the higher simultaneous organics and nutrients removal. The effluent NO3--N/NH4+-N concentration ratio of ts-WDRBCs was 2.15 ± 0.54, which was proved to be beneficial for plants growth. The microbial communities coexisted in each section ensured the desired removal performance of combined bio-ecological system. Summarily, high performance together with low investment costs and cheap operation costs are characteristics that make this system a promising and competitive alternative for rural sewage treatment.

Environmentally relevant level of perfluorooctanoic acid affect the formation of aerobic granular sludge.

The growing increasing occurrence of perfluorooctanoic acid (PFOA) in wastewater has raised concerns about its potential impact on the environment. Nevertheless, the impact of PFOA at environmentally relevant level on the formation of aerobic granular sludge (AGS) is still a 'black box'. This study thus aims to fill this gap by comprehensive investigation of sludge properties, reactor performance and microbial community during the formation of AGS. It was found that 0.1 mg/L PFOA delayed the formation of AGS, causing relatively lower proportion of large size AGS at the end of operation process. Interestingly, the microorganisms contribute to the reactor's tolerance to PFOA by secreting more extracellular polymeric substances (EPS) to slow or block the entry of toxic substances into the cells. During the granule maturation period, the reactor nutrient removal especially chemical oxygen demand (COD) and total nitrogen (TN) were affected by PFOA, decreasing the corresponding removal efficiencies to ∼81.2% and ∼69.8%, respectively. Microbial analysis further revealed that PFOA decreased the abundances of Plasticicumulans, Thauera, Flavobacterium and Cytophagaceae_uncultured, but it has promoted Zoogloea and Betaproteobacteria_unclassified growth, which maintained the structures and functions of AGS. The above results revealed that the intrinsic mechanism of PFOA on the macroscopic representation of sludge granulation process was revealed, and it is expected to provide theoretical insights and practical support for direct adoption of municipal or industrial wastewater containing perfluorinated compounds to cultivate AGS.

Long term operation of a phototrophic biological nutrient removal system: Impact of CO2 concentration and light exposure on process performance.

The utilization of non-aerated microalgae-bacterial consortia for phototrophic biological nutrient removal (photo-BNR) has emerged as an alternative to conventional wastewater treatment. Photo-BNR systems are operated under transient illumination, with alternating dark-anaerobic, light-aerobic and dark-anoxic conditions. A deep understanding of the impact of operational parameters on the microbial consortium and respective nutrient removal efficiency in photo-BNR systems is required. The present study evaluates, for the first time, the long-term operation (260 days) of a photo-BNR system, fed with a COD:N:P mass ratio of 7.5:1:1, to understand its operational limitations. In particular, different CO2 concentrations in the feed (between 22 and 60 mg C/L of Na2CO3) and variations of light exposure (from 2.75 h to 5.25 h per 8 h cycle) were studied to determine their impact on key parameters, like oxygen production and availability of polyhydroxyalkanoates (PHA), on the performance of anoxic denitrification by polyphosphate accumulating organisms. Results indicate that oxygen production was more dependent on the light availability than on the CO2 concentration. Also, under operational conditions with a COD:Na2CO3 ratio of 8.3 mg COD/mg C and an average light availability of 5.4 ± 1.3 W h/g TSS, no internal PHA limitation was observed, and 95 ± 7%, 92 ± 5% and 86 ± 5% of removal efficiency could be achieved for phosphorus, ammonia and total nitrogen, respectively. 81 ± 1.7% of the ammonia was assimilated into the microbial biomass and 19 ± 1.7% was nitrified, showing that biomass assimilation was the main N removal mechanism taking place in the bioreactor. Overall, the photo-BNR system presented a good settling capacity (SVI ∼60 mL/g TSS) and was able to remove 38 ± 3.3 mg P/L and 33 ± 1.7 mg N/L, highlighting its potential for achieving wastewater treatment without the need of aeration.

Supplementation of micro-nutrients to growth media of microalgae-induced biomass and fatty acids composition for clean energy generation.

