The use of Stigeoclonium subsecundum (cholorophyceae) as a bioassay organism—III. Response to intermittent chlorination

The toxicity of intermittent chlorination to an attached, filamentous, green alga (Stigeoclonium subsecundum) was found to be related to the biomass of the alga at the beginning of the bioassay. Minimal resistant biomass (MRB) was a term used to describe the lowest biomass of algae able to survive and continue to grow when subjected to a specific level of chlorine at intervals of 6 h for a period of one week. This ability to survive was due to changes in the morphology of the algal filaments and the algal mat.     

Fecal coliform accumulation within a river subject to seasonally-disinfected wastewater discharges

As pathogen contamination is a leading cause of surface water impairment, there has been increasing interest in the implications of seasonal disinfection practices of wastewater effluents for meeting water quality goals. For receiving waters designated for recreational use, disinfection during the winter months is often considered unnecessary due to reduced recreational usage, and assumptions that lower temperatures may reduce pathogen accumulation. For a river subject to seasonal disinfection, we sought to evaluate whether fecal coliforms accumulate during the winter to concentrations that would impair river water quality. Samples were collected from municipal wastewater outfalls along the river, as well as upstream and downstream of each outfall during the winter, when disinfection is not practiced, and during the summer, when disinfection is practiced. During both seasons, fecal coliform concentrations reached 2000–5000 CFU/100 mL, nearly an order of magnitude higher than levels targeted for the river to achieve primary contact recreational uses. During the summer, wastewater effluents were not significant contributors to fecal coliform loadings to the river. During the winter, fecal coliform accumulated along the river predominantly due to loadings from successive wastewater outfalls. In addition to the exceedance of fecal coliform criteria within the river, the accumulation of wastewater-derived fecal coliform along the river during the winter season suggests that wastewater outfalls may contribute elevated loads of pathogens to the commercial shellfish operations occurring at the mouth of the river. Reductions in fecal coliform concentrations between wastewater outfalls were attributed to dilution or overall removal. Combining discharge measurements from gauging stations, tributaries and wastewater outfalls to estimate seepage, dilution between wastewater outfalls was estimated, along with the percentage of the river deriving from wastewater outfalls. After accounting for dilution, the residual reductions in fecal coliform concentrations observed between outfalls were attributed to actual fecal coliform removal. The estimated rate of removal of 1.52 d^?1 was significantly higher than die-off rates determined by previous researchers at similarly low temperatures in laboratory batch experiments, indicating the potential importance of other removal mechanisms, such as predation or sedimentation.     

The occurrence and role of Bdellovibrio bacteriovorus in a polluted river

Bdellovibrio bacteriovorus was found to occur in a polluted river in numbers averaging, over an 18 month period, 10–100 parasites/ml. The parasite was not able to grow at river temperatures on host concentrations below about 10⁶–10⁷ bacteria per ml and even at these had a doubling time of only 24–48 h. The results have indicated that the parasite was not important in reducing the bacterial population of the river studied.     

The growth of cladophora glomerata in a river receiving sewage effluent

A considerable improvement in the natural flora of the River Great Stour has occurred since the mid-1960s when dense growths of Cladophora glomerata dominated sections of the river with the disappearance of some rooted macrophytes. Cladophora growths in the river in response to changing river conditions and sewage treatment operations during a thirty year period are reviewed. A vegetation mapping programme undertaken from 1978 to 1982 to assess the influence of a sewage treatment works discharge on the growth of the filamentous alga has shown that previous recommendations to reduce dissolved phosphorus concentrations in the final effluent need not be implemented.     

