A simple, inexpensive in situ method for assessing acute toxicity of effluents to fish

Test chambers for conducting in situ fish bioassays were constructed from 81. polyethylene bottles. Yearling fathead minnows (Pimephales promelas) and young-of-the-year bluegill (Lepomis macrochirus) demonstrated greater than 50% survival in the chambers after 65 days of exposure in a reservoir, river and creek. Fathead minnow survival was substantially greater than that of bluegils. The chambers provide a simple, inexpensive, sensitive technique to screen effluents for toxicity.     

A simple cultivation unit for the evaluation of algal growth potential and toxicity of water

The design presented here enables a makeshift cultivation unit to be assembled for AGP evaluation after Lukavský (Lukavský J. Water Res. 17, 549–558, 1983) i.e. using solid media in a microtitration plate. The unit consists of common laboratory components and is very cheap and reliable.     

A new and simple method for recuperation of enteroviruses from water

A new and simple method for recuperation of enteroviruses from water is described here. The sample to be analyzed, with a volume arbitrarily fixed to 101, is adjusted to pH = 3.5 with hydrochloric acid. It is then injected under low pressure (0.15 bar) by the lower end of a column containing glass powder (50 g). The calibration of the water's upward speed enables the glass powder to remain in dynamic suspension. Under these conditions, poliovirus is quantitatively adsorbed on the glass powder. The virus is then eluted from the glass powder with 50 ml of a glycine buffer (pH = 11.5) and thus concentrated 200 times in the final eluate. The total duration of operation does not exceed 2 h 30 mn. The recuperation efficiency is about 40–60% and does not depend on initial virus concentration in sample, and this, for virus concentrations ranging from 1 to 10⁴PFU/1.     

A better water quality indexing system for rivers and streams

The development of a better system for indexing water quality and its application to four water use classes are described. There are three dominant use classes: bathing, water supply, and fish spawning, and one general use class. In all of them protection of aquatic life is included. To ensure that the index score tells us something useful and does not hide important information as current indexes (or indices) tend to do, the water quality variable giving the lowest score (i.e. the minimum operator) has been employed to produce the final index score. Preliminary indications are that this is a more useful aggregation method than the more commonly used additive, and multiplicative techniques. Index development has been linked to recommended water quality standards developed for New Zealand water legislation. The indexes are intended to assist in the dissemination of water quality information, particularly to lay-people.     

A simple technology for arsenic removal from drinking water using hydrotalcite

The use of a synthetically prepared clay material, hydrotalcite (HT), for the removal of arsenite (As(III)) and arsenate (As(V)) from drinking water is described. Percolation through HT of water containing 500-1000 microg/L As (levels often found in As-contaminated well water) produced leachate with As levels well below 10 microg/L. The technology could be coupled to that used in less-developed regions for removing organisms from drinking water, viz. leaching through porous pots and filter candles. The 'spent' HT is easily converted into valuable phosphatic fertilizer that would have an insignificant effect on soil arsenic levels, thereby reducing the overall cost of manufacture and distribution.     

A simple method for evaluating liquefaction potential from shear wave velocity

The simplified procedure using shear wave velocity measurements is increasingly used to evaluate the seismic liquefaction potential of soils. This procedure is based on finding the boundary separating the liquefaction and non-liquefaction cases through the analysis of liquefaction case histories, following the general format of the Seed-Idriss simplified procedure based on standard penetration test (SPT) data. It is noted that many assumptions have been made in the simplified procedure. This paper develops a simple method for evaluating the liquefaction potential of soils from shear wave velocity by using the optimum seeking method to directly analyze the liquefaction history data and quantify the influence of major factors affecting the liquefactions potential of soils. The factors considered are the earthquake magnitude, the vertical effective overburden stress, the shear wave velocity, the peak acceleration at the ground surface of the site, and the fines content of the soil. The most important factor has been identified as the shear wave velocity. The developed method uses the measured data directly and in a very simple way. Neither stress-correction of shear wave velocity nor calculation of cyclic shear stress as in the simplified procedure is required. Comparisons indicate that the developed simple method has a higher success rate for evaluating liquefaction potential of soils than the simplified procedure. A case study is presented to illustrate the application of the developed simple method and further confirms its accuracy.     

