Concentrations In Source Water Research Articles

Using spore removal to monitor plant performance for Cryptosporidium removal

Data from available literature indicate that Cryptosporidium oocysts are removed more efficiently than aerobic spore‐forming bacteria during water treatment processes involving clarification and filtration. Therefore, monitoring removal of naturally occurring aerobic spores can provide a conservative estimate of the potential for Cryptosporidium removal in full‐scale water treatment processes, which in turn can be used to establish the demonstration of performance credit allowed by the Long Term 2 Enhanced Surface Water Treatment Rule as well as to provide a valuable performance evaluation tool for water plant operators. The results from this study showed that (1) median raw water spore concentrations ranged from 300 to 3,000 spores/L for two lake sources and 80,000 to 400,000 spores/L for four river sources; (2) median filtered water spore concentrations rarely exceeded 5 spores/L, and these levels of removal were not apparently dependent on source water concentration; and (3) >4‐log spore removal could not be mathematically demonstrated unless raw water levels exceeded 10,000 spores/L (e.g., river sources).

Presence of Noroviruses and Other Enteric Viruses in Sewage and Surface Waters in The Netherlands

Since virus concentrations in drinking waters are generally below the detection limit, the infectious risk from drinking water consumption requires assessment from the virus concentrations in source waters and removal efficiency of treatment processes. In this study, we estimated from reverse transcription-PCR on 10-fold serially diluted RNA that noroviruses, the most prevalent waterborne gastroenteritis agents, were present at 4 (0.2 to 38) to 4,900 (303 to 4.6 x 10(4)) PCR-detectable units (PDU) per liter of river water (ranges are given in parentheses). These virus concentrations are still high compared with 896 to 7,499 PDU/liter of treated sewage and 5,111 to 850,000 PDU/liter in raw sewage. Sequencing analyses designated human norovirus GGII.4 Lordsdale as the most prevalent strain in the sampling period 1998 to 1999 in both sewage and surface waters. Other GGII strains were also very abundant, indicating that the majority of the virus contamination was derived from urban sewage, although very divergent strains and one animal strain were also detected in the surface and sewage waters. Rotaviruses were also detected in two large rivers (the Maas and the Waal) at 57 to 5,386 PDU/liter. The high virus concentrations determined by PCR may in part be explained by the detection of virus RNA instead of infectious particles. Indeed, reoviruses and enteroviruses that can be cultured were present at much lower levels, of 0.3 to 1 and 2 to 10 PFU/liter, respectively. Assuming 1% of the noroviruses and rotaviruses to be infectious, a much higher disease burden than for other viruses can be expected, not only because of the higher levels but also because of these viruses' higher infectivity and attack rates.

Discussion of silica speciation, fouling, control and maximum reduction

In the production of ultrapure water for the power and microelectronics industries, multiple pass reverse osmosis (RO) process is commonly the major step in the reduction of dissolved and suspended matter before polishing by ion exchange and other methods to attain the high purity requirements. With the diverse location of power plants and microelectronic manufacturing facilities around the world, silica concentrations in source waters can range between 1 and 60 ppm (mg/L) to even 300 ppm in some volcanic regions. High pressure steam generators and fine microelectronic structures now require water containing less than 1 ppb (ug/L) concentrations of silica. In designing purification processes, silica has presented issues not only as formidable challenges in many locations as RO membrane foulants, as well as a contaminant requiring efficient removal. Analyses of RO membrane foulants and correlation with water chemistry in the course of trouble-shooting numerous RO processes continues to offer us opportunities to understand silica chemistry, the patterns of silica fouling and methods by which we can chemically control the RO process. Such understanding is applicable to the operation of ion-exchange resin beds as well. In this paper we review the speciation of silica in feedwaters, and chemical approaches to controlling fouling and maximizing silica reduction. Silica and silicates are addressed in the three categories of reactive soluble, non-reactive soluble (colloidal, not filterable) and non-reactive insoluble (particulate, filterable) forms. A brief review of geochemistry, the chemical and biochemical dissolution and deposition of silica and silicates in nature is provided for insights and understanding of natural processes that can be applied to the task of process design and control in silica removal from water.

