Wastewater microbial diversity versus molecular analysis at a glance: a mini-review.

Microorganisms play a vital role in biological wastewater treatment by converting organic and toxic materials into harmless substances. Understanding microbial communities' structure, taxonomy, phylogeny, and metabolic activities is essential to improve these processes. Molecular microbial ecology employs molecular techniques to study community profiles and phylogenetic information since culture-dependent approaches have limitations in providing a comprehensive understanding of microbial diversity in a system. Genomic advancements such as DNA hybridization, microarray analysis, sequencing, and reverse sample genome probing have enabled the detailed characterization of microbial communities in wastewater treatment facilities. This mini-review summarizes the current state of knowledge on the diversity of microorganisms in wastewater treatment plants, emphasizing critical microbial processes such as nitrogen and phosphorus removal.

Low biological phosphorus removal from effluents treated by slow sand filters.

The legislation for environment protection requires strict controls of the wastewater releasing in water bodies. The wastewater treatment plants (WWTP) have been used for organic matter degradation; however, the residual total phosphorus (TP) removal has not been efficient. TP and nitrogen present in wastewater are associated to eutrophication of water bodies and algae growth. Therefore, this study discusses the efficiency of phosphorus removal by a slow filter (SF), complementary to a WWTP and the microbial community involved. The results showed that the use of SF, with or without macrophytes, is not suitable to remove TP. Spatial variation in microbial communities distributed in three distinct zones was identified in the SF. Proteobacteria, Bacteroidetes, Chloroflexi and Firmicutes covered the hydrolytic and fermentative bacteria. The acetogenesis, nitrification, and denitrification, as well as the removal of phosphorus from the effluent, were performed by representatives affiliated to different groups. Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria among these, Dokdonella sp., Frateuria sp., Comamonas sp., Diaphorobacter sp., Nitrosospira sp., Ferruginibacter sp., Flavobacterium sp., and the uncultured OD1 were the most abundant bacteria in the SF. The low efficiency for TP removing from SF effluents can be explained by the low abundance of phosphorus accumulating organisms (PAOs), with the association of the low concentration of biodegradable organic matter in the inlet effluent. Therefore, the alternative to using SF as a complement to WWTPs, as recommended by some Brazilian environmental agencies, did not prove to be viable and new approaches must be evaluated. KEY POINTS: • The phosphorus removal was performed by a slow filter system in a WWTP but obtained a low efficiency. • Microbial spatial variation was distributed into distinct zones from slow filter. • Low abundance of PAOs was observed due to the low availability of organic matter.

Formation and stability of aerobic granular sludge in a sequential batch reactor for the simultaneous removal of organic matter and nutrients from low-strength domestic wastewater.

Simultaneous removal of organic matter, nitrogen, and phosphorus, via simultaneous nitrification and denitrification (SND) and enhanced biological phosphorus removal processes, was evaluated in a pilot-scale sequential batch reactor. The focus was on granule's morphology, stability, microbiological composition, and reactor performance while treating diluted domestic wastewater with total chemical oxygen demand (CODt) of ≈ 200 mg.L-1. The applied organic loading rate was 0.9 ± 0.3 kg CODt.m-3.d-1 in the experiment. Aerobic granular sludge developed gradually. After 87-day operation, granules (diameter ≥ 0.2 mm) were ≥ 50 % of the biomass, and after 168 days, complete granulation was obtained (≥ 80 % of biomass). In the third period (days 168-247, complete granulation), mixed liquor biomass reached a volatile suspended solids (VSS) concentration of 1.2 ± 0.3 g VSS.L-1, with the granules remaining stable until the experimental end. In this period, low effluent concentrations of COD, nitrogen (NH4+-N, NO2--N and NO3--N) and phosphate (PO43-P) were obtained (mg.L-1): 36 ± 11; 4 ± 5; 3 ± 3, 4 ± 5; and 0.9 ± 0.4, respectively. COD, NH4+-N, and PO43--P removal efficiencies (%) were 80 ± 11; 83 ± 20; and 55 ± 24, respectively. Heterotrophic nitrification and SND were observed, resulting in a process efficiency of 31 % even with dissolved oxygen applied to saturation. The phosphate removal was mainly attributed to denitrifying phosphorus accumulating organisms. Pseudomonas, the dominant genus found, acted in nitrogen and phosphorus removal. Pseudoxanthomonas also assisted in phosphorus removal. Bacterial communities in the flocs (≈ 20 % of biomass) during the last period were similar to those in the granules; therefore, they constituted the basis for granule formation, directly contributed to the simultaneous good removal of organic matter and nutrients.