The presence of harmful heavy metals (HMs) in the aquatic environment can damage the environment and threaten human health. Traditional remediation techniques can have secondary impacts. Thus, more sustainable approaches must be developed. Microalgae have biological properties (such as high photosynthetic efficiency and growth), which are of great advantage in the HMs removal. In this study, the effect of various concentrations (2×, 4×, and 6×) of copper (Cu), cobalt (Co), and zinc (Zn) on microalgae (C. sorokiniana GEEL-01, P. kessleri GEEL-02, D. asymmetricus GEEL-05) was investigated. The microalgal growth kinetics, HMs removal, total nitrogen (TN), total phosphor (TP), and fatty acids (FAs) compositions were analyzed. The highest growth of 1.474 OD680nm and 1.348 OD680nm was obtained at 2× and 4×, respectively, for P. kessleri GEEL-02. P. kessleri GEEL-02 showed high removal efficiency of Cu, Co, and Zn (38.92-55.44%), (36.27-68.38%), and (32.94-51.71%), respectively. Fatty acids (FAs) analysis showed that saturated FAs in C. sorokiniana GEEL-01 and P. kessleri GEEL-02 increased at 2× and 4× concentrations while decreasing at 6×. For P. kessleri GEEL-02, the properties of biodiesel including the degree of unsaturation (UD) and cetane value (CN) increased at 2×, 4×, and 6× as compared to the control. Thus, this study demonstrated that the three microalgae (particularly P. kessleri GEEL-02) are more suitable for nutrient and HMs removal coupled with biomass/biodiesel production.

Functional analysis of extracellular polymeric substances (EPS) during the granulation of aerobic sludge: Relationship among EPS, granulation and nutrients removal.

Extracellular polymeric substances (EPS) with high molecular weights, secreted from microorganisms, play a critical functional role in the aerobic granular sludge (AGS). To investigate the level and function of EPS during the granulation of aerobic sludge and in the mature AGS, a sequencing batch reactor (SBR) was operated for 70 days. Aerobic granules with an average diameter of 0.25 mm were obtained with reducing settling time of sludge. Simultaneous removals of COD, nitrogen and phosphorus by the mature AGS exceeded 90, 95 and 95%, respectively. The EPS content increased significantly to above 333 mg/g MLVSS during the initial stage, and after that, it stabilized at about 240 mg/g MLVSS as the mature AGS formed, higher than that of the seed sludge (212 mg/g MLVSS). The increased EPS contents showed a negative correlation with SVI values, while a strong positive relationship with the formation of the AGS. The protein/polysaccharide (PN/PS) ratio in the EPS increased from 1.42 to 4.17, and TP/MLSS increased to about 6%, with the formation of AGS. The proportion of extracellular-P increased with the increase of EPS, and then maintained stable at about 20%, indicating EPS promoted the removal of phosphorus. Furthermore, the results from the Standards, Measurements and Testing (SMT) and X-Ray Diffraction (XRD) showed that phosphorus in the AGS mainly existed in the form of inorganic phosphorus (IP) and the proportion of Ca5(PO4)3(OH) in IP was up to 92%. This investigation demonstrated that EPS had a positive relationship with the sludge granulation and nutrients removal.

Towards biomass production and wastewater treatment by enhancing the microalgae-based nutrients recovery from liquid digestate in an innovative photobioreactor integrated with dialysis bag.

Microalgae-based nutrients recovery from liquid anaerobic digestate of swine manure has been a hotspot in recent decades. Nevertheless, in consideration of the high NH4+-N content and poor light penetrability exhibited by the original liquid digestate, uneconomical pretreatment on liquid digestate including centrifugation and dilution are indispensable before microalgae cells inoculation. Herein, aiming at eliminating the energy-intensive and freshwater-consuming pretreatment on liquid digestate and enhancing microalgae growth, the dialysis bag which permits nutrients transferring across its wall surface whereas retains almost all matters characterized by impeding light transmission within the raw liquid digestate was integrated into a column photobioreactor (DB-PBR). Consequently, light availability of microalgae cells in DB-PBR was elevated remarkably and thus contributed to a 357.58% improvement on microalgae biomass concentration in DB-PBR than the conventional PBR under 80 µmol m-2 s-1. Likewise, superior nutrients removal efficiencies from liquid digestate were obtained in DB-PBR (NH4+-N: 74.84%, TP: 63.75%) over the conventional PBR (NH4+-N: 30.27%, TP: 16.86%). Furthermore, higher microalgae biomass concentration (1.87 g L-1) and nutrients removal efficiencies (NH4+-N: 95.12%, TP: 76.87%) were achieved in the DB-PBR by increasing the light intensity to 140 µmol m-2 s-1. More importantly, the DB-PBR may provide a simple and greener solution to purify other kinds of wastewater.

