Autotrophic denitrification using hydrogen oxidizing bacteria in continuous flow biofilm reactor

Autotrophic denitrification was investigated in five bench‐scale upflow attached growth reactors using hydrogen oxidizing bacteria under anoxic conditions. The performance of sand, granular activated carbon (GAC), crushed pumice, crushed volcanic rock, and plastic media were evaluated as the support material. The reactors were inoculated with acclimated cultures obtained from domestic sewage treatment plant. A synthetic solution containing nitrate was used as the influent. The reactor performance was evaluated by measuring influent and effluent nitrate concentration. The design parameters demonstrated that the effectiveness of autotrophic denitrification is comparable to that of the heterotrophic process and may be utilized economically for drinking water treatment either as the main process or as a supplemental process for ion exchange regenerant treatment.     

Biomass of suspended bacteria over coral reefs

The biomass of bacteria suspended in water flowing over coral reefs at Lizard Island and Yonge Reef (Northern Great Barrier Reef) was estimated by measurement of muramic acid. Values ranged from 20 mg C m^-3 in the open water up to about 60 mg C m^-3 over the reef flat. Direct counts of total numbers of free bacteria were made for comparison. Values of around 2.0x10⁹ cells g^-1 muramic acid showed that there was a good agreement between direct counts and muramic acid content of free bacteria in the open water. In samples containing suspended particulate matter, ratios of direct counts to muramic acid concentration were lower, because bacteria on particles could not be counted. Thus, these ratios were used to indicate the proportions of bacteria attached to particles. Changes in the biomass and numbers of bacteria were determined in water masses identified either by a drogue or fluorescein, as they moved across the reefs. In the zone on the outside of the reef, the number of free bacteria decreased compared to open sea water, but total biomass increased, showing that particulate matter containing bacteria was thrown up into suspension. About 50% of bacteria were attached to particles. Water flowing over the reef flats contained much particulate material with bacteria attached. Bacteria constituted between about 5 and 20% of particulate organic carbon.     

Characteristics and removal mechanism of the precursors of N-chloro-2,2-dichloroacetamide in a drinking water treatment process at Taihu Lake

• N-Cl-DCAM, an emerging N-DBP in drinking water was investigated. • A new BAC has a better removal efficiency for N-Cl-DCAM precursors than an old BAC. • N-Cl-DCAM precursors are more of low molecular weight and non-polar. • Adsorption of GAC plays a major role in removal of N-Cl-DCAM precursors by an O₃-BAC. N-chloro-2,2-dichloroacetamide (N-Cl-DCAM) is an emerging nitrogenous disinfection by-product (N-DBP) which can occur in drinking water. In this study, an analytical method based on liquid chromatography with tandem mass spectrometry (LC-MS/MS) was developed to validate the concentration of N-Cl-DCAM, which was found to be 1.5 mg/L in the effluent of a waterworks receiving raw water from Taihu Lake, China. The changes of N-Cl-DCAM formation potential (N-Cl-DCAMFP) in the drinking water treatment process and the removal efficiency of its precursors in each unit were evaluated. Non-polar organics accounted for the majority of N-Cl-DCAM precursors, accounting for 70% of the N-Cl-DCAM FP. The effect of conventional water treatment processes on the removal of N-Cl-DCAM precursors was found to be unsatisfactory due to their poor performance in the removal of low molecular weight (MW) or non-polar organics. In the ozonation integrated with biological activated carbon (O₃-BAC) process, the ozonation had little influence on the decrease of N-Cl-DCAM FP. The removal efficiency of precursors by a new BAC filter, in which the granular activated carbon (GAC) had only been used for four months was higher than that achieved by an old BAC filter in which the GAC had been used for two years. The different removal efficiencies of precursors were mainly due to the different adsorption capacities of GAC for individual precursors. Low MW or non-polar organics were predominantly removed by GAC, rather than biodegradation by microorganisms attached to GAC particles.     