Virucidal activity of microalgae extracts harvested during phycoremediation of swine wastewater.

Phycoremediation of swine wastewater is a promising treatment since it efficiently removes nutrients and contaminants and, simultaneously, its biomass can be harvested and used to obtain a wide range of valuable compounds and metabolites. In this context, biomass microalgae were investigated for the phycoremediation of swine wastewater, and biomass extracts for its virucidal effect against enveloped and non-enveloped viruses. Microalgae were cultivated in a pilot scale bioreactor fed with swine wastewater as the growth substrate. Hexane, dichloromethane, and methanol were used to obtain the microalgae extracts. Extracts were tested for virucidal potential against HSV-1 and HAdV-5. Virucidal assays were conducted at temperatures that emulate environmental conditions (21 °C) and body temperature (37 °C). The maximum production of microalgae biomass reached a concentration of 318.5 ± 23.6 mgDW L-1. The results showed that phycoremediation removed 100% of ammonia-N and phosphate-P, with rates (k1) of 0.218 ± 0.013 and 0.501 ± 0.038 (day-1), respectively. All microalgae extract reduced 100% of the infectious capacity of HSV-1. The microalgae extracts with dichloromethane and methanol showed inhibition activities at the lowest concentration (3.125 µg mL-1). Virucidal assays against HAdV-5 using microalgae extract of hexane and methanol inhibited the infectious capacity of the virus by 70% at all concentrations tested at 37 °C. At a concentration of 12.5 µg mL-1, the dichloromethane microalgae extract reduced 50-80% of the infectious capacity of HAdV-5, also at 37 °C. Overall, the results suggest that the microalgae can be an attractive source of feedstock biomass for the exploration of alternative virucidal compounds.

Influence of HRT and carbon source on the enhancement of nutrient removal in an Anaerobic-Oxic-Anoxic (AOA) system.

The eutrophication and increase in toxicity promoted by the continuous or abundant supply of nutrients in water bodies threaten the safety of drinking water and human health. In this regard, this study proposes the investigation of wastewater treatment focusing on the simultaneous removal of nitrogen and phosphorus in the anaerobic-oxic-anoxic (AOA) system. The AOA system was operated in three different stages to verify the influence of the external carbon source addition in the anoxic reactor and the reduction of hydraulic retention time (HRT) in the anaerobic and oxic reactors for nutrient removal optimization. Results showed that the best performance of the AOA system on nutrient removal was obtained in Stage 3, with the reduction of the HRT in the anaerobic and oxic reactors (HRT = 4 h) while maintaining HRT of 6.4 h in the anoxic reactor with no addition of the external carbon source. Under these conditions, the average removal efficiencies reached 98% for Chemical Oxygen Demand (COD), 88% for Total Ammonia Nitrogen (TAN), 81% for Total Kjeldahl Nitrogen (TKN), and 70% for Total Phosphorus (TP). The results also demonstrate that the highest phosphorus removal efficiency was achieved in the anoxic reactor, thus indicating the occurrence of denitrifying phosphorous removal by Denitrifying Phosphate Accumulating Organisms (DNPAOs). This configuration was efficient regarding the simultaneous removal of nitrogen and phosphorus; besides, the advantages of this system include robust configuration and excellent performance on the nutrient removal.

Evaluation of long-term phosphorus uptake by Schoenoplectus californicus and Phragmites australis plants in pilot-scale constructed wetlands.

