A national survey of activated sludge separation problems in The Czech republic: Filaments,floc characteristics and activated sludge metabolic properties

The extent of activated sludge separation problems associated with excessive growth of filamentous microorganisms has increased recently in the Czech Republic. Most of the activated sludge plants in the country were contacted by mail with a questionnaire, the aim of which was to obtain the basic technological data on the plants and on the nature and intensity of activated sludge separation problems. Selected activated sludge plants were visited at different periods of the year and samples of activated sludge mixed liquor and foam were collected for microscopic examination and kinetic batch tests. It was found that good settling properties were associated more with good quality activated sludge flocs than with the absence of filaments. On the other hand, a very high abundance of filaments always resulted in bulking or foaming. The most common tilamentous microorganisms in activated sludge mixed liquors were M. parvicella, N. limicola and Types 0092,0041 and 0803 while the foams were mostly dominated by M. parvicella, NALOs (GALOs) and N. limicola. Seasonal shifts in filamentous population diversity were also observed. M. parvicella, Type 0092, N. limicola, Type 0803 and Type 0041 were dominant in both conventional and biological nutrient removal activated sludge plants whereas the other Eikelboom's types of filaments dominated mostly in conventional activated sludge plants. The ability of foams to denitrify depended on the dominating tilamentous microorganism and type of substrate.     

In situ characterization of substrate uptake by Microthrix parvicella using microautoradiography

Microthrix parvicella is a filamentous microorganism responsible for bulking and foaming problems in many activated sludge treatment plants. The problems have increased with the introduction of nutrient removal in many countries, and presently, there is no reliable control strategy for M. parvicella. Little is known about the physiology of M. parvicella, and conflicting data exist about its preferred organic substrates, and whether it is able to be physiologically active under anaerobic and anoxic conditions. In this study, the ability of M. parvicella to take up various radioactively labeled organic compounds was investigated in situ at three nutrient removal plants using a microautoradiographic technique. Of 12 compounds tested under aerobic conditions only the long chain fatty acids (LCFA), oleic acid and palmitic acid, and to some extent a lipid, trioleic acid, were assimilated. None of the simple substrates such as acetate, propionate, butyrate, glucose, ethanol, glycine and leucine were taken up. Furthermore, the uptake of oleic acid was compared under anaerobic, anoxic and aerobic conditions, and it was demonstrated that in addition to aerobic conditions M. parvicella was also able to take up oleic acid under anaerobic and anoxic conditions. No difference in substrate uptake pattern for M. parvicella was found among the tested activated sludge plants. The results strongly indicate that a better control strategy against M. parvicella must rely on a better understanding of presence and availability of triglycerides and LCFA, and an improved knowledge of the physiology of M. parvicella under anaerobic and anoxic conditions.     

Influence of temperature and sludge loading on activated sludge settling,especially on Microthrix parvicella

During recent years modern full scale wastewater treatment plants with biological nitrification, denitrification and phosphorus removal have had increasing problems with foam formation on the surfaces of aerobic tanks and with bulking activated sludge. The results of a survey in 1995 (Kunst and Knoop, 1996) showed that most often the filamentous bacterium Microthrix parvicella is responsible for these problems. Up to today there is only little knowledge about its selection criteria in activated sludge. Therefore several expenments were done in full scale activated sludge plants and in laboratory systems under defined conditions to investigate the influence of low (< 0.1 kg/(kg·d)) and high (≤ 0.2 kg/(kg·d)) BOD₅-sludge loading rates on the growth and morphology of M. parvicella and the settlement of activated sludge. Furthermore the influence of temperatures of 5°C, 12°C and 20°C on the growth of M. parvicella was investigated. It was shown that M. parvicella grows at low BOD₅-sludge loading rate and low temperature and is the main causative organism of bulking and foaming sludge in nutrient removal plants. On the basis of this investigation it was concluded that the growth of M. parvicella and the settling problems of the activated sludge resulting from excessive growth of this filament will always appear in modern municipal wastewater treatment plants with BOD₅-sludge loading rate ≤ 0.1 kg/(kg·d) especially under low temperature conditions.     