Comparison of membrane fouling in ultrafiltration of down-flow and up-flow biological activated carbon effluents

The UF membrane fouling by down- and up-flow BAC effluents were compared. Up-flow BAC effluent fouled the membrane faster than down-flow BAC effluent. The combined effects dominated irreversible fouling. The extent of fouling exacerbated by inorganic particles was higher. The TMP, permeate flux, and normalized membrane flux during 21 days of UF of DBAC and UBAC effluents. Fouling during ultrafiltration of down- and up-flow biological activated carbon effluents was investigated to determine the roles of polysaccharides, proteins, and inorganic particles in ultrafiltration membrane fouling. During ultrafiltration of down- flow biological activated carbon effluent, the trans-membrane pressure was≤26 kPa and the permeate flux was steady at 46.7 L?m⁻²?h⁻¹. However, during ultrafiltration of up-flow biological activated carbon effluent, the highest trans-membrane pressure was almost 40 kPa and the permeate flux continuously decreased to 30 L?m⁻²?h⁻¹. At the end of the filtration period, the normalized membrane fluxes were 0.88 and 0.62 for down- and up-flow biological activated carbon effluents, respectively. The membrane removed the turbidity and polysaccharides content by 47.4% and 30.2% in down- flow biological activated effluent and 82.5% and 22.4% in up-flow biological activated carbon effluent, respectively, but retained few proteins. The retention of polysaccharides was higher on the membrane that filtered the down- flow biological activated effluent compared with that on the membrane that filtered the up-flow biological activated carbon effluent. The polysaccharides on the membranes fouled by up-flow biological activated carbon and down- flow biological activated effluents were spread continuously and clustered, respectively. These demonstrated that the up-flow biological activated carbon effluent fouled the membrane faster. Membrane fouling was associated with a portion of the polysaccharides (not the proteins) and inorganic particles in the feed water. When there was little difference in the polysaccharide concentrations between the feed waters, the fouling extent was exacerbated more by inorganic particles than by polysaccharides.     

Bacteriological analysis of a pond water from Gobardanga,West Bengal

The present communication deals with the bacteriological examination of a pond water, which is being used as one of the sources of drinking water, by multiple tube fermentation test to detect the coliform bacteria. The test was performed sequentially in three stages: presumptive, confirmed and completed coliform test. The results show that as the most probable number (MPN) index per 100 ml is 23, that pond water should be treated as nonpotable.     

Presence,dissemination and removal of antibiotic resistant bacteria and antibiotic resistance genes in urban drinking water system: A review

Reviewed the change of ARGs and ARB in full-scale urban drinking water systems. Conventional processes are more promising than BAC process in ARGs removal. Mechanisms of ARGs enrichment and spread in BAC filter and DWDSs are discussed. Raise the need of future research on ARGs and ARB change in building plumbing systems. Antibiotic resistance in aquatic environment has become an important pollution problem worldwide. In recent years, much attention was paid to antibiotic resistance in urban drinking water systems due to its close relationship with the biosafety of drinking water. This review was focused on the mechanisms of antibiotic resistance, as well as the presence, dissemination and removal of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the urban drinking water system. First, the presence of ARB and ARGs in the drinking water source was discussed. The variation of concentration of ARGs and ARB during coagulation, sedimentation and filtration process were provided subsequently, in which filtration was proved to be a promising technology to remove ARGs. However, biological activated carbon (BAC) process and drinking water distribution systems (DWDSs) could be incubators which promote the antibiotic resistance, due to the enrichment of ARGs and ARB in the biofilms attached to the active carbon and pipe wall. Besides, as for disinfection process, mechanisms of the inactivation of ARB and the promotion of conjugative transfer of ARGs under chlorine, ozone and UV disinfection were described in detail. Here we provide some theoretical support for future researches which aim at antibiotic resistance controlling in drinking water.     

Change in a bacterial population during the process of degradation of a phytoplankton bloom in a brackish lake

Change in a bacterial population during the process of degradation of a phytoplankton bloom was investigated at Lake Hamana, Japan in June 1981. The predominant phytoplankton were Prorocentrum micans Ehrenberg and P. triestinum Schiller. While most phytoplankton cells were living and moving actively, most bacteria were those in a free-living state (free-living bacteria) and the number of bacteria associated with particulate materials (attached bacteria) was less than a few percent of the total bacterial number. As the decline process proceeded, the number of free-living bacteria remained almost constant or decreased slightly; on the other hand, the number of attached bacteria increased gradually and reached about 40% of the total bacterial number. These results indicate that some of the free-living bacteria become attached to particulate organic matter and grow on the surface of the particles.     

