Groundwater recharge with secondary sewage effluent - a study of removal of nitrogen compounds by soil percolation

Groundwater recharge using sewage effluent is becoming very popular. The removal of nitrogen compounds from sewage effluent by soil percolation can be managed by manipulating flooding and drying periods in a recharge operation. The main processes involved in the removal of nitrogen compounds were established as dispersion, adsorption, nitrification, leaching and denitrification. These processes are reviewed, explained theoretically, investigated experimentally and applied to a recharge situation in Perth, Western Australia. The dispersion coefficient was determined by first solving the equation for non-reactive solute transport according to the boundary conditions of a finite column, then comparing this with the breakthrough curve of a miscible displacement experiment. Adsorption of ammonium during infiltration through soil was found to follow a model combining instantaneous and time dependent adsorption rather than either of these alone. Nitrification was described by Michaelis-Menten kinetics for a wide range of values of ammonium concentration. The equation for non-reactive solute transport in porous media was found to explain the leaching of nitrate in soil. Denitrification in soil was found to follow zero order kinetics in the range of concentrations encountered in recharge situations. When recharge is done by flooding and drying the ammonium in the recharged water. is first adsorbed to the soil and then nitrified in the following drying period. During the next flooding period adsorption of ammonium and simultaneous leaching and denitrification take place. Hence an integrated model of all the processes studied separately has been suggested. As an integrated model is difficult to solve with all the variables that are involved, a set of simplifying assumptions have been made and a simplified model developed. The simplified model has been used to explain the results of field experiences reported in the literature, to select soils at a recharge site and to calculate the movement of nitrogen during recharge. In Perth, Western Australia the soil at the recharge, site is Bassendean sand. It was found to be of no use in the removal of nitrogen, so the major soils in the Swan Coastal Plain and a few mixtures of these soils were investigated. Pyrton Sandy Loam and a mixture of Spearwood sand and Pyrton loam were found to be suitable. Pyrton sandy loam was used for further experiments to verify the models proposed for each of the processes and to determine the constants to be used in the simplified model. From the results of these experiment and applying the simplified model further, general conclusions have been deduced for groundwater recharge management

Age and growth of three Indian major carps from Hirakud reservoir

Studies on the age and growth of three Indian major carps viz. Cotlo catlo (Ham). Cirrhino mrigolo (Ham) Dnd Lobeo rahita (Ham) based on scale and the length frequency data are presented. The markings on the sca les of these fishes were used as indices of age, aftar ascertaining the annual nature of formation of growth checks. It was found that in these three fishes rings were laid down almost during the same period i.e. May to August. The fesult obtained from scale study is compared with Petersen Method. A close agreement can be seen in their va lues obtained. Von Bertalanffy's growth equation was used for fitting the growth data obtained by scale study and it adequate ly describe the actual growth of those fishe s. The length at age and the rate of growth of these fishes were compared and it was found that rate of increase in length was faster during the initial periods of life and dec rease when they become old

Anatomical changes during early gonad development in the protogynous greasy grouper Epinephelus tauvina (Forsskal)

Anatomical changes during early gonad development of the culturable species of grouper Epinephelus tauvina was studied. All juveniles developed an ovarian phase initially followed by the bisexual phase gonad. Bisexual phase gonad occurred when the fish was around two years old and in the length range of 188-380 mm total length. The minimum size at first sexual maturation for females was 380 mm total length at an age of two and a half years. The presence of bisexual phase and spermatogenic cysts in juvenile gonads in E. tauvina could be an indication of primary male differentiation. Based on gonadal histological study of E. tauvina till first sexual maturation, it was found that all the juveniles developed an ovarian structure initially and subsequently developed a bisexual phase with male tissue scattered among lamellae, prior to first sexual maturation as females. Although it was not possible to find any primary males among fishes collected from the wild, the developmental significance of a bisexual phase in E. tauvina juveniles is assumed to be similar to diandric protogynous species, having secondary males as well as primary males developed directly from juveniles through sexual differentian

Performance analysis of RTS/CTS protocol over Basic Access in wireless networks

The CSMS/CA protocol is employed in wireless networks in order to overcome issues such as the hidden node problem. This mechanism is expected to handle collisions better using the RTS/CTS mechanism. This method will allow a participating node to take part in communication only if it receives a "Clear to Send" message and thereby, theoretically "avoiding" collision. The objective of this paper is to analyse the improvement that the RTS/CTS mode brings over the Basic Access mode. The paper presents the study of wireless nodes within a specific area with increasing node concentration to verify the performance impact of a protocol in wireless networks, particularly when the node concentration increases

Evaluation of Signal Attenuation for Bluetooth, ZigBee and Sound in Foliage

Rural environments have been struggling to get connected due to various reasons, one of them being the fact that the signal attenuation is too high in foliage, drastically affecting range and power consumption. This study evaluates the effect of foliage in the attenuation of 2.4 GHz signals, namely Bluetooth and ZigBee. An alternate candidate signal, sound is also analyzed in a similar environment. In order to further the experiment, a simulation model using Omnet++ was created and the alpha value, which marks the environmental constant was noted. We have concluded from the study that the signal attenuation for the 2.4 GHz signals are very high in foliage. The high frequency sound signals also suffered drastic signal loss in foliage, but the low frequencies penetrated quite well. Therefore, high frequency signals are poor candidate carrier signals for such environments

Case series of macroalbuminuria and toe-brachial index in type 2 diabetes mellitus

Diabetes mellitus is a growing health problem with a significant global disease burden. The complications and mortality rate associated with diabetes are increasing. Albuminuria is one of its complications and evidence of established nephropathy. Low toe–brachial index (TBI) is more strongly associated with albuminuria and may be a suitable tool for evaluating peripheral arterial disease in patients with type 2 diabetes mellitus. Our study evaluated the association between macro albuminuria and low toe brachial index in type 2 diabetic patients to identify those who need specialized foot care and adequate renal protection

Evaluation of Sound Perception to Identify Candidate Frequency for Wireless Networking ; Chapter In : New Trends in Networking, Computing, E-learning, Systems Sciences, and Engineering

Wireless technology has been introduced and growing since early twentieth century, but there are still environments the current technologies find it difficult to penetrate. The dense jungle terrain, for example, pose a huge challenge for the 0.12 m wavelength of the Wi-Fi signals, but the FM radio frequency signals at a wavelength of 3 m function a lot better. This paper studies the possibility of using a very low frequency, down to the range of audible frequencies to try and identify the frequency band that can be used, ubiquitously and unobtrusively. Sound can be considered as a ubiquitous signal due to obvious reasons and the search is to find the unobtrusive frequency band that can be a candidate frequency for data carrier signals. The paper is presented in two sections, the first section does a geographically and age neutral survey to identify the unobtrusive signal and second section analyses the noise profiles in these frequency band