The geographic distribution of fluoride in surface and groundwater in Ethiopia with an emphasis on the Rift Valley

This paper analyzes the most extensive database on fluoride distribution in Ethiopia. Of the total 1438 water samples tested, 24.2% had fluoride concentrations above the 1.5 mg/l recommended optimum concentration recommended by WHO. Regionally, by far the highest fluoride levels were recorded in the Rift Valley, where 41.2% of all samples exceeded the 1.5 mg/l level. Only 1.0% of the samples from the central and northwestern highlands and 10.0% in the southeastern highlands exceeded 1.5 mg/l. Larger proportions of deep wells (50.0%) and hot springs (90.0%) than shallow wells (27.2%) and cold springs (12.6%) exceeded the 1.5 mg/l level. The highest fluoride concentrations were recorded for Rift Valley lakes Shala (264.0 mg/l) and Abijata (202.4 mg/l) and the lowest in Lake Tana, and rivers, wells and springs in the highlands. The fluoride concentrations of the Awash River, which originates in the highlands and flows through the Rift Valley, increase downstream, giving concern over the current diversion of high-fluoride water from Lake Beseka. Of the various flourosis prevention methods tried in Ethiopia, the treatment of surface water has been shown to be the most feasible and effective for towns and large commercial farms in the Rift Valley, although defluoridation methods should be considered for smaller rural communities.     

Groundwater quality impacts from the land application of treated municipal wastewater in a large karstic spring basin: Chemical and microbiological indicators

Geochemical and microbiological techniques were used to assess water-quality impacts from the land application of treated municipal wastewater in the karstic Wakulla Springs basin in northern Florida. Nitrate-N concentrations have increased from about 0.2 to as high as 1.1 mg/L (milligrams per liter) during the past 30 years in Wakulla Springs, a regional discharge point for groundwater (mean flow about 11.3 m³/s) from the Upper Floridan aquifer (UFA). A major source of nitrate to the UFA is the approximately 64 million L/d (liters per day) of treated municipal wastewater applied at a 774 ha (hectare) sprayfield farming operation. About 260 chemical and microbiological indicators were analyzed in water samples from the sprayfield effluent reservoir, wells upgradient from the sprayfield, and from 21 downgradient wells and springs to assess the movement of contaminants into the UFA. Concentrations of nitrate-N, boron, chloride, were elevated in water samples from the sprayfield effluent reservoir and in monitoring wells at the sprayfield boundary. Mixing of sprayfield effluent water was indicated by a systematic decrease in concentrations of these constituents with distance downgradient from the sprayfield, with about a 10-fold dilution at Wakulla Springs, about 15 km (kilometers) downgradient from the sprayfield. Groundwater with elevated chloride and boron concentrations in wells downgradient from the sprayfield and in Wakulla Springs had similar nitrate isotopic signatures, whereas the nitrate isotopic composition of water from other sites was consistent with inorganic fertilizers or denitrification. The sprayfield operation was highly effective in removing most studied organic wastewater and pharmaceutical compounds and microbial indicators. Carbamazepine (an anti-convulsant drug) was the only pharmaceutical compound detected in groundwater from two sprayfield monitoring wells (1-2 ppt). One other detection of carbamazepine was found in a distant well water sample where enteroviruses also were detected, indicating a likely influence from a nearby septic tank.     

Experimental Assessment of Rates of Nitrate Removal by River Bed Sediments

C oncentrations OF C hloride , nitrate-N, sulphate, sodium, ammoniacal-N and potassium were monitored for six days in 20 riverine sediment-water flow tank experiments. Only nitrate-N and ammonical-N showed consistent patterns over a period of time. Nitrate-removal rates ranged from −15 mg N/m².d (coarse material) to +49 mg N/m².d (fine sediment) when the initial concentration of nitrate-N was 2 mg/1. An increase in initial concentration to 11 mg/1 produced corresponding removal rates of 67–241 mg N/m².d. Likely removal mechanisms are discussed. The results suggest management possibilities for stream bed ecosystems and raw water impoundments with respect to nitrogen cycling.     