Particle and micro-organism removal in conventional and advanced treatment technology

All international drinking water quality standards can be divided into four groups

• -(micro)biological: bacteria, viruses, cysts, higher organisms, etc.
• -toxicological: THM, AOX, pesticides, solvents, etc.
• -organoleptic (esthetic): taste, odor, color, turbidity, etc.
• -operational: DOC, AOC, pH, Ca²⁺, HCO₃⁻ , CI⁻, SO₄²⁻, etc.

The philosophy on drinking water treatment focuses on the removal of all the undesired species, dissolved and undissolved, available in raw water, in such a way that no new undesired compounds are introduced during treatment such as Al, Cl₂, THM, AOX and AOC or during distribution such as Pb, Cu, Cd and asbestos. Special attention is paid to the removal of organic and inorganic colloids and of micro-organisms. Microbiologically stable water during storage and distribution can be realized by removal of nutrients (DOC, AOC) without the use of chlorine of chlorine products.As an example the treatment systems of the Amsterdam Water Supply based on the relatively very polluted raw water of the river Rhine are described. For future expansion of the production capacity membrane processes such as hyperfiltration (HF), electrodialysis reversal (EDR) and ultrafiltration (UF) are investigated.Results are shown on conventional and advanced technology concerning: final water quality, natural and environmental protection, process stability and costs per m³.     

Foaming in anaerobic digesters caused by Microthrix parvicella

Three large wastewater treatment plants in the greater Stockholm area have experienced serious anaerobic digester foaming. Microscopic studies of the sludge from the foam phase showed a network of the filamentous organism Microthrix parvicella. The morphology of the long, coiled filament appeared to be affected by the anaerobic conditions where it became broken up into to shorter and thicker filaments. The operating strategy to prevent foam in the anaerobic digesters at these plants is to control the growth of M. parvicella in the activated sludge tanks by increasing the sludge load. Top installed stirrers and the addition of poly-aluminium salt have also been used to prevent foam formation.     

Evaluation of filamentous microorganism growth factors in an industrial wastewater activated sludge system

An investigation comprising four studies was undertaken to determine possible factors affecting the growth of several different types of filamentous microorganisms present in a bulking industrial wastewater activated sludge. Results from laboratory-scale continuous-flow and full-scale studies suggested that DO concentration and F:M ratio were the likely key factors affecting filamentous growth in the activated sludge. From the results of two laboratory studies isolating the effects of DO concentration and F:M ratio on filamentous growth, favorable growth ranges of DO concentration or F:M ratio were estimated for the following filaments: Microthrix parvicella, Nocardia spp., Nostocoida limicola II, and Types 0041, 1851, and 1863. Most of the bacteria causing filamentous bulking of the activated sludge were found to be filaments typically associated with low F:M, and increasing the F:M ratio appeared to cause N. limicola II to lose its competitive advantage in the activated sludge system. Type 1863, on the other hand, was found to be a low DO filament, as DO concentrations of 0.1 mg O₂/l or less appeared to be a necessary condition for its filamentous growth. Though Nocardia was found to be a low F:M filament, its growth also seemed to be affected by DO concentration, as its growth was stimulated by concentrations of 1.0 mg O₂/l or greater, with a near linear relationship up to at least 5 mg O₂/l.     

Identity, abundance and physiology of Aquaspirillum-related filamentous bacteria in activated sludge.