Life history responses of Daphnia magna feeding on toxic Microcystis aeruginosa alone and mixed with a mixotrophic Poterioochromonas species

The toxic effects of a mixotrophic golden alga (Poterioochromonas sp. strain ZX1) and a cyanobacterium Microcystis aeruginosa grazed by Poterioochromonas to a cladoceran were investigated through life history experiments using Daphnia magna. Poterioochromonas cultured in two ways (fed M. aeruginosa in an inorganic medium or grown in an organic medium) both induced starvation-like effects on D. magna, indicating that Poterioochromonas is neither acutely toxic nor a good food for D. magna. Despite a microcystin-LR content of 10⁻⁸ μg cell⁻¹ in M. aeruginosa, no toxins were accumulated in Poterioochromonas fed the cyanobacterium. The toxic effect of M. aeruginosa to D. magna was significantly reduced in the presence of Poterioochromonas, which may be performed in two ways: decrease M. aeruginosa cells ingestion of D. magna by grazing on M. aeruginosa; and decrease the toxicity of the medium by degrading the toxins released by M. aeruginosa. This study provides new information on the interactions between a cyanobacterium and its grazer under laboratory conditions and may increase our understanding of the ecological significance of such interactions in the aquatic food webs.     

The effect of sewage and industrial waste discharges on the primary production of a shallow turbulent river

Sewage and industrial waste discharges have been found to have a deleterious effect on the primary productivity of the shallow turbulent tropical river Khan (Indore) India. Even though net primary production rates have exceeded the respiration rates in the early recovery zone, the industrial wastes and sewage discharges have been found to decrease the overall productivity of the river. The above studies have been compared with other investigations in the temperate regions of the world, which generally refer to the effects of organic pollution on the primary productivity of the running waters. The present investigations lead to a generalized observation that in tropical running waters, toxic industrial wastes and sewage discharges have a depressing effect on the overall production rates. However, comparable studies in the temperate regions are nonexistent, as the studies in the temperate regions mainly refer to organic pollution and do not take into account the effects of toxic industrial waste and sewage discharges.     

The use of Bacillus thuringiensis var. israelensis to control the nuisance fly Sylvicola fenestralis (Anisopodidae) in sewage filter beds

The effectiveness of using the microbial insecticide Bacillus thuringiensis var. israelensis (Bti) to control the nuisance fly Sylvicola fenestralis at Rossendale Sewage Works, Lancashire, was investigated. Following a provisional trial in 1987, the whole Works (28 filter beds) was treated with a two-stage application of Bti in 1988; the first application in late April was separated from the second in late May by about half the length of the Sylvicola life-cycle. The Bti treatment was timed to reduce fly nuisance in June, the month when most complaints (71%) had been received. For each application, 0.161. of the Bti preparation, containing nearly 10¹⁰ spores·cm⁻³, was applied per square metre of bed surface. An 80 and 98% kill of Sylvicola larvae was recorded following the first and second applications respectively. The lower kill achieved by the first application was believed to be due to insufficient mixing of the Bti with the settled sewage prior to dosing. Nuisance caused by the flies was considerably reduced; there were no complaints from the public during June, although a few were received in late July, early August. Sewage purification efficiency was not affected by Bti treatment. The maximum concentration of Bti spores in the Works' effluent was 7 × 10⁴ spores·cm⁻³. This concentration did not appear to affect the already impoverished macro-invertebrate fauna of the receiving river.     

Some physiological responses of rainbow trout (Salmo gairdneri) to intermittent monochloramine exposure

Rainbow trout (Salmo gairdneri) were exposed for 2.5 h to monochloramine (NH₂Cl) at an average concentration of 0.16 or 0.23 mg l⁻¹ (and with peak concentrations of 0.4 or 0.6 mg l⁻¹) three times daily. This simulates conditions in the outfall area of many electric power plants. Heart rate, opercular movement, cough frequency, arterial PO₂, lactate, hemoglobin and methemoglobin were monitored. The trout responded to chloramine pulses with slight increases in opercular movement, bradycardia, and a large increase in cough rate. These factors approached control rates between periods of exposure to a peak concentration of 0.4 mg l⁻¹, but not when the peak was 0.6 mg l⁻¹. Neither hemoglobin or lactate changed, while arterial PO₂ decreased slightly but not significantly. Methemoglobin concentration increased markedly at the end of each period of exposure with some recovery between them. In contrast to free chlorine, which causes acute hypoxemia due to gill damage, chloramine at these concentrations causes little if any hypoxemia. The elevated methemoglobin levels, not seen following exposure to free chlorine, indicate that perhaps chloramine is entering the blood stream to an extent that does not occur with free chlorine. Methemoglobinemia is probably not the proximate cause of death.     

