Limitation of sludge biotic index application for control of a wastewater treatment plant working with shock organic and ammonium loadings

This study aimed to determine the relationship between activated sludge microfauna, the sludge biotic index (SBI) and the effluent quality of a full-scale municipal wastewater treatment plant (WWTP) working with shock organic and ammonium loadings caused by periodic wastewater delivery from septic tanks. Irrespective of high/low effluent quality in terms of COD, BOD₅, ammonium and suspended solids, high SBI values (8–10), which correspond to the first quality class of sludge, were observed. High SBI values were connected with abundant taxonomic composition and the domination of crawling ciliates with shelled amoebae and attached ciliates. High SBI values, even at a low effluent quality, limit the usefulness of the index for monitoring the status of an activated sludge system and the effluent quality in municipal WWTP-treated wastewater from septic tanks. It was shown that a more sensitive indicator of effluent quality was a change in the abundance of attached ciliates with a narrow peristome (Vorticella infusionum and Opercularia coarctata), small flagellates and crawling ciliates (Acineria uncinata) feeding on flagellates.     

The microfauna communities and operational monitoring of an activated sludge plant in China

The composition of the microfauna community in aeration tanks at the Baoding Sewage Treatment Plant in China was analysed each week from July 2002 to July 2003. The community composition of these microfauna populations was compared with effluent quality data recorded on the same days. A total of 94 species of ciliates, 40 species of amoebae and 13 species of large flagellates were identified in the 50 samples analysed. Numbers of metazoa including rotifers, nematodes, gastrotrichs and oligochaeta were also recorded. Although, Aspidisca cicada showed the highest mean abundance and was present in 98% of the samples, factor analysis revealed, among other things, that high Vorticella convallaria and Arcella hemisphaerica populations correlated with good performance of the treatment plant, while high numbers of Litonotus obtusus indicated poor conditions for settlement of sludge. These results show some agreement with an earlier study of sewage plants in Beijing, but analysis of more plants having a diversity of input components working under a range of different operating conditions should be performed to gain a general understanding of the value of indicator species for predicting the efficiency of activated sludge plants in China.     

Relationship between protozoan and metazoan communities and operation and performance parameters in a textile sewage activated sludge system

The present study aims at investigating the possibility of assessing performance and depuration conditions of an activated sludge wastewater treatment plant through an exploration of the microfauna. The plant, receiving textile industrial (70%) and domestic (30%) sewage, consists of a two-step biological depurating plant, with activated sludge followed by a percolating system. A total of 35 samples were analyzed during five months, and 30 taxa of protozoa and small metazoa were found. Epistylis rotans, Vorticella microstoma, Aspidisca cicada and Arcella sp. were the most frequent protozoa identified. Several significant correlations between biological, physical–chemical and operational parameters were determined, but no significant correlations could be established between biological parameters and removal efficiencies. The Sludge Biotic Index (SBI) reflected the overall state of the community but only presented statistically significant correlations with the influent total suspended solids (TSS), total suspended solids in mixed-liquor (MLTSS) and dissolved oxygen (DO). The determination of key groups and taxa along with general community parameters showed to have potential value as indicators of the depuration conditions. Despite the impossibility of correlating biological parameters and the removal efficiencies, the present study attests the value of the microfauna to assess the operation of the activated sludge systems even in the case of non-conventional plants and/or plants receiving industrial sewage.     

A New Species of the Genus Metacystis (Ciliophora,Prostomatida, Metacystidae) from a Wastewater Treatment Plant

ABSTRACT. Unusual prostomatid specimens were found in the biological reactor of a wastewater treatment plant in a health resort in Valencia, Spain. These ciliates were attached to flocs unlike other free‐swimming prostomatid ciliates described to date in the mixed liquor of activated sludge plants. The morphological study of this species led to a typically different combination of characteristics: elongated cell shape, 20–30 somatic kineties, 2 perioral kineties, and 1 circumoral kinety, 1 large vacuole protruding at the terminal end, a lorica tapered toward the aperture with a smooth neck, and 11–16 annular ridges. These characteristics place this representative as a new species of the genus Metacystis—Metacystis galiani n. sp. This species became the dominant population within the biological reactor when high values of conductivity (4,244 mS/cm) and temperature (26.8 °C) were recorded.     