Microcolony-forming bacteria closely related to the genus Aquaspirillum in the Betaproteobacteria were recently observed to be abundant in many nutrient removal wastewater treatment plants. The developed oligonucleotide probe, Aqs997, however, occasionally also targeted some filamentous bacteria in activated sludge samples when fluorescence in situ hybridization was performed. In this study, the identity, abundance, and ecophysiology of these Aqs997-positive filamentous bacteria were studied in detail. Most of the Aqs997-positive filamentous bacteria could morphologically be identified as either Eikelboom Type 1701, Type 0041/0675 or possibly Type 1851, all characterized by epiphytic growth. They were found in almost all 21 wastewater treatment plants investigated. Two morphotypes were found. Type A filaments, which seemed to be the same genotype as the microcolony-forming bacteria targeted by probe Aqs997.Type B filaments also hybridized with probe GNS941, specific for the Chloroflexi phylum, so the true identity remains unclear. Aqs997-positive filaments usually stained Gram-negative, but Gram-positive filaments were also found, stressing the difficulties in identifying bacteria from morphology and simple staining results. Studies on the ecophysiology by microautoradiography showed that Aqs997-positive filamentous bacteria did not consume acetate and glucose, while some took up butyrate, mannose, and certain amino acids. Most likely, some Aqs997-positive filamentous bacteria were able to perform full denitrification such as the Aqs997-positive microcolony-forming bacteria, and some were able to store polyhydroxyalkanoates under anaerobic conditions, potentially being glycogen accumulating organisms.     

Causes of,and control strategies for,Microthrix parvicella bulking and foaming in nutrient removal activated sludge systems

Bench and pilot scale nutrient removal activated sludge units were used to examine the effect of factors such as temperature, substrate type (easily biodegradable in the form of acetate and slowly biodegradable in the form of oleic acid) on Microthrix parvicella growth. The configurations examined include complete mix with and without selectors (anoxic and anaerobic) and plug flow reactors. The results indicate that low temperatures and substrates in the form of long chain fatty acids favour the growth of M. parvicella. With respect to reactor configuration, a plug flow configuration was shown to be quite effective in controlling the growth of M. parvicella and producing a sludge with good settling characteristics, while the presence of a selector, either anoxic or anaerobic, had no significant effect on the growth of M. parvicella.     

Occurrence and control of filamentous bulking in aerated wastewater treatment plants of the French paper industry.

The occurrence of filamentous bacteria was investigated in 15 French pulp and paper activated sludge wastewater treatment plant (WWTP). Large filamentous populations were present in most of the plants. Identification carried out with conventional methods based on morphological features and staining techniques showed that the four main filamentous bacteria encountered in these industrial WWTP and responsible for bulking belong to the genera Thiothrix sp., Type 021 N, Haliscomenobacter hydrossis and Type 0092. During two years a specific survey was performed for three of these WWTP showing recurrent bulking phenomena. Data from WWTP performance, chemical data and filaments characterization were compared to correlate the presence of specific filaments with process operating conditions.     

Detection of filamentous and nitrifying bacteria in activated sludge with 16S rRNA probes

Activated sludge samples from wastewater treatment plants from potato starch and starch derivatives factory and from a municipal sewage treatment plant were analyzed with DNA probes specific for several filamentous bacteria. It was found that Haliscomenobacter hydrossis, Sphaerotilus natans, Thiothrix sp. and Eikelboom Type 021N were common in the activated sludges. Fluorescent in situ Hybridization (FISH) analysis could detect more types of sheathed bacteria and yielded a more accurate quantification of bacteria than conventional microscopy.In a pilot and a full scale wastewater treatment plant (WWTP) clear correlations were found between the SVI and growth of a Sphaerotilus natans and a Thiothrix sp. Addition of chlorine to the bulking sludge resulted in an improved SVI of the sludge but only damaged filamentous cells outside the floc. Nitrification was measured with substrate depletion and FISH analysis. Signal interpretation of FISH analysis was demonstrated both manually and with automated image analysis.     