The aim of this study was to evaluate long-term phosphorus (P) retention in a pilot-scale system made of four horizontal subsurface flow (HSSF) constructed wetlands for wastewater treatment. Each wetland had an area of 4.5 m2 and was operated for nearly 8 years (2833 days). Two wetlands with Schoenoplectus californicus (HSSF-Sch) and the other two with Phragmites australis (HSSF-Phr) were planted. The P removal efficiency was 18% for both types of HSSF wetlands. The primary factors that correlated with long-term P retention efficiency in HSSF were phosphorus loading rate (PLR), hydraulic loading rate (HLR) and dissolved oxygen (DO). Average biomass production of HSSF-Phr and HSSF-Sch was 4.8 and 12.1 kg dry weight (DW)/m2, respectively. The P uptake by the plant increased over the years of operation from 1.8 gP/m2 to 7.1 gP/m2 for Phragmites and from 3.2 to 7.4 gP/m2 for Schoenoplectus over the same periods. Moreover, the warm season (S/Sm) was more efficient reaching 14% P uptake than the cold season (F/W) with 9%. These results suggest that both plants' P retention capacity in HSSF systems represents a sustainable treatment in the long term.Novelty statement Long-term (8 years) phosphorus uptake by Schoenoplectus californicus and Phragmites australis and retention in pilot-scale constructed wetlands are evaluated. Schoenoplectus californicus is an uncommon species that has been less studied for phosphorus uptake compared to Phragmites australis, a globally known species in constructed wetlands. Moreover, some studies evaluating the performance of constructed wetland systems for domestic wastewater treatment are usually limited in time (1-3 years). Therefore, this long-term study demonstrates that the plant plays an important role in phosphorus retention, especially the species Schoenoplectus californicus. So, the phosphorus uptake by plants can contribute between 9 and 14% of the phosphorus load of constructed wetland systems in early years of operation.

Eletrocoagulação como pós-tratamento do efluente de um wetland construído de escoamento vertical / Electrocoagulation as post-treatment of the effluent from a vertical flow constructed wetland

RESUMO A eletrocoagulação (EC) foi aplicada como tratamento terciário para o efluente de wetland construído de escoamento vertical (WCV). O sistema de EC compreendeu um reator cilíndrico de vidro (1 L) e eletrodos de alumínio conectados a uma fonte de alimentação de corrente contínua. O estudo foi desenvolvido em duas etapas. Na primeira, as condições operacionais do reator foram delimitadas por meio de um experimento bifatorial 32 (3×3) de natureza quantitativa × quantitativa, analisando intensidade de corrente e tempo. Com base nos resultados obtidos, a regressão linear resultou na combinação de 1,3 A e 18 min, com custo operacional elétrico de 2,71 R$.m−3. Em seguida, realizou-se a etapa de monitoramento durante quatro meses, aplicando a EC sob essas condições fixas estabelecidas. As eficiências médias de remoção alcançadas foram de 99,7% para P-PO43-, 20,6% para N-NO3−, 2,37 log de coliformes totais, 2,35 log de Escherichia coli, 84,9% para demanda química de oxigênio, 95% para turbidez, 95,1% para cor aparente, aumento de 19% no pH, de 18,6% na temperatura e diminuição de 15,8% na condutividade elétrica. O tratamento demonstrou elevadas e homogêneas eficiências de remoção dos poluentes, principalmente para P-PO43-, indicando que a EC produz efluente com menor potencial poluidor e é indicada para tratamento de efluente doméstico em nível terciário.

ABSTRACT Electrocoagulation (EC) was applied as a tertiary treatment for the effluent of a vertical flow constructed wetland (VFCW). The EC system was composed of a cylindrical glass reactor (1 L) and aluminum electrodes connected to a DC power supply. The study was developed in two stages. In the first, the reactor operating conditions were set by a 32 (3×3) two-factor experiment, quantitative × quantitative, analyzing current intensity and time (current × time). Based on the results, the linear regression resulted in the combination of 1.3 A and 18 min, with an electric operation cost of 2.71 $.m−3. Next, the monitoring stage was conducted for four months, applying the EC under the established conditions. The mean removal efficiencies were 99.6% for P-PO43-, 20.6% for N-NO3−, 2.37 log of total coliforms, 2.35 log of Escherichia coli, 84.8% for chemical oxygen demand, 94.9% for turbidity, 95% for apparent color, an increase of 18.9% in pH and of 18.6% in temperature, and a decrease of 15.8% in electrical conductivity. The treatment showed high and homogeneous pollutant removal efficiencies, mainly for P-PO43-, indicating that the EC produces an effluent with lower polluting potential and it is recommended in the tertiary treatment of domestic wastewater.

Emulating natural wetlands oxygen conditions for the removal of N and P in agricultural wastewaters.