A simple conduction model for skin burns resulting from exposure to chemical fireballs

A simple conduction model is developed for skin burns resulting from a short-duration heat pulse of the type that commonly occurs with typical chemical fireballs. This model predicts the absorbed heat values necessary to produce second and third degree burns for constant heat pulses of 1 to 36 s duration. The results of the model are shown to correlate well with test data for swine and human skin.     

A simple rainfall intensity formula for Singapore

A simple rainfall intensity formula (RIF) for Singapore is proposed. Basically, it is derived from the Intensity–Duration–Frequency (IDF) curves. By applying the least squares method, the parameters of the RIF are optimised. It is convenient to apply the improved formula for programming and practical applications, compared with the conventional method of checking the IDF curves. The results furnished by the proposed formula are in very good agreement with those obtained from the IDF curves.     

A model for identifying the vulnerability of streams and rivers to land use-induced changes

This article describes a model for identifying the vulnerability of streams and rivers to land-induced change. Landscape architects are frequently asked to make land use recommendations which affect landscape change. The challenge is to organize information to aid landscape architects in making responsible recommendations. This model considers three types of spatial information: (1) sources of land use-induced change; (2) intensity of drainage within watersheds; and (3) sensitivity of drainage basins to change. The model also demonstrates the use of a Geographic Information System (GIS) and its application. The strength of this model is that it provides landscape architects with both time- and cost-efficient means of assessing the vulnerability of streams and rivers with existing data. It further directs site-specific investigation to areas which are identified and prioritized with regard to the relative vulnerability of streams and rivers to land-induced change.     

A simple model for the derivation of illuminance values from global solar radiation data

This paper presents a new simple luminous efficacy model for global horizontal irradiance. The objective is to derive values of outdoor global horizontal illuminance data from typical local weather station data including global horizontal irradiance and Humidity Ratio of outdoor air. The proposed luminous efficacy model incorporates, as the main influencing variable, the Clearness Factor, which is an original derivative from the Clearness Index. Two further variables are included in the model formulation. These are the Humidity Ratio and the solar altitude. Moreover, the model includes a location-dependent variable, which may be derived from the latitude information. The paper includes the result of the statistical analysis of the relationship between the model predictions and the measured data. The results of this analysis display a good agreement between predictions and measurements.     

Endogenous centers: A simple departure from the NUE model

The model departs from the new urban economics (NUE) by allowing a single economic agent (a G-agent, e.g., a corporate headquarters) to contact every location with equal frequency: the G-agent is allowed to travel in every direction. A NUE-like assumption requires all other agents to contact the G-agent, in which case, the G-agent must locate at the center; i.e., the CBD is necessarily endogenous. The evolution of subcenters begins with growth in demand which raises the level of bid rents by enough to outbid agriculture. After one agent moves to the suburbs, interdependency among agents insures that the incipient suburban center becomes more attractive to other agents.     

A simple method for concentrating and detecting viruses in wastewater

A simple method has been developed for routine analysis of sewage and sewage effluents for detecting viruses using adsorption at pH 3 on a 0·45 μm 47 mm diameter membrane filter and elution at pH 8. It was tested on viruses added to autoclaved sewage. Homogenizing the sample for 4 min in a Waring blender and clarification by centrifugation at 1800 g and later at 9230 g facilitated easy filtration without any loss of virus. Retention of the eluant for 30 min on the millipore membrane and then elution in situ under suction provided a sterile eluate with 100 per cent recovery of viruses.

Viruses added to fecal suspensions with 600 mg I⁻¹ BOD were completely recovered when the sample pH was adjusted to 3 and its salt concentration increased by adding 1200 mg l⁻¹ of Mg²⁺ as the chloride. This procedure eliminated the need for passing the samples through ion exchange resins for removing membrane coating components. In a 1 yr programme of monitoring of raw sewage from a middle income group community in Nagpur, a maximum of 3150 PFU/1 during monsoon and 11575 PFU/1 during winter was obtained.