Enhanced in situ denitrification for a municipal well

In 37% of small community systems in Nebraska at least one sample exceeded the drinking water standard for nitrate of 10 mg N L(-1) during the period from 1982 to 1998 (US Bureau of Reclamation, US Department of the Interior, 1999). In this experiment a daisy well system was designed to promote denitrification in the radial capture zone of a municipal well with nitrate-N levels> 10mg L(-1), and thereby bring the nitrate concentration into compliance. The remediation design consisted of eight 15 cm diameter outer perimeter reduction wells and eight 5 cm diameter inner perimeter oxidation wells which are located roughly 18 and 9 m, respectively, from the municipal well, which serves as the extraction well. Endemic microbes are stimulated by pulsing separate injections of acetate-C and nitrate contaminated water (C:N = 1.2) to enhance denitrification in the capture zone. Water was extracted from the municipal well at 6.6 L s(-1) (liters per second). A 45% nitrate reduction occurred in municipal well samples when the total acetate-C input was increased by lengthening the acetate pulse from 1.0 to 1.5 h (C:N=1.8). Nitrate concentration stabilized at about 6.3 mg NO3-N L(-1) for two weeks during alternating acetate pulse lengths. The in situ denitrification process was sustained for three months without evidence of clogging. Results from this experiment indicated that the extracted water was in compliance with respect to nitrate, nitrite, trihalomethanes, turbidity, and total and fecal coliforms; however, the total plate count exceeded the maximum permissible limit (500 cfu/mL).     

Drinking water quality in the Ethiopian section of the East African Rift Valley I--data and health aspects

Drinking water samples were collected throughout the Ethiopian part of the Rift Valley, separated into water drawn from deep wells (deeper than 60 m), shallow wells (<60 m deep), hot springs (T>36 degrees C), springs (T<32 degrees C) and rivers. A total of 138 samples were analysed for 70 parameters (Ag, Al, As, B, Ba, Be, Bi, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Cu, Dy, Er, Eu, F, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, NO(2), NO(3), Pb, Pr, Rb, Sb, Se, Si, Sm, Sn, SO(4), Sr, Ta, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn, Zr, temperature, pH, conductivity and alkalinity) with ion chromatography (anions), spectrometry (ICP-OES and ICP-MS, cations) and parameter-specific (e.g. titration) techniques. In terms of European water directives and WHO guidelines, 86% of all wells yield water that fails to pass the quality standards set for drinking water. The most problematic element is fluoride (F), for which 33% of all samples returned values above 1.5 mg/l and up to 11.6 mg/l. The incidence of dental and skeletal fluorosis is well documented in the Rift Valley. Another problematic element may be uranium (U)-47% of all wells yield water with concentrations above the newly suggested WHO maximum acceptable concentration (MAC) of 2 microg/l. Fortunately, only 7% of the collected samples are above the 10 microg/l EU-MAC for As in drinking water.     

Environmental and nutritional factors affecting geosmin synthesis by Anabaena sp

A cyanobacterium isolated from a source-water reservoir during a spring odor and taste episode and identified as Anabaena sp. consistently produced geosmin during laboratory culture on modified BG-11 liquid medium. Maximal geosmin/biomass occurred at 20 degrees C and a light intensity of 17 microE/m2/s; geosmin/chla values directly correlated with increasing light intensity (r2 = 0.95, P < 0.01). It was concluded that at 20 degrees C, increasing light intensity favors less chla synthesis and higher geosmin synthesis; at 17 microE/m2/s, increasing temperature stimulates chla production (to 25 degrees C) while repressing geosmin synthesis (above 20 degrees C). Nutritional factors promoting biomass, chla, and geosmin synthesis by Anabaena sp. were also investigated. For cultures grown at 17 microE/m2/s and 20 degrees C for 20 days, both ammonium-N and nitrate-N generally enhanced the growth of Anabaena sp. Nitrate-N promoted more chla production (r2 = 0.99) than ammonium-N. Geosmin synthesis was directly correlated with ammonium-N concentrations (r2 = 0.89), with low nitrate-N (123.5 micrograms/l) favoring maximal geosmin production (2.8 micrograms/l). Increasing nitrate-N concentrations promoted a three-fold increase in chla content with geosmin synthesis decreased by two-fold. Geosmin/mg biomass was directly related to ammonium-N concentration; high nitrate-N levels suppressed geosmin production. No geosmin was detected at or below 118 micrograms phosphate-phosphorus/l. Geosmin, dry weight biomass, and chla production were correlated with increasing phosphorus (P) concentration (r2 = 0.76, 0.96 and 0.98, respectively). No geosmin was detected when copper was present in growth media at or above 6.92 micrograms Cu2+/l (CuSO4.5H2O). Dry weight biomass and chla production were negatively correlated with Cu2+ ion concentrations.     