Impact of total organic carbon and chlorine to ammonia ratio on nitrification in a bench-scale drinking water distribution system

Nitrification occurs in chloraminated drinking water systems and is affected by water quality parameters. The aim of this study was to investigate the impact of total organic carbon and chlorine to ammonia ratio on nitrification potential in a simulated drinking water distribution system as during chloramination. The occurrence of nitrification and activity of nitrifying bacteria was primarily monitored using four rotating annular bioreactors (RAB) with different chlorine to ammonia ratios and total organic carbon (TOC) levels. The results indicated that nitrification occurred despite at a low influent concentration of ammonia, and a high concentration of nitrite nitrogen was detected in the effluent. The study illustrated that reactors 1(R1) and 3 (R3), with higher TOC levels, produced more nitrite nitrogen, which was consistent with the ammonia-oxidizing bacteria (AOB) counts, and was linked to a relatively more rapid decay of chloramines in comparison to their counterparts (R2 and R4). The AOB and HPC counts were correlated during the biofilm formation with the establishment of nitrification. Biofilm AOB abundance was also higher in the high TOC reactors compared with the low TOC reactors. The chlorine to ammonia ratio did not have a significant impact on the occurrence of nitrification. Bulk water with a high TOC level supported the occurrence of nitrification, and AOB development occurred at all examined chlorine to ammonia dose ratios (3:1 or 5:1).     

Seasonal and treatment-process variations in invertebrates in drinking water treatment plants

• Seasonal and treatment-process variations in invertebrates in a DWTP were analyzed. • The propagation and leakage of invertebrates in BAC filter were the most serious. • Invertebrates can survive and reproduce in chlorine disinfected clear water tanks. • Proportions of endogenous invertebrates increased along the treatment process. Problems associated with excessive propagation and leakage of invertebrates in drinking water have received increasing attention in recent years. We performed a monthly survey of invertebrate abundance and taxa in the effluent of each treatment stage in a drinking water treatment plant between May 2015 and April 2016 and analyzed seasonal and treatment-process variations in invertebrates. The results showed that invertebrate abundances in raw water, effluent of the biological activated carbon (BAC) filter, and finished water significantly correlated with water temperature, whereas no correlation was observed between water temperature and invertebrate abundance in the effluents of the sedimentation tank and sand filter. The dominant taxa in the effluent of each treatment stage were rotifers, nematodes, and crustaceans. The sedimentation tank could efficiently remove invertebrates with an annual average removal rate of 92%. The propagation and leakage of invertebrates occurred in the sand and BAC filters but more seriously in the latter. The average reproduction rate in the BAC filter was 268.8% with rotifers as the taxon that leaked the most. Invertebrate survival and reproduction were also observed in the chlorine-disinfected clean water reservoir with an average reproduction rate of 41.9%. Owing to differences in chlorine resistance, the reproduction ability of the dominant taxa was in the order nematodes>crustaceans>rotifers. The proportion of endogenous invertebrates gradually increased along the treatment process. The average proportion of endogenous invertebrates in the finished water was higher than 79.0%. Our findings suggested that waterworks should pay more attention to endogenous invertebrate growth.     

What have we known so far about microplastics in drinking water treatment? A timely review

• 23 available research articles on MPs in drinking water treatment are reviewed. • The effects of treatment conditions and MP properties on MP removal are discussed. • DWTPs with more steps generally are more effective in removing MPs. • Smaller MPs (e.g.,<10 μm) are more challenging in drinking water treatment. Microplastics (MPs) have been widely detected in drinking water sources and tap water, raising the concern of the effectiveness of drinking water treatment plants (DWTPs) in protecting the public from exposure to MPs through drinking water. We collected and analyzed the available research articles up to August 2021 on MPs in drinking water treatment (DWT), including laboratory- and full-scale studies. This article summarizes the major MP compositions (materials, sizes, shapes, and concentrations) in drinking water sources, and critically reviews the removal efficiency and impacts of MPs in various drinking water treatment processes. The discussed drinking water treatment processes include coagulation-flocculation (CF), membrane filtration, sand filtration, and granular activated carbon (GAC) filtration. Current DWT processes that are purposed for particle removal are generally effective in reducing MPs in water. Various influential factors to MP removal are discussed, such as coagulant type and dose, MP material, shape and size, and water quality. It is anticipated that better MP removal can be achieved by optimizing the treatment conditions. Moreover, the article framed the major challenges and future research directions on MPs and nanoplastics (NPs) in DWT.     