Transport and fate of Cryptosporidium parvum oocysts in intermittent sand filters

The transport potential of Cryptosporidium parvum (C. parvum) through intermittent, unsaturated, sand filters used for water and wastewater treatment was investigated using a duplicated, 2³ factorial design experiment performed in bench-scale, sand columns. Sixteen columns (dia=15 cm, L=60 cm) were dosed eight times daily for up to 61 days with 65,000 C. parvum oocysts per liter at 15°C. The effects of water quality, media grain size, and hydraulic loading rates were examined. Effluent samples were tested for pH, turbidity, and oocyst content. C. parvum effluent concentrations were determined by staining oocysts on polycarbonate filters and enumerating using epifluorescent microscopy. At completion, the columns were dismantled and sand samples were taken at discrete depths within the columns. These samples were washed in a surfactant solution and the oocysts were enumerated using immunomagnetic separation techniques.The fine-grained sand columns (d₅₀=0.31 mm) effectively removed oocysts under the variety of conditions examined with low concentrations of oocysts infrequently detected in the effluent. Coarse-grained media columns (d₅₀=1.40 mm) yielded larger numbers of oocysts which were commonly observed in the effluent regardless of operating conditions. Factorial design analysis indicated that grain size was the variable which most affected the oocyst effluent concentrations in these intermittent filters. Loading rate had a significant effect when coarse-grained media was used and lesser effect with fine-grained media while the effect of feed composition was inconclusive. No correlations between turbidity, pH, and effluent oocyst concentrations were found. Pore-size calculations indicated that adequate space for oocyst transport existed in the filters. It was therefore concluded that processes other than physical straining mechanisms are mainly responsible for the removal of C. parvum oocysts from aqueous fluids in intermittent sand filters used under the conditions studied in this research.     

The use of Stigeoclonium subsecundum (chlorophyceae) as a bioassay organism II. The use of stigeometers in a continuous flow system

A technique was developed for the use of Stigeoclonium subsecundum Kutz., an attached, filamentous, green alga, as a bioassay organism. The procedure involved the settling of a freshly blended suspension of algal cells onto the surface of glass slides. The production, release, and attachment of zoospores as well as the production of rhizoids from the blended filaments produced an attached algal mat on a glass surface. The pigment extract absorbance and the dry weight of the algae attached to each glass slide were normally distributed about a mean.     

The selection and limitations of phenol as a reference toxicant to detect differences in sensitivity among groups of rainbow trout (Salmo gairdneri)

Phenol was better than sodium azide, sodium pentachlorophenate, copper sulphate and dodecylsodium sulphate in detecting differences in sensitivity among groups of rainbow trout (Salmo gairdneri). Phenol detected differences in sensitivity among strains of trout and could discern the effects of starvation, temperature stress and pre-exposure to 0.04 mg l⁻¹ chlorine on the sensitivity of trout to phenol, but not the effects of three brands of food and high mortality during holding. The sensitivity of rainbow trout to phenol was independent of weight and loading density in the bioassays. The use of phenol as a reference toxicant for the rapid detection of differences in sensitivity among groups of fish is limited because differences can only be detected by comparing the sensitivity of an unknown group of fish to that of a known, unstressed group of fish in the same bioassay. The concept of a single reference toxicant appropriate for bioassays with a variety of chemicals is questionable because differences among groups of fish, which are detectable by a reference toxicant, may not affect the results of bioassays with other chemicals. A series of physiological and behavioural screening tests and diagnostic health checks may be more useful than reference toxicants to identify groups of fish which should not be used in bioassays.     

河道淤泥制砖技术优化及效益评价

介绍了河道淤泥制砖实施过程中工艺优化方案,包括淤泥除杂工艺、河道淤泥干燥工艺、粉煤灰掺配、产品质量控制,并对河道淤泥砖的经济效益、社会效益以及生态效益进行评价。江苏海安利用河道淤泥制砖多年的实践表明,河道淤泥制砖属于新型墙材,技术可行,综合效益好。     

The use of whittaker's components of diversity in summarising river survey data

The use of β diversity, which is a measure of taxonomic change, allows information to be presented as to the extent of faunal change along a river section. The γ diversity is the normal Shannon diversity for an aggregated pair of stations. Since the β and γ diversity measures are, in practice, independent, they measure different aspects of the community composition namely structural and taxonomic changes. Graphical presentation of the β and γ diversities gives a better grouping of similar sites and separation of dissimilar sites than is achieved by using the Shannon function for each separate site, thus enabling points of change to be readily detected. Due to its reliance upon both community structure and taxonomic turnover rather than indicator species it can be used in situations where the natural unpolluted fauna is unknown. Since the method is a simple extension of the Shannon index, already widely used by many biologists, it could be calculated without difficulty.     