Softening hard wellwaters with Moringa oleifera seed extracts

A study into the use of Moringa oleifera seed extract in the softening of hard water has been carried out with samples from 17 hand‐dug wells in Kano metropolis, Nigeria. Of the 17 samples tested, 7 contained calcium and magnesium hardness while 10 contained calcium hardness only. The softening dose of Moringa oleifera varied from 700–2000 mg/l and the required dose increased with initial hardness of the samples. The level of softening was found to be directly proportional to the dose used; and water samples with both calcium and magnesium hardness required more Moringa oleifera than samples with only calcium hardness, to achieve the same level of softening. All samples had hardness reduced to ≤ 200 mg/l CaCO₃, the highest desirable concentration of hardness in drinking water recommended by the WHO. The softening mechanism was postulated to be a combination of adsorption and precipitation of the soluble hardness causing ions to insoluble solids/flocs. The adsorption isotherm developed was linear and of the Langmuir type.     

Effect of domestic effluents on groundwater quality: A case study

In order to evaluate the effects of seeping septic effluents on the quality of groundwater in a watershed, a number of contaminants such as nitrate, phosphorus, chloride, lead, copper, iron, and manganese, were studied. To determine the extent of contamination, a network of observation wells was established in the drainage area of the septic systems. Groundwater samples from the observation wells were collected in the spring, summer and fall of 1981, 1982 and 1983. The samples were extracted for the determination of various contaminants by standard methods.The results indicated that nitrate, phosphorus, and chloride were coming from septic systems and were moving into groundwater. Nitrate and chloride levels were less than the maximum allowable limits in drinking water, whereas phosphorus was above the limits in 41% of the wells. According to the data obtained, the concentrations of iron and manganese were above the recommended levels in 27 and 50% of the wells, respectively. The concentrations of lead and copper were below the allowable maximum levels in drinking water. The results indicate contamination of groundwater in the study area with phosphorus, which could be attributed to domestic use of detergents, and iron and manganese, which could be attributed to corrosion of household pipes.     

Water Quality Changes in a Septic Tank Effluent Discharged to the Chalk

B ucket-type samplers were installed in the unsaturated zone to intercept septic tank effluent descending through the Chalf at Snowdown, Kent. Better than 90 per cent removal of BOD and COD, and of the order of 99 per cent removal of coiform bacteria, were observed after downward percolation through 2.1 m of Chalk. Nitrification of ammonia had begun at that depth, but not at intermediate depth. The results, though limited, suggest that septic tank effluent is purified in the Chalk in a similar way to settled sewage.     

Contamination of headwater streams in the United Kingdom by oestrogenic hormones from livestock farms

Most studies of hormonal activity in rivers have focused on inputs from sewage treatment works (STW), and their consequences for endocrine disruption in fish. It is possible that livestock is contributing to this hormonal activity in rivers. This study represents a search for evidence of steroid hormone contamination in streams associated with livestock farms. The majority of the 10 sites selected were streams running through dairy farms, although some examples of beef, sheep and pigs were included. Passive water samplers (Polar Organic Chemical Integrative Samplers-POCIS) were deployed up- (control) and down-stream of the farms for 3 to 10 weeks (mean=39 days) during the period November 2004 to January 2005. At one site, water samples were also taken automatically during rainfall events. All samples were solvent-extracted. Total oestrogenic activity in concentrates of the extracts was analysed using the Yeast Estrogen Screen (YES) calibrated against 17beta-oestradiol (E2), while oestrone (E1), E2 and 17alpha-ethinylestradiol (EE2) were analysed by liquid chromatography-mass spectrometry (LC-MS/MS). Stream water from the entirety of only one rainfall event was sampled directly, but this revealed background activity (E2 equivalents) of 0-0.3 ng/l, rising to a transient peak of 9.4 ng/l. Average oestrogenic activity at this site as estimated from the POCIS samplers was 1.8-2.7 ng E2 equiv./l. Estimated average oestrogenic activity across all sites (with one exception) lay in the range 0-26.5 ng E2 equiv./l (mean=2.0 ng/l; S.D.=5.1), based on the POCIS samples. The outlier was 292 ng/l, and this could not be specifically linked with livestock rearing. 92% of monitoring stations (at least one on each farm) contained some oestrogenic activity, and activity was higher at downstream sites in 50% of cases. Although no EE2 was detected analytically in any stream, E1 and E2 were almost ubiquitous, with E2 equivalents ranging from 0.04 to 3.6 ng/l across all sites. Furthermore, steroid concentrations downstream of livestock were higher than upstream in 60% of cases, more markedly so than for the YES data. In several cases, activity upstream was greater than downstream, and this tended to be associated with higher activity than could be accounted for by the hormone analyses. Both the YES and chemical analytical data suggest that fish in headwater streams on or near some livestock farms may be at risk of endocrine disruption.     