Molecular biological methods to detect “Microthrix parvicella” and to determine its abundance in activated sludge

Molecular biological methods were evaluated in attempts to detect and quantitate levels of “Microthrix parvicella” in activated sludges. Approximately 66% of the 23S rRNA gene sequence of a strain (Ben43) of the Gram positive bulking and foaming organism “Microthrix parvicella” was determined, while a lesser amount was determined for “M. parvicella” strain RNI. The high mo1%G+C Gram positive bacteria (HGCGPBs) possess two powerfully diagnostic regions in the 23S rDNA and these were investigated in both strains. Firstly, the 18 nucleotide HGCGPB probe sequence (HGC69a) varied in at least two nucleotides with the sequence from both strains of “M. parvicella”. Secondly, an approximately 100 nucleotide stable insert between helices 54 and 55 in the 23S rRNA of HGCGPBs was discovered to be present in “M. parvicella”, but in both strains it was unique in length (79 nucleotides) and sequence. The region of the 23S rDNA with the stable insert was exploited to develop a polymerase chain reaction assay in which amplicons from “M. parvicella” were larger than those from nonHGCGPBs (i.e. all Bacteria except the HGCGPBs), and smaller than those from HGCGPBs. This assay was evaluated with DNAs extracted from activated sludges but although “M. parvicella” was morphologically identified, and was a dominant filament in at least one of the samples, no “M. parvicella” specific sized amplicons could be recovered from it. Amplicons of sizes generated by nonHGCGPBs and HGCGPBs were routinely produced in the stable insert PCR with DNAs from activated sludges where the highest yield was of amplicons from nonHGCGPBS.A second series of experiments were undertaken with the objective of evaluating the use of a non-radioactive hybridization method, based on extraction of bacterial RNA, for quantifying “M. parvicella” in activated sludge samples. Total nucleic acids were extracted from activated sludge samples and immobilized on nylon membranes. Probing with 16S rRNA-directed DIG-labelled oligonucleotide probes, detection of chemiluminescent signals on membranes and densitometry allowed hybridization signals to be quantified. The relationship between the amount of nucleic acid hybridized and the hybridization signal intensity observed was found to be linear over a specified range of signal intensities. A range of activated sludge samples were analysed for “M. parvicella” and variations in levels could be distinguished.     

城市污水处理厂的污泥膨胀研究分析

通过对北京市大型城市污水处理厂优势丝状菌鉴定及温度、生物选择器和溶解氧对污泥膨胀影响的研究分析,发现脱氮除磷工艺普遍会在冬季发生由Microthrix parvicella茵引起的污泥膨胀.研究了温度与SVI的变化规律,分析了出水亚硝酸氮和SVI的相关性,并对生物选择器和不同DO浓度对污泥膨胀的影响进行了分析.     

A new formula for turbulent-flow velocity and an explanation of A. P. Zegzhda’s experiments

1. The basic influence exerted by hydraulic grade, and, as a consequence, Froude number, on the value of the coefficient of hydraulic resistance is disclosed; this is reflected by formulas (16) and (18), and has found confirmation in field investigations [3], and in Zegzhda's experiments.
2. In the design of canals, the coefficient of hydraulic resistance should be determined by calculation as a function of the grade and dimensions of the flow, and not assigned as a function of the frequency with which the surface of the channel is treated.

     

Pilot remediation of sediment from the Petroleum harbour in Amsterdam

The Petroleum harbour project is the third pilot remediation, which was carried out within the framework of POSW (the national development programme for treatment processes of polluted sediments). The main objectives of the pilot remediation are:

• -to demonstrate the biological treatment of dredged materials on a practical scale;
• -to gain knowledge and experience for the future remediation of the total Petroleum harbour.

A strict tender procedure was carefully executed in order to select the most effective and ‘state of the art’ biodegradation technology. The selected remediation chain was a combination of 'standard' soil treatment technology and newly developed biotechnology. The contaminated sediments were separated by hydrocyclones, then the sand fraction was cleaned by froth flotation, and the fines were treated in a continuous flow reactor consisting of a cascade of 4 bioreactor tanks. A belt press was used for dewatering the fines. Dredging, biotechnological treatment and the effects of the remediation on the environment were monitored in detail. The quality of the treated sand fraction complied with the Dutch standards for re- use and was actually applied in a project of Rijkswaterstaat. Biodegradation resulted in a substantial decrease of the oil and PAH's contents, but due to the lack of breakdown of a few high-molecular PAH's, the quality requirements of the contract were not achieved. For less heavily polluted sediments and soils the applied biotechnology may be more effective. The results of the project show that biodegradation in bioreactors on a large scale is feasible. Furthermore useful information was gathered for the future remediation of the Petroleum harbour. It is concluded that the two main objectives of the project have been attained. Finally some recommendations for the future clean-up of the Petroleum harbour are given.     