The influence of fundamental design parameters on ciliates community structure in Irish activated sludge systems

The protozoan community in eleven activated sludge wastewater treatment plants (WWTPs) in the greater Dublin area has been investigated and correlated with key physio-chemical operational and effluent quality parameters. The plants represented various designs, including conventional and biological nutrient removal (BNR) systems. The aim of the study was to identify differences in ciliate community due to key design parameters including anoxic/anaerobic stages and to identify suitable bioindicator species for performance evaluation. BNR systems supported significantly different protozoan communities compared to conventional systems. Total protozoan abundance was reduced in plants with incorporated anoxic and anaerobic stages, whereas species diversity was either unaffected or increased. Plagiocampa rouxi and Holophrya discolor were tolerant to anoxic/anaerobic conditions and associated with high denitrification. Apart from process design, influent wastewater characteristics affect protozoan community structure. Aspidisca cicada was associated with low dissolved oxygen and low nitrate concentrations, while Trochilia minuta was indicative of good nitrifying conditions and good sludge settleability. Trithigmostoma cucullulus was sensitive to ammonia and phosphate and could be useful as an indicator of high effluent quality. The association rating assessment procedure of Curds and Cockburn failed to predict final effluent biological oxygen demand (BOD₅) indicating the method might not be applicable to treatment systems of different designs.     

Protozoan and metazoan communities treating a simulated petrochemical industry wastewater in a rotating disc biological reactor

The microfauna of adhered biofilms treating a simulated petrochemical plant wastewater was investigated in relation to the organic loading and the toxicity. Experiments in a six-compartment laboratory rotating biological reactor were performed at organic loadings of 0.99, 1.38 and 1.97g/l.day. The concentration of organic compounds in the artificial wastewater (phenol, acetophenone and styrene), toxicity of the wastewater, number of representative types of microfauna, their biomass and species diversity were monitored along the reactor. During this study 25 species were identified and attributed to seven classes of the three types Sarcomastigophora, Ciliophora and Nemathelminthes. Eight species from 18 ciliates have been reported in the literature as being commonly found inhabitants of aerobic wastewater treatment plants. An inverse relationship between the number of microfauna representatives and the organic loading was found. The presence of the most common species was related to the reactor operating conditions. A correlation between the toxicity of the wastewater measured by the Paramecium express-test and the distribution and abundance of microfauna was established. This express-test made it possible to predict the biological quality of the biofilm of activated sludge. Therefore, it is recommended as one of the control parameters to monitor systems of biological wastewater treatment.     

Biodiversity analysis of microbial community in the chem-bioflocculation treatment process

Total DNA was directly extracted from environmental samples and amplified with polymerase chain reaction (PCR) technique. The PCR products were fingerprinted via denaturing gradient gel electrophoresis (DGGE). Significant differences were observed in the microbial community structures between traditional treatment process and chem-bioflocculation process. The microbial community structure shift at different sampling locations in chem-bioflocculation process and on two typical operational conditions was studied. 16S rDNA V3 regions of some dominant species were sequenced and the species were identified. The microbial communities were stable in both the chem-bioflocculation process and the activated sludge process under various experimental conditions presented in this work. The attached growth treatment process was less stable when operational conditions changed.     

The influence of soluble microbial products on microbial community composition: hypothesis of microbial community succession

Soluble microbial products (SMP) are organic compounds produced by activated sludge microorganisms as they degrade substrates. They include by-products of microbial activity, death and lysis. The available literature does not reveal how SMP influence microbial community composition. In this regard, we microscopically studied changes in composition of microbial communities, especially protozoa and metazoa, under the influence of increased as well as reduced levels of SMP. The presence of SMP at high level significantly caused changes in microbial community composition. Microbial species shifted from attached ciliates (12-175 microm) to free-swimming and crawling ciliates (35-330 microm) and then invertebrates, which included rotifers (0.2-1 mm) and nematodes (1-50 mm). The shift of small-size microorganisms to large ones was observed as one of the most significant influences of SMP. Attached ciliates reappeared when we removed the SMP that had accumulated in the bioreactors - we have called this as the resurrection phenomenon of microorganisms. Such rapid changes in microbial community composition were not observed in the experiment with low concentration of SMP. Overall, the results suggest that accumulation of SMP is one of the intrinsic regulatory mechanisms that control viability and dormancy of microbial communities in activated sludge.     