The aim of this research was to evaluate a constructed wetland system (CW) operated under aerobic-anoxic-aerobic conditions to remove C, N and P from water with high concentrations of the last two nutrients. A series of three CW were operated continuously for 190 days. An aerobic vertical CW was used in the first and third stages and an anoxic horizontal CW was used in the second stage. The total nitrogen (TN) removal efficiency was 70 ±â€¯1.5%. Similar removal efficiency behavior was observed in others nitrogen compounds, where a removal of 85 ±â€¯1.5% for NO3--N and 97 ±â€¯2.2% for NH3+N were achieved. The combination of different oxygen conditions enhanced oxidation of nitrates and the assimilation of ammonium by vegetation. On the other hand, 54 ±â€¯6.5% total phosphorus (TP) was removed in the entire system, which is higher than the reported in several investigations, including mechanized and controlled systems such as activated sludge. The phosphorous removal efficiency was attributed to the adequate design and configuration of CW, which facilitated dissolved oxygen (DO) conditions required for phosphorus capture. Despite in this investigation the CW was not designed for an optimal removal of organic matter the removal efficiency of this parameter was 64 ±â€¯7.5%. The successful results suggest that the combination of aerobic-anoxic-aerobic stages is a technically suitable option for the treatment of agricultural wastewater with high content of N and P.

Effect of acetate to glycerol ratio on enhanced biological phosphorus removal.

Enhanced biological phosphorus removal (EBPR) is a sustainable and promising technology for phosphorus removal from wastewater. The efficiency of this technology, however, is often discounted due to the insufficient carbon sources in influent. In this work, the effect of acetate to glycerol ratio on the EBPR performance was evaluated. The experimental results showed when the ratio of acetate to glycerol decreased from 100/0% to 50/50%, the EBPR efficiency increased from 90.2% to 96.2%. Further decrease of acetate to glycerol ratio to 0/100% decreased the efficiency of EBPR to 30.5%. Fluorescence in situ hybridization analysis demonstrated appropriate increase of glycerol benefited to increase the relative abundance of phosphate accumulating organisms. Further investigation revealed the proper addition of glycerol increased the amount of polyhydroxyalkanoates synthesis, and then produced sufficient energy for oxic luxury phosphorus in the subsequent oxic phase.

Tratamento de esgoto sanitário em reator híbrido em bateladas sequenciais: eficiência e estabilidade na remoção de matéria orgânica e nutrientes (N, P) / Sewage treatment in a sequencing batch hybrid reactor: efficiency and stability in organic matter and nutrient (N, P) removal

Este trabalho apresenta os resultados de estudo sobre o comportamento de um reator híbrido, operado em bateladas sequenciais, na remoção conjunta de matéria carbonácea, nitrogênio e fósforo de esgoto sanitário. Operado em ciclos de 8 horas de duração, o reator possuía em seu interior um suporte fixo com rede de nylon. Foram testadas cargas compreendidas entre 0,39 e 1,35 kgDQO.m-3.dia-1, 42 e 60 gN-NH4-.m-3.dia e 51 e 70 gP-PO4-.m-3.dia. O reator funcionou como um sistema estável e apresentou boas condições de depuração. A remoção da matéria carbonácea mostrou-se elevada, com eficiências médias de 92 por cento de DBO5 e 80 por cento de DQO. A remoção de nutrientes variou entre 59 e 71 por cento para nitrogênio total e entre 45 e 67 por cento para fósforo total. Tanto no lodo em suspensão, quanto no biofilme, foi observada a ocorrência de bactérias oxidadoras de amônio e micro-organismos responsáveis pela desnitrificação e remoção biológica de fósforo.

This paper presents the results about the behavior of a sequencing batch hybrid reactor on combined removal of carbonaceous matter, nitrogen and phosphorus from sewage. Operated in 8-hour cycles, the reactor had a nylon net fixed inside. Loads between 0.39 and 1.35 kg COD.m-3.day-1, 42 and 60 gN-NH4-m-3.day-1 and 51 and 70 gP-PO4-m-3.day-1 were tested. The reactor operated as a stable system and showed good depuration conditions. The carbonaceous matter removal was high, with 92 and 80 percent efficiencies average to BOD5 and COD, respectively. The nutrients removal varied between 59 and 71 percent for total nitrogen and between 45 and 67 percent for total phosphorus. In both, sludge in suspension and the biofilm, occurrence of ammonium-oxidizing bacteria and microorganisms responsible for denitrification and biological phosphorus removal was observed.

Remoção biológica de fósforo em reatores em bateladas sequenciais com diferentes tempos de retenção de sólidos / Biological phosphorus removal in sequencing batch reactors with different solid retention times

Nos últimos anos, tem surgido a necessidade de se projetarem sistemas de tratamento de águas residuárias que, além de remover carga orgânica, sejam capazes de remover nutrientes, particularmente nitrogênio e fósforo. Este trabalho avaliou a remoção biológica de fósforo em sistemas de lodo ativado, tratando esgoto doméstico por meio de reatores em bateladas sequenciais (RBS), monitorado com diferentes tempos de retenção celular (TRC): 20, 5 e 3 dias. Esses experimentos foram avaliados em escala de bancada com o uso da respirometria, utilizando-se acetato como fonte de carbono orgânico. Os resultados mostraram satisfatória remoção de fósforo total nos três experimentos, com valores médios entre 79 a 82 por cento, sendo que o sistema RBS que operou com TRC de cinco dias obteve resultados melhores.