Controlling Giardia spp. and Cryptosporidium spp. in drinking water by microbial reduction processes

Drinking water microbial reduction has evolved from simple, effective chlorination to control waterborne diseases such as cholera and typhoid fever to advanced systems using ozone, chlorine dioxide, ultraviolet radiation, and combinations of disinfectants to control waterborne diseases such as poliomyelitis, hepatitis, giardiasis, and cryptosporidiosis. Giardia spp. and Cryptosporidium spp. have posed a major challenge to the water industry from a variety of perspectives. They occur in low concentrations in source waters, their infective doses in humans are low when compared with typical waterborne viruses and bacteria, they are difficult to inactivate with chlorine compounds, and they are difficult to determine if they are dead when detected in the environment or after microbial reduction in water treatment. However, Giardia spp. and Cryptosporidium spp. are readily controlled by ozone or ultraviolet radiation over a wide range of water-quality conditions. Chlorine dioxide provides a simple alternative to chlorine in some circumstances. Using modern microbial reduction process design techniques such as the integrated disinfection design framework (IDDF) ensures the provision of drinking water with a low risk of transmitting human pathogens to the consumer. Key words: ozone, chlorine dioxide, chlorine, ultraviolet, disinfection, microbial reduction, drinking water, Giardia, Cryptosporidium, parasite.

ControllingGiardiaspp. andCryptosporidiumspp. in drinking water by microbial reduction processes

Drinking water microbial reduction has evolved from simple, effective chlorination to control waterborne diseases such as cholera and typhoid fever to advanced systems using ozone, chlorine dioxide, ultraviolet radiation, and combinations of disinfectants to control waterborne diseases such as poliomyelitis, hepatitis, giardiasis, and cryptosporidiosis. Giardia spp. and Cryptosporidium spp. have posed a major challenge to the water industry from a variety of perspectives. They occur in low concentrations in source waters, their infective doses in humans are low when compared with typical waterborne viruses and bacteria, they are difficult to inactivate with chlorine compounds, and they are difficult to determine if they are dead when detected in the environment or after microbial reduction in water treatment. However, Giardia spp. and Cryptosporidium spp. are readily controlled by ozone or ultraviolet radiation over a wide range of water-quality conditions. Chlorine dioxide provides a simple alternative to chlorine in some circumstances. Using modern microbial reduction process design techniques such as the integrated disinfection design framework (IDDF) ensures the provision of drinking water with a low risk of transmitting human pathogens to the consumer.Key words: ozone, chlorine dioxide, chlorine, ultraviolet, disinfection, microbial reduction, drinking water, Giardia, Cryptosporidium, parasite.

A comparison of membrane softening on three South Florida groundwaters

This paper compares and contrasts the performance of one commercially-available softening membrane on surficial aquifer water at three different South Florida locations and the performance of two additional commercially-available softening membranes at one of the three South Florida locations. Data from pilot studies performed at each location along with established membrane performance equations were also used to develop a model which predicts the performance of membranes under differing operating conditions. In summary, the main findings of this investigation are: 1) The permeate water mass transfer coefficient was essentially the same for all three pilot locations and for the three membranes at the same location. This means that the pumping energy required to produce a certain permeate flow per a given amount of membrane area is similar for a full-scale membrane plant at each location. 2) The permeate salt concentration is a variable dependent on source water concentration and the salt mass transfer coefficient. For calcium, the mass transfer coefficient was different for only one of the membranes tested, so for the other two membranes the differences in source water calcium concentration governed the permeate calcium concentration. Other salts, such as chloride, had significantly different mass transfer coefficients, so the source water concentrations and the mass transfer coefficient both impacted the permeate salt concentration greatly. Also, as the permeate water flux is reduced for all the membranes, the permeate salt concentration increases since the salt flux does not vary with the variation in permeate water flux. 3) Membrane performance at different operating conditions than the piloted condition can be predicted using the established membrane performance equations, giving the full-scale membrane facility designer flexibility in the design of the membrane process.