Impacts of seasonality and operating conditions on water quality of algal versus conventional wastewater treatment: Part 1.

Municipal wastewater is a reliable source from which water, renewable energy, and nutrients could be recovered for beneficial use. Our previous efforts have documented that an innovative algal-based wastewater treatment (WWT) system could recover energy and nutrients from wastewater while having a lower energy footprint than conventional WWT processes. As a biological treatment process, the algal WWT can be affected by algal species, operating conditions, and meteorological factors. This study aimed to identify suitable algal cultures to treat municipal wastewater during warm and cold weather. The algal system achieved the secondary effluent discharge standards for biochemical oxygen demand and nutrients within 2-3 days during warm weather (May to October, 25-55 °C) using an extremophilic algal strain Galdieria sulphuraria; and within 1-2 days in winter (November to April, 4-17 °C) using polyculture strains of algae with bacteria. The impact of seasonal variation and operating conditions on the water quality of pilot-scale algal bioreactors was compared with a full-scale conventional WWT system. The treatment performance of the algal system (NH4-N: 1.3 ± 1.25 mg/L in winter and not detected in summer and conventional system; PO4-P: 0.89 ± 0.6 mg/L in winter, 0.02 ± 0.03 mg/L in summer and, 5.93 ± 1.32 mg/L in conventional system) was comparable or better than that of the conventional WWT in nutrients removal and other contaminants were below the discharge standards. This study indicates that the algal system can be engineered for reliable wastewater treatment independent of seasonal variations.

A newly isolated microalga Chlamydomonas sp. YC to efficiently remove ammonium nitrogen of rare earth elements wastewater.

The aim of this study was to establish a practical approach to remove ammonium nitrogen of rare earth elements (REEs) wastewater by an indigenous photoautotrophic microalga. Firstly, a new microalgal strain was successfully isolated from REEs wastewater and identified as Chlamydomonas sp. (named Chlamydomonas sp. YC). The obtained results showed that microalga could completely remove the NH4+-N of 10% REEs wastewater after 10 days of cultivation; however, the highest NH4+-N removal rate was attained by microalga to treat undiluted REEs wastewater. Then, three cultivation modes including batch, semi-continuous and continuous cultivation methods were developed to evaluate the ability of NH4+-N removal rate by this microalga to treat diluted (10%) and undiluted REEs wastewater. It was found that, Chlamydomonas sp. YC exhibited superior performance towards NH4+-N removal rates (32.75-61.05 mg/(L·d)) by semi-continuous and continuous processes for the treatments of 10% and undiluted REEs wastewater in comparison to the results (19.50-30.38 mg/(L·d) by batch process. Interestingly, under the same treatment conditions, among the three cultivation modes, microalga exhibited the highest removal rates of NH4+-N in undiluted REEs wastewater by semi-continuous (61.05 mg/(L·d)) and continuous (57.10 mg/(L·d) processes. In term of the biochemical analysis, microalgal biomass obtained from the wastewater treatment had 35.40-44.40% carbohydrate and 4.97-6.03% lipid, which could be potential ingredients for sustainable biofuels production. And the highest carbohydrate and lipid productivities attained by Chlamydomonas sp. YC in the continuous mode were 226.36 mg/(L·d) and 32.98 mg/(L·d), respectively. Taken together, the established processes mediated with Chlamydomonas sp. YC via continuous cultivation was the great promising approaches to efficiently remove NH4+-N of REEs wastewater and produce valuable biomass for sustainable and renewable biofuels in a simultaneous manner.

Insights into bioflocculation of filamentous cyanobacteria, microalgae and their mixture for a low-cost biomass harvesting system.