In recent years, there has been an increasing need to design wastewater treatment systems that are capable of removing both organic material and nutrients, notably nitrogen and phosphorus. This study evaluated biological phosphorus removal by activated sludge systems fed with domestic sewage and operating as sequencing batch reactors (SBR) with different solids retention times (SRT) namely 20, 5 and 3 days. This was supported by respirometry experiments at bench scale using acetate as the source of organic carbon. The results showed satisfactory total phosphorus removal efficiencies mean values between 79-82 percent for the three regimes with the best removal efficiency occurring in the SBR operating with a five-day SRT.

Produção de lodo e comportamento químico de sais de ferro empregados no pós-tratamento de esgoto sanitário por precipitação química / Sludge production and chemical behavior of iron salts employed in the post-treatment of sanitary wastewater by chemical precipitation

A combinação de processos físico-químicos e biológicos no tratamento de esgotos sanitários tem se apresentado como uma alternativa na remoção de fósforo. No entanto, uma das limitações é a sua maior produção de lodo. Desse modo, este trabalho teve por objetivo avaliar a produção de lodo resultante da aplicação de sais de ferro para diferentes tipos de efluentes, bem como estudar o impacto de sua aplicação nas características físico-químicas dos efluentes estudados. Concluiu-se que os valores médios de produção de lodo resultante da formação do hidróxido férrico situaram-se em torno de 1,80; 1,95 e 1,34 mg lodo/mg Fe+3 para esgoto bruto, efluente aeróbio e anaeróbio tratado, respectivamente, indicando que as características da fase líquida não influenciaram os mecanismos de precipitação dos íons férricos.

The combination of physical-chemical and biological processes in sanitary wastewater treatment has been employed as an alternative for phosphorus removal; however, one of its limitations is its large sludge production. This work aimed at evaluating the sludge production which resulted from iron salt application to different types of effluents, as well as studying the impacts of iron salt application on the physical-chemical characteristics of the studied effluents. It was concluded that the average sludge production values which resulted from ferric hydroxide formation were around 1.80, 1.95 and 1.34 mg sludge per mg of Fe+3 ion, with regard to raw wastewater, aerobic treated effluent and anaerobic treated effluent, respectively, thus indicating that the liquid phase characteristics did not influence the ferric ion precipitation mechanisms.

Otimização de processos físico-químicos na remoção de fósforo de esgotos sanitários por processos de precipitação química com cloreto férrico / Physical-chemical process optimization for phosphorus removal from domestic wastewater by chemical precipitation with ferric chloride

Tendo em vista a potencialidade do emprego de processos de coagulação química no tratamento de esgotos, este trabalho teve por objetivo estudar a remoção de fósforo em efluentes de sistemas anaeróbios e aeróbios de tratamento de esgotos. Observou-se que foi possível atingir valores de remoção de fósforo da ordem de 90%, sendo que as dosagens de coagulante se situaram em torno de 60 a 100 mg FeCl3/L. Concomitantemente com a remoção de fósforo, foi também observada uma remoção de carbono orgânico dissolvido (COD) para os efluentes investigados, sendo que as dosagens de coagulanteque permitiram a otimização da remoção de fósforo também possibilitaram a otimização da remoção de COD. Justifi ca-se a remoção de fósforo na forma orgânica e de polifosfatos pelo fato destes estarem associados ao COD removido.

Since chemical coagulation processes are very promising for wastewater treatment, this work looked into phosphorus removal from aerobic and anaerobic systems treating domestic wastewater. It was possible to reach phosphorus removal effi ciencies in theorder of 90 % for coagulant dosages in the range 60 to 100 mg of ferric chloride per liter. Dissolved organic carbon (DOC) removal in parallel with phosphorus removal was observed for the previously mentioned treatment system effl uents. The coagulant dosages for optimized phosphorus removal also led to optimum DOC removal. The removal of organic phosphorus fractions as polyphosphates was justifi ed due its association with the DOC removal by chemical precipitation.