Interactions between filamentous sulfur bacteria,sulfate reducing bacteria and poly-P accumulating bacteria in anaerobic-oxic activated sludge from a municipal plant

The interactions between filamentous sulfur bacteria (FSB), sulfate reducing bacteria (SRB) and poly-P accumulating bacteria (PAB) in the activated sludge of a municipal plant operated under anaerobic-oxic conditions were examined in batch experiments using return sludge (RAS) and settled sewage. Phosphate release and sulfate reduction occurred simultaneously under anaerobic conditions. SRB were more sensitive to temperature changes than PAB. SRB played an important role in the decomposition of propionate to acetate. When the sulfate reduction rates were high, there was a tendency for the maximum release of phosphate also to be high. This was explained by the fact that PAB utilized the acetate produced by SRB. Sulfur oxidizing bacteria were sensitive to temperature change. When the sulfate reduction rate was high, the sulfide oxidizing rate was also high and filamentous bulking occurred. The results showed that sulfate reduction was a cause of filamentous bulking due to Type 021N that could utilize reduced sulfur.     

Challenges to and Opportunities for Development of China's Water Resources in the 21st Century

ABSTRACT

The People's Republic of China is a developing country. Great achievements during the past 40 years have attracted worldwide attention, especially the fact that 22 per cent of the world population were sustained by only 7 per cent of the world's farmland. However the sustainable economic and social development of China is and will be facing serious challenges more critical than those that have happened in any part of the world. Water is a particular problem. The shortage of water that is almost inevitable in China is due to the following:

1. The heavy burden overpopulation places on development in the foreseeable future.

2. Compulsory development of irrigated agriculture as new reclaimable farmland is not adequate to satisfy increasing food demand.

3. The rapid' increase in water demand by industry that is now still in its initial stage.

4. Increase in domestic water demand due to growth of urban populations and improvement in their living standards.

5. Degradation of the water environment due to pollution, deforestation, soil erosion, overpumping of groundwater siltation of estuaries, salinization, and alkalization of farmland, desertification, etc.

6. Deficiencies in funding.

In spite of the serious situation mentioned above, opportunities for development of water resources in the 21st century do exist as follows:

1. Practice of water-saving strategies in the entire country, including industry, agriculture, and domestic life.

2. Coordination of economic development with water resources development; rational compositional structure of industry and agriculture; rational layout of the township system.

3. Implementation of large-scale inter-basin water transfer projects within the bearing capacity of natural environment.

4. Control of water pollution and improvement of the ecological environment.

5. Large-scale afforestation, as well as water and soil conservation works.

6. Better water resources management through legislative, technical, and educational measures, and through systematic training.

7. Control of overpopulation, which is of the utmost importance.

     

Evaluation of the impacts of model-based operation of SBRs on activated sludge microbial community.

Impact of model-based operation of nutrient removing SBRs on the stability of activated sludge population was studied in this contribution. The optimal operation scenario found by the systematic model-based optimisation protocol of Sin et al. (Wat. Sci. Tech., 2004, 50(10), 97-105) was applied to a pilot-scale SBR and observed to considerably improve the nutrient removal efficiency in the system. Further, the process dynamics was observed to change under the optimal operation scenario, e.g. the nitrite route prevailed and also filamentous bulking was provoked in the SBR system. At the microbial community level as monitored by DGGE, a transient shift was observed to gradually take place parallel to the shift into the optimal operation scenario. This implies that the model-based optimisation of a nutrient removing SBR causes changes at the microbial community level. This opens future perspectives to incorporate the valuable information from the molecular monitoring of activated sludge into the model-based optimisation methodologies. In this way, it is expected that model-based optimisation approaches will better cover complex and dynamic aspects of activated sludge systems.     