Cyanobacteria and microalgae are considered as interesting feedstocks for either the production of high value bio-based compounds and biofuels or wastewater treatment. Nevertheless, the high costs of production, mainly due to the harvesting process, hamper a wide commercialization of industrial cyanobacteria and microalgae based products. Recent studies have found in autoflocculation and bioflocculation promising spontaneous processes for a low-cost and environmentally sustainable cyanobacteria and microalgae biomass harvesting process. In the present work, bioflocculation process has been studied for three different inocula: filamentous cyanobacteria, microalgae and their mixture. Their cultivation has been conducted in batch mode using two different cultivation media: synthetic aqueous solution and urban wastewater. The removal of nutrients and flocculation process performance were monitored during the entire cultivation time. Results have proved that bioflocculation and sedimentation processes occur efficiently for filamentous cyanobacteria cultivated in synthetic aqueous solution, whereas such processes are less efficient in urban wastewater due to the specific characteristics of this medium that prevent bioflocculation to occur. Besides different efficiencies associated to cultivation media, this work highlighted that bioflocculation of sole microalgae is not as effective as when they are cultivated together with filamentous cyanobacteria.

Responses of microbial communities and their interactions to ibuprofen in a bio-electrochemical system.

Ibuprofen has caused great concerns due to their potential environmental risks. However, their removal efficiency and their effects on microbial interactions in bio-electrochemical system remain unclear. To address these issues, a lab-scale bio-electrochemical reactor integrated with sulfur/iron-mediated autotrophic denitrification (BER-S/IAD) system exposing to 1000 µg L-1 ibuprofen was operated for about two months. Results revealed that the BER-S/IAD system obtained efficient simultaneous denitrification (98.93%) and phosphorus (82.67%) removal, as well as an excellent ibuprofen removal performance (96.98%). Ibuprofen had no significant impacts on the nitrate (NO3--N) removal and the ammonia (NH4+-N) accumulation, but decreased the total nitrogen (TN) and total phosphorus (TP) removal efficiencies. MiSeq sequencing analysis revealed that ibuprofen significantly (P < 0.05) decreased the microbial community diversity and changed their overall structure. Some bacteria related to denitrification and phosphorus removal, such as Pseudomonas and Thiobacillus, decreased significantly (P < 0.05). Moreover, molecular ecological network (MEN) analysis revealed that ibuprofen decreased the network's size and complexity, and enhanced the negative correlations of Proteobacteria and Firmicutes. Besides, ibuprofen decreased the links of some keystone bacteria related to denitrification and phosphorus removal. This research could provide a new dimension for our comprehending of the responses of microbial communities and their interactions to ibuprofen in bio-electrochemical system.

Advanced treatment of chicken farm flushing wastewater by integrating Fenton oxidation and algal cultivation process for algal growth and nutrients removal.

Algae based wastewater treatment has been considered as the most promising win-win strategy for nutrients removal and biomass accumulation. However, the poor linking between traditional wastewater treatment and algal cultivation limits the achievement of this goal. In this study, a novel combination of Fenton oxidation and algal cultivation (CFOAC) system was investigated for the treatment of chicken farm flushing wastewater (CFFW). Fenton oxidation (FO) was adopted to reduce the excessive ammonia nitrogen, which might inhibit the algal growth. The results showed that single FO pretreatment removed 70.5 %, 96.7 %, 86.1 %, and 96.2 % of TN, TAN, TP, and COD, respectively. The highest biomass (235.8 mg/L/d) and lipid (77.3 mg/L/d) productivities were achieved on optimized CFOAC system after 7 days batch cultivation. Accordingly, the nutrients removal efficiencies increased to almost 100 %. Further fatty acid profile analysis showed that algae grown on optimal CFOAC system accumulated a high level of total lipids (32.8 %) with C16-C18 fatty acid as the most abundant compositions (accounting for over 60.6 %), which were propitious to biodiesel production. In addition, this CFOAC system was magnified from 1 L flask to 50 L horizontal pipe photobioreactor (HPPB) in semi-continuously culture under optimal conditions. The average biomass and lipid productivities were 995.7 mg/L/d and 320.6 mg/L/d, respectively, when cultured at 6 days hydraulic retention time with 1/3 substitution every two days. These findings proved that the novel CFOAC system is efficient in nutrients removal, algal cultivation, and biomass production for advanced treatment of CFFW.