Assessment of antibiotic resistance genes in dialysis water treatment processes

• Quantitative global ARGs profile in dialysis water was investigated. • Totally 35 ARGs were found in the dialysis treatment train. • 29 ARGs (highest) were found in carbon filtration effluent. • erm and mtrD-02 occurred in the final effluent. • The effluent was associated with health risks even after RO treatment. Dialysis water is directly related to the safety of hemodialysis patients, thus its quality is generally ensured by a stepwise water purification cascade. To study the effect of water treatment on the presence of antibiotic resistance genes (ARGs) in dialysis water, this study used propidium monoazide (PMA) in conjunction with high throughput quantitative PCR to analyze the diversity and abundance of ARGs found in viable bacteria from water having undergone various water treatment processes. The results indicated the presence of 35 ARGs in the effluents from the different water treatment steps. Twenty-nine ARGs were found in viable bacteria from the effluent following carbon filtration, the highest among all of the treatment processes, and at 6.96 Log (copies/L) the absolute abundance of the cphA gene was the highest. Two resistance genes, erm (36) and mtrD-02, which belong to the resistance categories macrolides-lincosamides-streptogramin B (MLSB) and other/efflux pump, respectively, were detected in the effluent following reverse osmosis treatment. Both of these genes have demonstrated the potential for horizontal gene transfer. These results indicated that the treated effluent from reverse osmosis, the final treatment step in dialysis-water production, was associated with potential health risks.     

Bacteriological quality assessment of drinking water available at the flood affected areas of Peshawar

Monsoon flooding occurred in the main areas of the Khyber Pakhtunkhwa, Punjab, and Balochistan as well as parts of Gilgit Baltistan of Pakistan and Azad Jammu Kashmir in July 2010. Water-borne diseases such as cholera, enteric fever, and dysentery were common among the inhabitants of flood-affected areas which were selected for sample collection. In the present study, 10 sites in District Peshawar were selected and drinking water samples collected. These samples were analyzed for the total plate count (TPC), total coliform bacteria (TCB), total fecal coliform bacteria (TFCB), Escherichia coli (EC), Pseudomonas aeruginosa (PA), Vibrio cholerae (VB), Salmonella Shigella, and Staphylococcus aureus. The TPC ranged from 8 × 10¹ to 7 × 10⁴ CFU/ml. The TCB ranged from <1.1 to 280 MPN/100 ml. Twenty percent of the samples were contaminated with TFCB, EC, Salmonella, Shigella, and Staphylococcus aureus, while only one sample contaminated with PA. Forty percent of the samples were contaminated with VB. The surface and well water was greatly contaminated by flooding and major improvements on priority basis are essential.     

Effect of biological activated carbon filter depth and backwashing process on transformation of biofilm community

We studied BAC biofilm during the process of initial operation and backwash. Microbial diversity decreased gradually with the increase of BAC filter depth. Proteobacteria dominated at the phylum level among the BAC biofilm samples. α-proteobacteria increased about 10% in all carbon filter depth after backwash. The biological activated carbon (BAC) is a popular advanced water treatment to the provision of safe water supply. A bench-scale device was designed to gain a better insight into microbial diversity and community structure of BAC biofilm by using high-throughput sequencing method. Both samples of BAC biofilm (the first, third and fifth month) and water (inlet water and outlet water of carbon filter, outlet water of backwashing) were analyzed to evaluate the impact of carbon filter depth, running time and backwash process. The results showed that the microbial diversity of biofilm decreased generally with the increase of carbon filter depth and biofilm reached a steady-state at the top layer of BAC after three months’ running. Proteobacteria (71.02%–95.61%) was found to be dominant bacteria both in biofilms and water samples. As one of opportunistic pathogen, the Pseudomonas aeruginosa in the outlet water of device (1.20%) was about eight times higher than that in the inlet water of device (0.16%) at the genus level after five-month operation. To maintain the safety of drinking water, the backwash used in this test could significantly remove Sphingobacteria (from 8.69% to 5.09%, p<0.05) of carbon biofilm. After backwashing, the operational taxonomic units (OTUs) number and the Shannon index decreased significantly (p<0.05) at the bottom of carbon column and we found the Proteobacteria increased by about 10% in all biofilm samples from different filter depth. This study reveals the transformation of BAC biofilm with the impact of running time and backwashing.     