Determination of some rheological parameters for the characterization of activated sludge

The rheological characterization of activated sludge originating from different aeration tanks and from a lab-scale plant was carried out using rotation tests. Two rheological parameters were used: limit viscosity (mu(infinity)) and reduced hysteresis area (rHa). Mu(infinity) was strongly influenced by the total suspended solids (TSS) content of sludge and an exponential relation was found between TSS and the rheological parameter mu(infinity). Significant differences in sludge viscosity were found for sludge of different origins, but all of 10 g/l TSS content, indicating ability of viscosity to show different sludge qualities. Marked changes in activated sludge microorganisms communities were shown to have an influence on rheological parameters. During aerobic digestion of sludge, variations in mu(infinity) were noticed, indicating change of sludge quality. An over-growth of filamentous bacteria species was shown to induce a particular rheological behavior which could be characterized by rHa. This parameter was proposed as an index of filamentous bacteria proliferation in activated sludge aeration tanks.     

Detection of anaerobic processes and microorganisms in immobilized activated sludge of a wastewater treatment plant with intense aeration

Attached activated sludge from the Krasnaya Polyana (Sochi) wastewater treatment plant was studied after the reconstruction by increased aeration and water recycle, as well as by the installation of a bristle carrier for activated sludge immobilization. The activated sludge biofilms developing under conditions of intense aeration were shown to contain both aerobic and anaerobic microorganisms. Activity of a strictly anaerobic methanogenic community was revealed, which degraded organic compounds to methane, further oxidized by aerobic methanotrophs. Volatile fatty acids, the intermediates of anaerobic degradation of complex organic compounds, were used by both aerobic and anaerobic microorganisms. Anaerobic oxidation of ammonium with nitrite (anammox) and the presence of obligate anammox bacteria were revealed in attached activated sludge biofilms. Simultaneous aerobic and anaerobic degradation of organic contaminants by attached activated sludge provides for high rates of water treatment, stability of the activated sludge under variable environmental conditions, and decreased excess sludge formation.     

The Role of Protozoa in the Activated-Sludge Process

Ciliates are the dominant protozoa in activated sludge, andthose which either attach themselves to or crawl over the surfaceof the sludge are the most common. Experimental work has demonstratedthat ciliated protozoa are essential for the production of agood quality effluent. Without ciliates, highly turbid, lowquality effluents are obtained. Experimental evidence furthersuggests that the predatory activities of the ciliates uponthe dispersed growths of bacteria are responsible for clarificationand for the reduction of coliform numbers during the activated-sludgeprocess. Mathematical models have been devised which take intoaccount both the bacterial and the protozoan populations. Thepopulations have been simulated on a computer and the resultsobtained in this way have helped to explain many of the observationsthat have been made upon the microbial populations found infull-scale activated-sludge plants.     

活性污泥中菌群多样性及其功能调控研究进展

活性污泥是污水处理厂生物处理工艺的功能主体,活性污泥中菌群的种类、数量及活性是提高污水处理能力与效果的重要基础。本文综述了活性污泥处理工艺中的主要功能细菌(絮凝菌、脱氮菌、除磷菌等)生物群落的多样性与生态特征,并对目前主流的菌群鉴定方式进行总结,最后从运行条件、定向驯化及生物强化3个方面对菌群调控进行论述,以期为活性污泥法污水处理工艺提供一些理论指导。     

Soil ciliate species richness and abundance associated with the rhizosphere of different subtropical plant species

Soil protozoa, and ciliates in particular, represent a microbial group abundant in the rhizosphere with an influential role on nutrient cycling. Under laboratory conditions, ciliates regulate the size and the composition of bacterial communities, and appear to stimulate ammonification and nitrification. In spite of their important ecological role, our understanding about the factors that control their diversity and abundance in natural forest ecosystems is still rudimentary. Plant species-specific interactions have been demonstrated between plants and soil bacteria and mycorrhizal fungi, due in part to the release of phytohormones and C- and N-rich exudates. We tested the hypothesis that the rhizosphere environments of different plant species also influence the species richness and abundance of soil ciliates. Plant effect, soil pH, moisture content, microbial biomass C, and inorganic nitrogen were measured among five plant species to determine the best predictor variables for soil ciliate species richness and total abundance in a subtropical moist forest in Puerto Rico. Based on an analysis of variance, we rejected the hypothesis that there was a plant species-specific effect on soil ciliates, unlike other microbial groups mentioned above. Using multiple regression analysis, we demonstrated that the flush of total inorganic nitrogen was the best predictor variable for both species richness and abundance of ciliates.     