High efficiency and reproducibility of the method allowed the use of sample volumes of 40 ml of raw sewage and 320 ml of treated effluent for the detection of viruses.     

A simple unified stress-strain model for geotextile-wrapped soils

The stress-strain behaviour of geotextile-wrapped soils is a matter of great concern in geotechnical engineering practices. In this study, a unified stress-strain model for geotextile-wrapped soils is proposed and is applied to understand the strength and deformation characteristics of soilbags (woven bag-wrapped soils) in 2D biaxial loading. It is demonstrated that the strength of wrapped soils is greatly improved due to the wrapping effect, and the shearing contraction of the wrapped soils is more pronounced than that of the pure soils. The validity of the results is verified through numerical simulation using the discrete element method (DEM). The effect of the geometric size and material properties of the woven bag on the strength and deformation characteristics of the soilbags is also analyzed using the proposed model. The proposed model differs from existing phenomenological models in that it is able to predict the mechanical response of soilbags when the constitutive behaviours of the wrapped soils and the woven bag are given.     

一种机口简易可靠的供油装置

我们认真学习了<砖瓦>2003年第11期曹世璞<使用油机口的技术要点>和<砖瓦>2001年第1期颜志武<挤泥机机口的油润滑技术>两篇文章.结合我们的实践,找出一种利用多缸柴油机高压油泵装配机口油润滑供油系统的方法,现奉献给各位砖瓦同仁.     

Conditions for obtaining and electrochemical properties of thermochemical and magnetite anodes

We studied the conditions for the formation of a magnetite anode by thermal decomposition of iron nitrate. It has been found that the magnetite samples obtained from pure nitrate possess low stability in operation and electrocatalytic activity. Introduction into the composition of the active coating of alloying additions of copper, cobalt, manganese, and molybdenum makes it possible to improve electrochemical properties of magnetite anodes. It has been shown that in terms of stability and electrocatalytic activity thermochemical anodes surpass plasma-evaporated ones.     

A simple simulation method for river self-purification studies

A simple simulation system is described for the study of river self-purification processes. A linear relationship between the organic load and the critical deficit on the sag curve was obtained for each temperature, corresponding to 36–52 per cent assimilation. The rate is not constant, and the monomolecular theory is not suitable to describe the results. Two distinct phases are observed. Nitrification appears as a second and distinct sag in the oxygen curve. It is limited by oxygen transfer and equilibrates at an O₂ tension of 0·6–1·05 mg 1⁻¹.     

A simple respirometric technique for assessing compost stability

Stability is an important compost quality characteristic, but also one that is difficult to measure. A simple respirometric technique for the assessment of compost stability (SOUR test) was developed, that utilises a dissolved oxygen probe to measure changes in the oxygen concentration in an aqueous compost extract, under conditions ensuring optimum microbial activity and maximum reaction rates. A fully automated procedure is described and possible problems are discussed. The method was used to follow changes in stability of sewage sludge composts from a commercial plant using the windrow composting system. Two different batches of material were monitored. Results were compared with three other stability tests, a respirometric method utilising solid compost samples and the COD and optical density of compost water extracts. Both respiration tests indicated increasing compost stability with processing time and gave significant correlation both with compost age and with each other. The SOUR of the raw mixture was different for the two batches (9.3 and 18.4 mg O₂/g VS/h), but after composting and maturation both dropped to about 1 mg O₂/g VS/h. Measuring the respiration rate of an aqueous compost suspension rather than a solid compost sample offers certain advantages: the test is not affected by variations in the matric water potential of the samples; there is immediate contact between substrate, microbes and oxygen leading to maximum reaction rates; and the gas–liquid barrier for oxygen diffusion at the surface of the compost particles is omitted. The COD and the optical density of the water extracts did not show clear trends and did not allow any conclusions about compost stability to be drawn.