Performances of three R-AN-D-N wastewater treatment plants in the Czech Republic.

The evolution of Czech standards requires higher efficiency of nutrient removal from municipal wastewaters. At the beginning of the last decade of 20th century, a new activated sludge configuration called R-AN-D-N process has been described, successfully tested and now largely used at several wastewater treatment plants (WWTP) in the Czech republic. The main feature of the R-AN-D-N process is the introduction of a regeneration zone in sludge recycle, which enables to increase sludge age in the system without any substantial increase in WWTP volume. Performances of three Czech large WWTP with R-AN-D-N configuration have been monitored and compared within a period of one and a half years. The results confirmed excellent nutrient removal efficiency for wastewaters with different proportion between sewage and industrial effluents. Two of three monitored WWTP received wastewaters from breweries (Budweiser and Pilsner Urquell). The settleability of activated sludge from all three WWTP was correct, with SVI values usually ranging from 50 to 150 ml/g. Monitoring of sludge composition indicated proliferation of several filamentous bacteria, particularly types 0581, 0092 and M. parvicella. No severe bulking events were observed. Finally, the operational costs expressed in CZK (Czech crown: 1 CZK = [see symbol in text]0.0322) per cubic metre of treated sewage or per capita amounts respectively from 2.24 to 6.52, and from 285 to 342.     

Substrate utilization characteristics of the predominant filamentous and floc-forming bacteria isolated from a chemical fiber factory wastewater treatment plant

To supply theoretical verification of the function of a selector to control aerobic activated sludge bulking in the wastewater treatment plant for a chemical fiber factory in Taiwan, the filamentous and floc-forming bacteria in the aeration tank in the full-scale plant were examined microscopically and isolated. The kinetic characteristics of filamentous and floc-forming bacteria were also investigated.The predominant filamentous organism was Sphaerotilus natans. In addition to this organism, 21 strains of non-filamentous bacteria were isolated using the plate count method. These included Aeromonas jandaei DNA group 9, Acinetobacter johnsonii/genospecies 7, Bacillus pasteurii and Bacillus sp. (using the Biolog identification system). Nine strains showed the ability to form flocs when cultivated in glucose mineral salts medium.With glucose and acetate as sole substrates, the 4 floc-forming bacteria tested showed different substrate utilization characteristics. The 4 strains could be divided into 3 groups. The first group was the substrate degrading bacteria, the second group was the acid degrading bacteria and the other strains were those that had the highest substrate degradation rates at low substrate concentrations (below 800 mg/l). None of the floc-formers could utilize ethylene glycol, which is the major wastewater component. The kinetic characteristics of filamentous bacterium S. natans (Km = 4.0 mg glucose/l, Vm = 0.43 μl O₂/l) and the flocforming bacterium Aeromonas jandaei DNA group 9 (Km = 34.8 mg glucose/l, Vm = 0.59 μl O₂/l) provided information for selector design.     

Anaerobic processes in activated sludge

We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H₂S, O₂, NO₂₋ and NO₃₋. Denitriftcation and sulfate reduction rates were measured with ¹⁵N- and ³⁵S-tracer techniques. We showed that under normal reactor conditions (ca. 20% air saturation) anoxic zones develop within flocs allowing denitrification. The denitrtftcation rates amounted to 40% of the rates under anoxic conditions. At 100% air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20% air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport.Sulfate reduction was not detected in any of the sludges tested by microsensors or by tracer techniques even under anoxic conditions. This indicates that the sulfur cycle (sulfate reduction and sulfide oxidation) does not play a role in mineralization processes and bulking in activated sludge. Preliminary molecular work (in situ hybridization with the 16S-rRNA probe SRB385) indicated the presence of small amounts of sulfate reducing bacteria in all sludges. Either the probe is not specific or the sulfate reducers present are not active under reactor conditions.