Enhancement of mariculture wastewater treatment using moving bed biofilm reactors filled with modified biocarriers: Characterisation, process performance and microbial community evaluation.

This research investigated two proposed modified biofilm carriers' performances in treating recirculating aquaculture systems (RAS) wastewater under different salinities (12‰, 26‰, and 35‰) for about 92 days. Three moving bed biofilm reactors (MBBRs; R1, R2, and R3) were filled with unmodified novel sponge biocarriers (SB) served as a control, modified novel SB with ferrous oxalate (C2FeO4@SB), and modified novel SB with combined ferrous oxalate and activated carbon (C2FeO4-AC@SB), respectively. Under the highest saline condition, a significantly higher ammonia removal efficiency of 98.86 ± 0.7% (p ˃ 0.05) was obtained in R3, whereas R2 and R1 yielded 95.18 ± 2.8% and 91.66 ± 1.5%, respectively. Microbial analysis showed that Vibrio, Ruegeria, Formosa, Thalassospira, and Denitromonas were predominant genera, strictly halophilic heterotrophic nitrifying bacteria involved in nitrogen removal. In conclusion, the synergistic effects of novel sponge, C2FeO4 and AC accelerated biofilm formations and stability, subsequently enhanced the removal of ammonia from the mariculture RAS wastewater by the C2FeO4-AC@SB carriers in R3.

Energy recovery and carbon/nitrogen removal from sewage and contaminated groundwater in a coupled hydrolytic-acidogenic sequencing batch reactor and denitrifying biocathode microbial fuel cell.

Developing cost-effective technology for treatment of sewage and nitrogen-containing groundwater is one of the crucial challenges of global water industries. Microbial fuel cells (MFCs) oxidize organics from sewage by exoelectrogens on anode to produce electricity while denitrifiers on cathode utilize the generated electricity to reduce nitrogen from contaminated groundwater. As the exoelectrogens are incapable of oxidizing insoluble, polymeric, and complex organics, a novel integration of an anaerobic sequencing batch reactor (ASBR) prior to the MFC simultaneously achieve hydrolytic-acidogenic conversion of complex organics, boost power recovery, and remove Carbon/Nitrogen (C/N) from the sewage and groundwater. The results obtained revealed increases in the fractions of soluble organics and volatile fatty acids in pretreated sewage by 52 ± 19% and 120 ± 40%, respectively. The optimum power and current generation with the pretreated sewage were 7.1 W m-3 and 45.88 A m-3, respectively, corresponding to 8% and 10% improvements compared to untreated sewage. Moreover, the integration of the ASBR with the biocathode MFC led to 217% higher carbon and 136% higher nitrogen removal efficiencies compared to the similar system without ASBR. The outcomes of the present study represent the promising prospects of using ASBR pretreatment and successive utilization of solubilized organics in denitrifying biocathode MFCs for simultaneous energy recovery and C/N removal from both sewage and nitrate nitrogen-contaminated groundwater.

Impact of cycle type on aerobic granular sludge formation, stability, removal mechanisms and system performance.

This paper aimed to assess the impact of the cycle type on aerobic granular sludge (AGS) formation, stability and system performance. Six AGS reactors were operated either on A/O cycles (anaerobic followed by oxic phase) or A/O/A cycles (anaerobic, followed by oxic and anoxic phases), changing only the phase time distribution. Reactors with high percentage of aerobic phase (65% of the total cycle time) generated granules with better settleability and resistance, however denitrification was impaired. On the other hand, reactors with long anaerobic or anoxic phases presented excellent nutrients removals, but the granules were fluffy and unstable. The best results in terms of performance and stability were achieved in an A/O/A reactor with short anoxic phase (10% of the total cycle) and medium aerobic phase (55% of the total cycle). Therefore, in AGS reactors, it is indispensable to optimize the cycle, aiming at fast biomass formation, long-term granule stability and high-rate pollutants removal.

Simultaneous sludge minimization, biological phosphorous removal and membrane fouling mitigation in a novel plant layout for MBR.