Prototype design for a closed marine system employing quarternary water processing

A small 2, 271-1 (600-gallon) prototype recirculating marine water system was designed and evaluated (26 months). The system employed a quaternary (mechanical, algal, bacterial and chemical) series of processing units with the aim of achieving long-term seawater quality and constancy without water replacement. Total ammonia (0.05±0.005 ppm), un-ionized ammonia (0.0036±0.0003 ppm), nitrite (0.10±0.014 ppm), nitrate (24.6±2.0 ppm), phosphate (14.0±2.1 ppm), dissolved oxygen (6.5–7.2 mg/l) and pH (7.80 to 8.25) were maintained at acceptable levels for the entire period. The biomass load (1.82 kg/397 l) consisted of 4 nurse sharks which were fed ad-lib twice a week. Further, low levels of total bacteria (1.5×102 bacteria/ml) and coliforms [most probable number (MPN) index 17/dl] were present in the seawater. The system design is suggested for use in laboratory and mariculture installations.     

Feeding of Pseudocalanus minutus on living and non-living particles

A seasonal study of carbon content of living and of carbon and nitrogen content of non-living particulate material in seawater is presented. Grazing by Pseudocalanus minutus on living and non-living particles has been investigated over 1 year. Seasonal variations in the food uptake were associated with seasonal variations of each chemical component of the particles in the water. The amount of non-living carbon constituted the major part of the food ingested, irrespective of season. The ingested living carbon always accounted for a small fraction of the total copepod body carbon. The proportion of living carbon ingested could be equivalent to or even higher than non-living carbon at times during the late spring, summer and fall. The concentration of both living and non-living material within each particle peak of the spectra in the water seemed to affect the balance between non-living and living particle uptake. Non-living particles cannot be considered only as a supplementary food source for small copepods; they are a basic food for P. minutus at all times.     

Influences of Suspended Particles on the Runoff of Pesticides from an Agricultural Field at Askim, SE-Norway

Field and laboratory experiments were conducted to study the loss of particles from agricultural fields, and the role of suspended particles in carrying pesticides in surface runoff and drainage water. Propiconazole, a widely used fungicide was applied to experimental fields located at Askim, SE-Norway. Samples from surface runoff and drainage water were collected and analyzed for sediment mass, pesticides, particulate and dissolved organic carbon through a whole year. The surface soil and the runoff material were characterized by its particle size distribution, organic carbon content in size fractions and its ability to bind propiconazole. The results show that (1) particle runoff mostly occurred during the rainfall event shortly after harrowing in autumn. The highest particle concentration observed in the surface runoff water was 4600 mg l^–1, and in the drainage water 1130 mg l^–1; (2) the erosion of surface soil is size selective. The runoff sediment contained finer particle/aggregates rich in organic matter compared to its original surface soil; (3) the distribution coefficient (K _d) of propiconazole was significantly higher in the runoff sediment than in the parent soil. According to our calculation, particle-bound propiconazole can represent up to 23% of the total amount of propiconazole in a water sample with a sediment concentration of 7600 mg l^–1, which will significantly influence the transport behavior of the pesticide.     