Mercury levels in Oryza sativa cultivated in Philippine small-scale mining villages

Soil physico-chemical parameters and total mercury concentrations were measured in soil and rice plant samples collected over a cropping period grown in areas near mine tailings ponds in two Philippine small-scale mining (SSM) communities. Step-wise regression analysis relating environmental parameters to Hg uptake showed that pH has a highly significant effect on Hg content in the samples (p < 0.001) while temperature, contrary to previous studies, had no significant effect. The mean total Hg concentrations appeared to be significantly lower in rice plant parts sampled in control sites than in the contaminated sites in both SSM communities: 0.020 and 2.832 mg/kg, respectively in Aroroy, Masbate and 0.004 and 0.016 mg/kg, respectively in Fidelisan, Sagada. Harvested rice grains from the Masbate sampling sites further revealed total Hg concentration at 0.1331 mg/kg, exceeding the maximum permissible limit of 0.02 mg/kg Hg contamination. The study shows that Hg use in SSM activities and the cumulative effects of prolonged exposure to the metal through regular consumption of the village-cultivated rice may put the local residents at risk of health problems related to mercury.     

Occurrence of Cryptosporidium in agricultural surface waters during an annual farming cycle in lowland UK

A 17-month survey based on weekly testing for Cryptosporidium oocysts in surface waters draining a livestock farm on a Warwickshire (UK) estate has shown that the parasite is present throughout the year, with the highest frequency of occurrence and maximum concentrations during the autumn and winter. The 190 ha farm is managed as an exemplar for a teaching institution. There were up to 800 livestock present at peak times of year in the catchment of the stream draining the estate. Oocysts were concentrated from grab samples by a flocculation procedure, stained with monoclonal antibody and detected by fluorescence microscopy. Overall, 274/418 (66%) of samples were positive for Cryptosporidium. Where the stream passed from the estate, the occurrence was 79%, with mean and median oocysts/l of 0.48 and 0.2, respectively. Highest oocyst levels coincided with calving and increased wild animal numbers following breeding. There was no correlation of oocyst levels with rainfall or slurry spreading. Cryptosporidium was also frequently found in a pond on arable land (no livestock) indicating that wild animals alone contributed oocysts to surface waters. These results from a well managed livestock farm may represent a typical natural baseline for levels of occurrence and concentration of Cryptosporidium oocysts in surface waters of the lowland agricultural environment of the UK.     

生物铁法处理维生素B1生产废水

生物铁法是一种新型的强化活性污泥工艺,处理高浓度、难生物降解维生素B1生产废水具有很大的优势.当进水COD维持在8 000 mg/L时,对COD的去除率可达94%以上,比普通活性污泥法高9.7%;当进水NH3-N维持在420 mg/L时,对NH3-N的去除率为59.7%,比普通活性污泥法高18.4%;部分颗粒化的生物铁污泥沉降效果好,能保证系统有较高浓度的回流污泥,从而提高了曝气池的污泥浓度.     