The integration of one anaerobic reactor in the mainstream (AMSR) of a pre-denitritication-MBR was evaluated with the aim to achieve simultaneous sludge minimization and phosphorous removal. The excess sludge production was reduced by 64% when the AMSR was operated under 8 h of hydraulic retention time (HRT). The highest nutrients removal performances referred to organic carbon (98%), nitrogen (90%) and phosphorous (97%) were obtained under 8 h of HRT. In contrast, prolonged anaerobic-endogenous conditions were found to be detrimental for all nutrients removal performances. Similarly, the lowest membrane fouling tendency (FR = 0.65∙1011 m-1 d-1) was achieved under 8 h of HRT, whereas it significantly increased under higher HRT. The highest polyphosphate accumulating organisms kinetics were achieved under HRT of 8 h, showing very high exogenous P-release (46.67 mgPO4-P gVSS-1 h-1) and P-uptake rates (48.6 mgPO4-P gVSS-1 h-1), as well as a not negligible P-release rate under endogenous conditions at low COD/P ratio (≈1).

Nutrient removal in an algal membrane photobioreactor: effects of wastewater composition and light/dark cycle.

Graesiella emersonii was cultivated in an osmotic membrane photobioreactor (OMPBR) for nutrients removal from synthetic wastewater in continuous mode. At 1.5 days of hydraulic retention time and under continuous illumination, the microalgae removed nitrogen (N) completely at influent NH4+-N concentrations of 4-16 mg/L, with removal rates of 3.03-12.1 mg/L-day. Phosphorus (P) removal in the OMPBR was through biological assimilation as well as membrane rejection, but PO43--P assimilation by microalgae could be improved at higher NH4+-N concentrations. Microalgae biomass composition was affected by N/P ratio in wastewater, and a higher N/P ratio resulted in higher P accumulation in the biomass. The OMPBR accumulated about 0.35 g/L biomass after 12 days of operation under continuous illumination. However, OMPBR operation under 12 h light/12 h dark cycle lowered biomass productivity by 60%, which resulted in 20% decrease in NH4+-N removal and nearly threefold increase in PO43--P accumulation in the OMPBR. Prolonged dark phase also affected carbohydrate accumulation in biomass, although its effects on lipid and protein accumulation were negligible. The microalgae also exhibited high tendency to aggregate and settle, which could be attributed to reduction in cell surface charge and enrichment of soluble algal products in the OMPBR. Due to a relatively shorter operating period, membrane biofouling and salt accumulation did not influence the permeate flux significantly. These results improve the understanding of the effects of N/P ratio and light/dark cycle on biomass accumulation and nutrients removal in the OMPBR.

Suitability of nutrients removal from brewery wastewater using a hydroponic technology with Typha latifolia.

BACKGROUND: This study aims to assess suitability of hydroponic technology for treatment of brewery wastewater in a hydroponic bioreactor using Typha latifolia. Triplicated hydroponic bioreactor treatment units were designed, constructed and operated at a hydraulic retention time of 5 days with different surface loadings and mean hydraulic loading rate 0.023 m3 m-2d- 1. Young T. latifolia shoots were collected in the vicinity of study site. Wastewater characteristics, plant growth and nutrient accumulation during experiment were analyzed as per APHA standard methods and nutrient removal efficiency was evaluated based on inlet and outlet values. RESULTS: T. latifolia established and grew well in the hydroponics under fluctuations of wastewater loads and showed a good phytoremedial capacity to remove nutrients. Significant removal efficiencies (p < 0.05) varied between 54 and 80% for Total Kjeldahl Nitrogen, 42 and 65% for NH4+ -N, 47 and 58% for NO3- -N, and 51 and 70% for PO43--P. The system improved the removal up to 29% compared to control and produced biomass of 0.61-0.86 kg dry weight (DW) m- 2. Nutrients retained were up to 21.17 g N kg- 1 DW and 2.87 g P kg- 1 DW. CONCLUSION: The significant nutrients reduction obtained and production of biomass led us to conclude that hydroponics technology using T. latifolia has suitability potential for treatment of brewery wastewater and similar agro-industrial wastewaters. Thus it could be considered as a promising eco-friendly option for wastewater treatment to mitigate water pollution. Integration of treatment and production of biomass needs further improvement.