The development and decline of phytoplankton blooms in the southern Benguela upwelling system. 1. Drogue movements, hydrography and bloom development

A drogue was placed in a patch of newly upwelled water on five different occasions between 1979 and 1981 in order to follow the temporal sequence of events after upwelling. The drogue moved over distances of 67 – 200 km within 4–7 days at mean speeds of 18–39 cm·s−1. Drogue movement was variable and generally in the direction of the prevailing wind. However, significant "up wind" movement occurred when the drogue was entrained in counter-currents. Variations in hydrographic parameters at the start of each sequence, and in the bottom mixed layer along the drogue tracks, indicate that upwelling source waters are not always uniform. However, nutrient concentrations in source water were high (mean concentrations for nitrate, silicate and phosphate were 20,8, 16,6 and 1,88 mmoln·m−3 respectively), whereas oxygen (4,0 dm3·m−3) and chlorophylls a (0,6 mg·m−3) concentrations were low. Once conditions stabilized, phytoplankton blooms developed rapidly in the upper layers, the cycle of bloom development and decline being completed in about 6–8 days. Nutrients decreased rapidly (and oxygen and chlorophyll a increased) with nitrates sometimes reaching concentrations of < 1 mmol·m−3, and oxygen and chlorophyll a peaking at concentrations of up to 9,8 dm3·m−3 and 21,2 mg·−3 respectively. Only once did light-limitation (due to deep mixing) influence bloom development. In this case, only moderately high chlorophyll a concentrations (∼ 10 mg·m−3) were attained. Bloom decline was usually associated with low nutrient concentrations and can be attributed mainly to sinking and dispersion of the phytoplankton, because zooplankton grazing appeared to have had an insignificant impact on the phytoplankton blooms.

Effectiveness of 1-bromo-3-chloro-5,5-dimethylhydantoin against Legionella pneumophila in a cooling tower.

Cooling towers are considered to be man-made amplifiers of Legionella spp. Thus, the proper maintenance and choice of biocides is important. The only biocidal measure that has thus far been shown to be effective in field tests is the judicious use of chlorination. Perturbation studies with 1-bromo-3-chloro-5, 5-dimethylhydantoin (Bromicide; Great Lakes Chemical Corp., West Lafayette, Ind.) (BCD) were conducted on an industrial cooling tower shown to contain Legionella pneumophila. At the concentrations recommended by the manufacturer, neither the density nor the activity of L. pneumophila was affected. At comcentrations greater than 2.0 ppm (2.0 micorgram/ml) free of residual, BCD was not effective in reducing L. pneumophila to source water concentrations, nor was it effective in reducing the 2-p-iodophenyl-3-p-nitrophenyl-5-phenyl tetrazolium chloride activity of the bacterium in situ. The data indicate that at concentrations up to 2.0 ppm, BCD is not effective in these tower studies.

A review of occurrences and treatment of polynuclear aromatic hydrocarbons in water

The scope of PAH contamination of raw, finished, and distributed waters is reviewed. The concentrations of PAHs in drinking water sources range from nanogram to microgram-per-liter quantities. Conventional treatment (flocculation, sedimentation, chlorination, and filtration) appears to substantially reduce total PAH concentrations present at higher concentrations in source waters. A major factor in this reduction is the removal of PAHs adsorbed onto particulate matter. The role of chlorination is not clear and reactions of PAHs with chlorine may in fact produce products which themselves are deleterious. Activated carbon can further assist in PAH removal. However, it may be inappropriate for treatment of PAHs present at low concentrations. Water entering the distribution system can become recontaminated via contact with reservoirs and pipes coated with coal-tar or asphalt based products.