复合式竹丝填料生物反应器处理化粪池出水

为寻找适合化粪池出水的处理工艺,采用批式试验研究了复合式竹丝填料生物反应器对化粪池出水中COD、SS的去除效果。结果表明:复合式竹丝填料生物反应器能有效去除化粪池出水中的COD和SS,平均去除率分别达到了85.4%和90%以上;复合式竹丝填料生物反应器的微生物数量较多、微生物链较长、微生物种群丰富;复合式竹丝填料生物反应器中的污泥增加量极少。将复合式竹丝填料生物反应器内的活性污泥和竹丝分开组成两个独立的生物反应器并处理化粪池污水,结果发现,竹丝生物膜反应器能在短期(18h)内超过活性污泥反应器的处理效果,且竹丝生物膜反应器的产泥量很低。可见,竹丝填料较为适合处理化粪池出水,是一种价格低廉、污染少、运行管理费用较低的良好填料。     

Occurrence and concentrations of pharmaceutical compounds in groundwater used for public drinking-water supply in California

Pharmaceutical compounds were detected at low concentrations in 2.3% of 1231 samples of groundwater (median depth to top of screened interval in wells = 61 m) used for public drinking-water supply in California. Samples were collected statewide for the California State Water Resources Control Board's Groundwater Ambient Monitoring and Assessment (GAMA) Program. Of 14 pharmaceutical compounds analyzed, 7 were detected at concentrations greater than or equal to method detection limits: acetaminophen (used as an analgesic, detection frequency 0.32%, maximum concentration 1.89 μg/L), caffeine (stimulant, 0.24%, 0.29 μg/L), carbamazepine (mood stabilizer, 1.5%, 0.42 μg/L), codeine (opioid analgesic, 0.16%, 0.214 μg/L), p-xanthine (caffeine metabolite, 0.08%, 0.12 μg/L), sulfamethoxazole (antibiotic, 0.41%, 0.17 μg/L), and trimethoprim (antibiotic, 0.08%, 0.018 μg/L). Detection frequencies of pesticides (33%), volatile organic compounds not including trihalomethanes (23%), and trihalomethanes (28%) in the same 1231 samples were significantly higher. Median detected concentration of pharmaceutical compounds was similar to those of volatile organic compounds, and higher than that of pesticides.Pharmaceutical compounds were detected in 3.3% of the 855 samples containing modern groundwater (tritium activity > 0.2 TU). Pharmaceutical detections were significantly positively correlated with detections of urban-use herbicides and insecticides, detections of volatile organic compounds, and percentage of urban land use around wells. Groundwater from the Los Angeles metropolitan area had higher detection frequencies of pharmaceuticals and other anthropogenic compounds than groundwater from other areas of the state with similar proportions of urban land use. The higher detection frequencies may reflect that groundwater flow systems in Los Angeles area basins are dominated by engineered recharge and intensive groundwater pumping.     

Quantitative assessment of estrogenic activity in the water environment of Korea by the E-SCREEN assay

In this study, the E-SCREEN assay was optimized and validated for the sensitive quantitative determination of the total estrogenicity in river samples. River water and sediment samples were collected and analyzed with the E-SCREEN. River water (10 l) was extracted using combined solid-phase extraction in static adsorption mode with Soxhlet extraction. Estrogenic pollutants adsorbed to the XAD-4 resin were recovered with 98.24 +/- 5.90% efficiency by elution with ethyl acetate and dichloromethane (1:9). The detection limit by 17beta-estradiol equivalent concentration (EEQ) of the E-SCREEN assay was 8.03 pg EEQ/l. Among the water samples, the estrogenic activity was observed to be higher downstream of the Kumho river (7.43 ng EEQ/l) and upstream of Kum river (2.05 ng EEQ/l) than in other samples. More than 3 mg of equivalent sediment samples from the Kumho river, Kum river and Miho stream showed partial agonistic effects, and the Mankyung river showed a partial agonistic effect with only 1.5 mg of sediment. The highest value of RPE was 83.34 downstream of the Kumho river, and the lowest value of RPE was 6.52 downstream of the Miho stream. Full estrogen agonistic activities were observed downstream of the Kumho river and upstream of the Kum river. The partial agonistic activity was observed in upstream of the Kumho river, downstream of the Mankyung river, and upstream of the Miho stream, and no agonistic action was observed downstream of the Kum river or Miho stream, or upstream of the Mankyung river. The total estrogenic activity in the river water and sediment samples was between 0.50 pg/L and 7.4 ng/L, 3.39 pg/g and 10.70 pg/g.     