Developing indicators to detect changes in the seasonality,frequency and duration of medium and high river flows

Indicators specifically designed to detect changes in the seasonality, frequency and duration of medium and high river flows have been developed to monitor river flow regimes. Four primary methods to display and interpret the indicator results have been developed to meet the needs of different target audiences. The variability in annual indicator values is accommodated by comparing the probability distributions of the annual values rather than seeking to identify trends in annual values themselves. Changes in the distribution of indicator values are consistent with those anticipated to arise as a result of climate change. This finding is confirmed by calculating the indicators from example flow data for catchments across England and Wales, which has been perturbed to reflect climate change scenario model outputs.     

Histopathological effects of intermittent chlorine exposure on bluegill (Lepomis macrochirus) and rainbow trout (Salmo gairdneri)

Fish were exposed to multiple pulses of free residual chlorine in the water at four concentrations ranging from sublethal to lethal levels. Histological examinations were made of moribund fish and those surviving the exposures.Sublethal concentrations caused moderate gill hyperplasia and swelling of the lamellar epithelial cells. Lethal concentrations caused extensive hyperplastic lesions of gill epithelium. No kidney damage was seen in any of the fish. Liver glycogen was severely depleted, probably as a result of the hypoxemia produced by the gill damage. Hepatic necrosis was seen in fish exposed to high chlorine concentrations and these lesions were more extensive at elevated temperatures. From these observations and other physiological studies, it is concluded that death in fish from exposure to several pulses of free residual chlorine is due primarily to histological damage to the gills causing blockage of respiratory gas transport across the gill epithelium.     

Morphological changes in the gill of carp (Cyprinus carpio L.) exposed to acutely toxic concentrations of methyl bromide

The acute toxicity of methyl bromide (CH₃Br) to carp (Cyprinus carpio L.) was determined in experiments with a 4 h exposure period. The 4 h-LC₅₀ was calculated at approx. 17 mg 1⁻¹, i.e. the order of magnitude of actually encountered peak concentrations in surface water. The concentration-effect curve was found to be very steep and the response was somewhat delayed. Morphological damage to the gill epithelium, indicative of alkylation of cell membranes, was the most pronounced effect of CH₃Br. It consisted of initial swelling of the lymphatic space and vacuolization of the epithelial cells, followed by disintegration of the epithelium and invasion of leucocytes. Death of the fish was probably caused by suffocation.     

回弹法检测混凝土强度的探究

从混凝土本构关系及强度与硬度的关系两方面,探讨了回弹法检测混凝土强度中,回弹值—碳化深度—强度这种推断方法的不准确性,并指出如果回弹法测量结果离散性较大时,应选择其他更合适的方法进行混凝土强度测试。     

The use of uric acid as a method of tracing domestic sewage discharges in riverine, estuarine and coastal water environments

The chemical tracking of sewage effluents discharged into fresh and saline waters presents difficulties, especially in estuaries. The main difficulty is caused by the dissolved constituents being used to monitor the effluent also occurring naturally at similar levels. Uric acid is present at significant levels in untreated sewage and is not normally found in unpolluted waters. Until now no suitable routine method has been available for uric acid estimation in fresh and saline waters at levels normally encountered in the environment. In this paper we describe a recently developed technique using high-performance liquid chromatography which estimates uric acid in both fresh and saline waters in the range 1–10,000 μg l⁻¹ with a precision (2σ) of ±20% at 2 μg l⁻¹, ±4% at 40 μg l⁻¹ and ±2% at 10 mg l⁻¹.     

间歇式沥青拌和站使用经验谈

本文对间歇式沥青拌和站在使用吵应该注意的问题作了阐述,并对经常出现的故障进行分析。