Seasonal variations in abundance of nitrifying bacteria in fish pond ecosystem

Seasonal changes in abundance of nitrifiers (ammonia-oxidizing and nitrite-oxidizing bacteria) in surface and bottom water of freshwater ponds were examined with respect to temperature, DO, pH as well as concentration of ammonia and nitrite. The most probable number (MPN) of ammonia-oxidizers in different ponds varied from 1297 +/- 3.6 to 1673.23 +/- 0.36 ml(-1) in bottom and 720.5 +/- 8.1 to 955.3 +/- 10.8 ml(-1) in surface water during the rainy season while the MPN ranged from 1074 +/- 1.07 to 1372.17 +/- 4.6 ml(-1) in bottom and 515 +/- 10.1 to 678 +/- 11.8 ml(-1) in surface water in winter. However, the MPN were greatly reduced in summer and ranged from 435.05 +/- 15.7 to 547.54 +/- 2.12 ml(-1) in bottom and 218.7 +/- 7.3 to 368.4 +/- 9.32 ml(-1) in surface water. Similar seasonal trends were also observed in MPN of nitrite-oxidizers. Among all the physico-chemical parameters, abundance of nitrifiers was more positively correlated with ammonia and nitrite concentration in all the seasons. The abundance of nitrifiers in surface and bottom water was highest in rainy season followed by winter and modest in summer. The potential nitrification activities and oxidation rates were shown to be linear and activity of ammonia-oxidizing and nitrite-oxidizing bacteria was highest during rainy season.     

Effects of metal pollution in the monosodium glutamate production effluent on full exploitation and biological treatment

Monosodium glutamate (MSG) effluent was sampled from three MSG mills and 21 metal elements were measured with a inductively coupled plasma (ICP) Spectrometer. The total metal concentration of each MSG wastewater sample was 19192, 3190 and 3161 mg/L respectively. Compared with the water quality standard issued by the Chinese Government and the World Health Organization (WHO), some values were found to exceed the standards. The 24hr‐LC₅₀, 48hr‐LC₅₀, 72hr‐LC₅₀ and 96hr‐LC₅₀ to the fish Ctenopharyngodon idellus were 6.9%, 3.2%, 2.5% and 1.4% MSG wastewater individually. The specific growth rate for photosynthetic bacteria (PSB) Rhodopseudomonas sphaeroides was inhibited by the metals in MSG wastewater. Therefor the MSG wastewater should not be discharged into drinking, irrigation and fishery water systems, moreover it cannot be treated by general biological processes efficiently. How to develop an effective biotechnique for the utilization of organic pollutants in MSG effluent will also be discussed in this paper.     

Influences of suspended particles on the runoff of pesticides from an agricultural field at Askim, SE-Norway

Field and laboratory experiments were conducted to study the loss of particles from agricultural fields, and the role of suspended particles in carrying pesticides in surface runoff and drainage water. Propiconazole, a widely used fungicide was applied to experimental fields located at Askim, SE-Norway. Samples from surface runoff and drainage water were collected and analyzed for sediment mass, pesticides, particulate and dissolved organic carbon through a whole year. The surface soil and the runoff material were characterized by its particle size distribution, organic carbon content in size fractions and its ability to bind propiconazole. The results show that (1) particle runoff mostly occurred during the rainfall event shortly after harrowing in autumn. The highest particle concentration observed in the surface runoff water was 4600 mg l(-1), and in the drainage water 1130 mg l(-1); (2) the erosion of surface soil is size selective. The runoff sediment contained finer particle/aggregates rich in organic matter compared to its original surface soil; (3) the distribution coefficient (Kd) of propiconazole was significantly higher in the runoff sediment than in the parent soil. According to our calculation, particle-bound propiconazole can represent up to 23% of the total amount of propiconazole in a water sample with a sediment concentration of 7600 mg l(-1), which will significantly influence the transport behavior of the pesticide.     

恩诺沙星对土壤细菌数量及微生物生物量碳的影响

为了评价兽药恩诺沙星(Enrofloxacin,ENR)对土壤微生物的影响,采用平板计数法和熏蒸浸提法研究了不同含量恩诺沙星(wENR)对土壤细菌数量和土壤微生物生物量碳(MBC)含量的影响.结果发现,添加药物组细菌数量和土壤微生物生物量碳含量均低于对照组,且药物含量越高,细菌数量和土壤微生物生物量碳含量越低;较低含量的恩诺沙星(wENR<0.1μg·g-1,细菌数量;wENR<1μg·g-1,MBC)对细菌数量和微生物生物量碳含量影响不显著(与对照组比较,p>0.05),而较高含量的恩诺沙星(wENR≥0.1μg·g-1,细菌数量;wENR≥1μg·g-1,MBC)则影响显著(与对照组比较,p<0.05).以上结果表明恩诺沙星残留可显著影响土壤细菌数量和微生物生物量碳含量,进而可能影响土壤特性和土壤的一些生态过程。