Overexpression in Escherichia coli of the AT-rich trpA and trpB genes from the hyperthermophilic archaeon Pyrococcus furiosus

Micromanipulation was used to obtain an isolate (BEN 52) of Eikelboom Type 1851 from a bulking activated sludge plant. Its 16S rDNA sequence reveals its closest relative is 'Roseiflexus castenholzii', a member of the phylum 'Chloroflexi', class 'Chloroflexi', previously called the green non-sulfur bacteria. The 16S rRNA targeted oligonucleotide probe designed for fluorescence in situ hybridisation against this sequence successfully identified filamentous bacteria with the morphological features of Type 1851 in activated sludge samples from plants in several countries and different operational configurations.     

Microbiological parameters as an additional tool to improve wastewater treatment plant monitoring

The operation of an activated sludge wastewater treatment plant (WWTP) was assessed by determining the removal efficiency of treatment processes. For that purpose, different physicochemical and microbiological parameters, including total, active and culturable bacteria, were measured along a year. Values of both physicochemical and microbiological parameters were significantly reduced by biological treatment but no relation between these groups of parameters was obtained. Besides, results suggest that microbiological parameters were more sensitive than physicochemical ones to changes in WWTP conditions (i.e. influent quality). Additionally, high percentages of noncultured (>88%) and noncultured remaining active (until 50%) cells were detected before and after treatment. Therefore, ISO standards adopted to enumerate indicator bacteria by Spanish legislation, and based on culturability, underestimate the bacterial population present in wastewater. We have compared two culture-independent methods for bacterial enumeration, microscopy and flow cytometry (FCM) and results indicate that FCM provides a rapid and automated quantification in WWTP. We conclude that microbiological parameters are essential to monitor the correct WWTP operation and we propose quantification of active bacteria as indicator of wastewater microbiological quality.     

Diversity and dynamics of Archaea in an activated sludge wastewater treatment plant

ABSTRACT: BACKGROUND: The activated sludge process is one of the most widely used methods for treatment of wastewater and the microbial community composition in the sludge is important for the process operation. While the bacterial communities have been characterized in various activated sludge systems little is known about archaeal communities in activated sludge. The diversity and dynamics of the Archaea community in a full-scale activated sludge wastewater treatment plant were investigated by fluorescence in situ hybridization, terminal restriction fragment length polymorphism analysis and cloning and sequencing of 16S rRNA genes. RESULTS: The Archaea community was specialized and dominated by Methanosaeta-like species. During a 15 month period major changes in the community composition were only observed twice despite seasonal variations in environmental and operating conditions. Water temperature appeared to be the process parameter that affected the community composition the most. Several terminal restriction fragments also showed strong correlations with sludge properties and effluent water properties. The Archaea were estimated to make up 1.6-% of total cell numbers in the activated sludge and were present both as single cells and colonies of varying sizes. CONCLUSIONS: The results presented here show that Archaea can constitute a constant and integral part of the activated sludge and that it can therefore be useful to include Archaea in future studies of microbial communities in activated sludge.     

Bacterial community dynamics in long‐term operation of a pilot plant using aerobic granular sludge to treat pig slurry

Aerobic granular sludge represents an interesting approach for simultaneous organic matter and nitrogen removal in wastewater treatment plants. However, the information about microbial communities in aerobic granular systems dealing with industrial wastewater like pig slurry is limited. Herein, bacterial diversity and dynamics were assessed in a pilot scale plant using aerobic granular sludge for organic matter and nitrogen elimination from swine slurry during more than 300 days. Results indicated that bacterial composition evolved throughout the operational period from flocculent activated sludge, used as inoculum, to mature aerobic granules. Bacterial diversity increased at the beginning of the granulation process and then declined due to the application of transient organic matter and nitrogen loads. The operational conditions of the pilot plant and the degree of granulation determined the microbial community of the aerobic granules. Brachymonas, Zoogloea and Thauera were attributed with structural function as they are able to produce extracellular polymeric substances to maintain the granular structure. Nitrogen removal was justified by partial nitrification (Nitrosomonas) and denitrification (Thauera and Zoogloea), while Comamonas was identified as the main organic matter oxidizing bacteria. Overall, clear links between bacterial dynamics and composition with process performance were found and will help to predict their biological functions in wastewater ecosystems improving the future control of the process. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1212–1221, 2016     

Application of a Novel Functional Gene Microarray to Probe the Functional Ecology of Ammonia Oxidation in Nitrifying Activated Sludge