谈化粪池的应用与发展

简述了化粪池的使用现状,分析了化粪池使用中存在的问题,介绍了化粪池的布置和设计,展望了化粪池的发展趋势,指出化粪池的设置应与城市污水处理统筹考虑。     

Pollution in the water supply wells of Khartoum, Sudan

 The supply of water to Khartoum, Sudan, is from wells tapping aquifers in the Nubian Sandstone Formation. The boreholes are located in residential areas where sewage disposal is by means of a siphon septic tank system draining into the water table in the upper alluvial deposits. The aquifers are leaky to unconfined in nature and as the lower groundwater moves from the Nile towards the residential areas, it is susceptible to pollution from the septic tanks. Evidence that such pollution is occurring was found in three production wells where the presence of E. coli bacteria was identified. Received: 9 July 1998 · Accepted: 20 May 1999     

Lead contamination in tap water of households with children in Lower Saxony, Germany

Lead has numerous acute and chronic adverse effects on human beings. This is especially true for infants and children. The main path of lead ingestion in children can be different according to housing and living situation. The intake of lead through drinking water is commonly due to metal corrosion. The users plumbing can be an important factor. In recent years, many lead pipes in Germany have been replaced by pipes made of an alternative material. The aim of this study is to assess the present state of drinking water contamination and the resulting exposure of infants to lead. For this purpose mothers of new-born babies were offered a free examination of their drinking water. After a written declaration of consent had been obtained and after the infant in question had reached an age of 3 months, a stagnation sample of cold tap-water after overnight stagnation together with a random daytime sample was obtained from the family. The collected samples were analysed by atomic absorption spectrometry for their lead concentration. In total, 1485 samples from households were collected. Of the 1434 stagnation samples, 3.1% had lead concentrations greater than 0.01 mg/l (recommended limit of the WHO) and 0.6% had concentrations above the limit of the German drinking water regulation (0.04 mg/l). The values for the 1474 random daytime samples were 2.1% above 0.01 mg/l and 0.2% greater than 0.04 mg/l, respectively. By region, the areas Bovenden, Friedland, Duderstadt, Northeim and Rosdorf were particularly affected. The highest measured concentrations of lead in the stagnation samples were 0.11 mg/l and 0.15 mg/l in the random daytime samples, respectively.     

The influence of the abandoned Kalecik Hg mine on water and stream sediments (Karaburun,Izmir, Turkey)

This study covers the geochemical investigations on water and stream sediments to evaluate the influence from the abandoned Kalecik Hg mine. The groundwater samples (S5, S8, S9, WW10) are neutral, slightly alkaline waters which have pH values varying between 7.3 and 7.5. Electrical conductivity (EC) values of groundwaters for spring samples are low (250-300 microS/cm). However, groundwater obtained from a deep well has a higher EC value of 950 microS/cm. Hg concentrations of groundwater samples vary between 0.01 and 0.13 microg/l. Hg concentrations of other water samples taken from mining area from surface waters and adits are between 0.10 and 0.99 microg/l. Adit water (A4) collected at the mine has the highest Hg content of 0.99 microg/l and a pH of 4.4. Trace element concentrations of mine water samples show variable values. As is observed only in MW1 (310 microg/l). A4 was enriched in Cd, Co and Cr and exceed the Turkish drinking water standards (Türk Standartlari Enstitüsü, 1997). Cu concentrations vary between 6.0 and 150 microg/l and are below the Turkish water standards. Mn concentrations in mine waters are between 0.02 and 4.9 mg/l. Only for sample A4 Mn value (4.9 mg/l) exceeds the standard level. Ni was enriched for all of the mine water samples and exceeds the safe standard level (20 microg/l) for drinking water. Of the major ions SO(4) shows a notable increase in this group reaching 650 mg/l that exceeds the drinking water standards. Stream sediment samples have abnormally high values for especially Hg and As, Sb, Ni, Cr metals. With the exception of sample Ss6 of which Hg concentration is 92 mg/kg, all the other samples have Hg contents of higher than 100 mg/kg. Pollution index values are significantly high and vary between 69 and 82 for stream sediment samples.