We report on the first study trialling a newly-developed, functional gene microarray (FGA) for characterising bacterial and archaeal ammonia oxidisers in activated sludge. Mixed liquor (ML) and media biofilm samples from a full-scale integrated fixed-film activated sludge (IFAS) plant were analysed with the FGA to profile the diversity and relative abundance of ammonia-oxidising archaea and bacteria (AOA and AOB respectively). FGA analyses of AOA and AOB communities revealed ubiquitous distribution of AOA across all samples – an important finding for these newly-discovered and poorly characterised organisms. Results also revealed striking differences in the functional ecology of attached versus suspended communities within the IFAS reactor. Quantitative assessment of AOB and AOA functional gene abundance revealed a dominance of AOB in the ML and approximately equal distribution of AOA and AOB in the media-attached biofilm. Subsequent correlations of functional gene abundance data with key water quality parameters suggested an important functional role for media-attached AOB in particular for IFAS reactor nitrification performance and indicate possible functional redundancy in some IFAS ammonia oxidiser communities. Results from this investigation demonstrate the capacity of the FGA to resolve subtle ecological shifts in key microbial communities in nitrifying activated sludge and indicate its value as a tool for better understanding the linkages between the ecology and performance of these engineered systems.     

Bacterial community composition and diversity of a full-scale integrated fixed-film activated sludge system as investigated by pyrosequencing

The integrated fixed-film activated sludge (IFAS) system is a variation of the activated sludge wastewater treatment process, in which hybrid suspended and attached biomass is used to treat wastewater. Although the function and performance of the IFAS system are well studied, little is known about its microbial community structure. In this study, the composition and diversity of the bacterial community of suspended and attached biomass samples were investigated in a full-scale IFAS system using a highthroughput pyrosequencing technology. Distinct bacterial community compositions were examined for each sample and appeared to be important for its features different from conventional activated sludge processes. The abundant bacterial groups were Betaproteobacteria (59.3%), Gammaproteobacteria (8.1%), Bacteroidetes (5.2%), Alphaproteobacteria (3.9%), and Actinobacteria (3.2%) in the suspended sample, whereas Actinobacteria (14.6%), Firmicutes (13.6%), Bacteroidetes (11.6%), Betaproteobacteria (9.9%), Gammaproteobacteria (9.25%), and Alphaproteobacteria (7.4%) were major bacterial groups in the attached sample. Regarding the diversity, totals of 3,034 and 1,451 operational taxonomic units were identified at the 3% cutoff for the suspended and attached samples, respectively. Rank abundance and community analyses demonstrated that most of the diversity was originated from rare species in the samples. Taken together, the information obtained in this study will be a base for further studies relating to the microbial community structure and function of the IFAS system.     

Plant Trait Assembly Affects Superiority of Grazer's Foraging Strategies in Species-Rich Grasslands

Background

Current plant – herbivore interaction models and experiments with mammalian herbivores grazing plant monocultures show the superiority of a maximizing forage quality strategy (MFQ) over a maximizing intake strategy (MI). However, there is a lack of evidence whether grazers comply with the model predictions under field conditions.

Methodology/Findings

We assessed diet selection of sheep (Ovis aries) using plant functional traits in productive mesic vs. low-productivity dry species-rich grasslands dominated by resource-exploitative vs. resource-conservative species respectively. Each grassland type was studied in two replicates for two years. We investigated the first grazing cycle in a set of 288 plots with a diameter of 30 cm, i.e. the size of sheep feeding station. In mesic grasslands, high plot defoliation was associated with community weighted means of leaf traits referring to high forage quality, i.e. low leaf dry matter content (LDMC) and high specific leaf area (SLA), with a high proportion of legumes and the most with high community weighted mean of forage indicator value. In contrast in dry grasslands, high community weighted mean of canopy height, an estimate of forage quantity, was the best predictor of plot defoliation. Similar differences in selection on forage quality vs. quantity were detected within plots. Sheep selected plants with higher forage indicator values than the plot specific community weighted mean of forage indicator value in mesic grasslands whereas taller plants were selected in dry grasslands. However, at this scale sheep avoided legumes and plants with higher SLA, preferred plants with higher LDMC while grazing plants with higher forage indicator values in mesic grasslands.

Conclusions

Our findings indicate that MFQ appears superior over MI only in habitats with a predominance of resource-exploitative species. Furthermore, plant functional traits (LDMC, SLA, nitrogen fixer) seem to be helpful correlates of forage quality only at the community level.