Direct solar radiation data as input into mathematical models describing the thermal performance of buildings—I. A review of existing relationships which predict the direct component of solar radiation

Solar radiation is not commonly recorded in the meteorological network and it is therefore generally necessary to predict its value theoretically. The majority of solar radiation predictive methods assume a standard atmosphere. Thus they are of limited application to ‘all-year’ thermal design models. A review of the nature of direct solar radiation and methods by which it can be predicted are presented.     

Dynamics of the ozonation of phenol—II mathematical simulation

Several investigators have described the rate of ozonation of phenol in an ozone contactor by empirical equations which are system-specific and are limited in their applicability to other systems. In this paper, the rate of mass-transfer of ozone, the oxidation kinetics of phenol and the kinetics of formation and oxidation of the intermediates have been incorporated into a mathematical model which provides a more accurate picture of the process of oxidation of phenol by ozone under dynamic conditions.     

Experimental determination of thermal performance of glazed façades with water film,under direct solar radiation in the tropics

An experimental investigation of a glazed façade oriented west has been conducted utilizing the Sustainable Glazed Water Film (SGWF). The experiments involved the following three parameters namely: the water flow rate, the type of glazing, and the solar radiation intensity. Two full-scale rooms were used, one as a reference room, with a fixed configuration, and the other as a test room, which could be configured in different ways. The ability of the SGWF to reduce the passage of the solar energy during the sunny hours and hence to limit the heat passage through glazing was analyzed. The aim of this paper is to examine the improvement in thermal performance obtained by the flowing water film over glazed façades. It has been found that the flowing water film on the glazed façade lowers the glazing surface temperature by 7.2–14 °C (average) and absorbs a portion of the solar energy resulting in decreasing indoor temperature by 2.2–4.1 °C (average). However, with increased solar radiation intensity, the SGWF provides a better level of efficiency in reducing the heat transfer indoors.     

Soil/cement as a walling material—II. Some measures of durability

In the first paper a full factorial experiment designed to investigate changes in strength and strain characteristics was discussed. The main factors in the experiment involved changes in soil type, cement content and compaction pressure. This paper discussed the results from the same experiment using two measures related to durability as criterion variables. The first measurements recorded were of the initial surface absorption values and the second from a simplified freeze/thaw cycle test.     

MATLAB modelling and examination of the effect of heat capacity of basin and glass cover on performance of solar still by thermal models

There are numerous researcher-developed mathematical models for single slope passive solar stills which considered the effect of heat capacities of basin and glass cover as negligible. The negligence parameter also plays a vital role in the prediction of the thermal performance of the system. In this paper, an effort has been made to evaluate the cumulative yield, energy efficiency and exergy efficiency of a single slope passive solar still with and without considering the heat capacities of basin and glass cover by using various thermal models such as Dunkle’s model, Zheng Hongfei et al.’s model and Tsilingiris model. These models were studied and compared with and without considering the heat capacity of solar components such as basin and glass cover. The thermodynamic model of this system is developed, and executed in a MATLAB code. By comparing the theoretical values of the cumulative yield, energy efficiency and exergy efficiency, it was found that consideration of the heat capacities of glass cover and basin gives a higher output in all the thermal models.     

The effect of reactor hydraulics on the performance of activated sludge systems—II. The formation of microbial products

A new model involving the concept of soluble residual microbial products formation was used to investigate the effect of reactor hydraulics on the substrate removal efficiencies of activated sludge systems. Strong experimental evidence in the literature suggests that what is measured in most studies is not the remaining portion of the influent degradable substrate, but organic matter of microbial origin which is residual, at least for the operating conditions considered. An appropriate simulation approach was formulated to account for the formation of these products, by a simple mechanistic modification of the newly proposed task group model. This model showed no practical difference between the performances of completely mixed and plug flow activated sludge systems, because they produced almost equal amounts of these microbial products, under similar operating conditions.     

Construction of the Seikan undersea tunnel—II. execution of the most difficult sections

This paper describes the three main problems associated with the difficult sections of the work which were encountered and for which solutions were found during construction of the Seikan Tunnel: (1) the excavation of squeezing ground; (2) water inflow accidents; and (3) the excavations of unconsolidated zones. Squeezing ground, which appeared in the F-10 fault with an earth pressure as high as 2 MPa, was excavated employing spring line drifts and the short bench method with steel pipe supports filled with reinforcing hoop-shaped steel bars and grouted with a high-strenth mortar. The most serious water inflow incident (maximum rate of 70 m³/min.) occurred in the service tunnel on the Hokkaido side in May 1976, causing inundation of 3 km of the service tunnel and 1.5 km of the main tunnel. By correctly judging the situation and making strenuous efforts over the next 5.4 months, the remedial work—which included water drainage—was safely completed. There were no fatalities or serious injuries resulting from the accident. The unconsolidated soft sand layer of the Kuromatsunai Formation, which existed in the middle of the Tsugaru Straits, was excavated without any water inflow accidents. This was accomplished with the aide of water-seal grouting and by carrying out construction procedures with care. Although different measures were required for each problem, the difficulties were overcome by careful investigation and construction management.     

Automatic control of the activated sludge process—II. Efficacy of control strategies

Through the use of computer simulation, the efficacies of the following strategies for control of the activated sludge process were evaluated: single loop feedback control; multiple loop feedback control; single loop feedforward control; feedforward/feedback control; and multiple loop feedforward control. The best improvement in system performance was found with multiple loop feedforward control although the full benefits of the technique could not be achieved due to saturation of the manipulated variables. During the research two types of plants were simulated: Case I in which the concentration of suspended solids in the final effluent decreased as the MLSS concentration entering the settler increased, and Case II in which the effluent suspended solid increased. The best choices for the measured and controlled variables in the multiple loop feedforward control systems depended heavily upon the type of behavior exhibited by the final settler.     

Persistence of some phenylamide pesticides in the aquatic environment—II. Adsorption on clay minerals

Adsorption of IPC, CIPC, Linuron, Neburon and Vitavax on bentonite clays (H-, Fe- and Ca-forms) was investigated. Adsorption was found to conform with Freundlich's equation and to depend on the nature of saturating cation as well as the chemical structure of phenylamides. Considerable amounts of bentonite are needed to bring about effective removal of these pesticides from polluted water. The role of suspended clay minerals in the decontamination of surface waters will be rather limited.     

Mathematical analysis of the chemical system “cyanide-heavy metals” in water—determination of components and toxicity of the system—II. Solution by computer

An essentially new method of chemical analysis was developed and named “the non-experimental chemical analysis”. The subject of the method is the qualitative and quantitative analysis of chemical properties of the system of complex forming reagents and central atoms. The method is based on the application of the general system equation. An application of the general system equation for the toxic system “cyanide-heavy metals” in water solutions is advanced.     

Automatic control of the activated sludge process—I. Development of a simplified dynamic model

A set of simplified dynamic models was developed for the activated sludge process (primary settler, biological reactor, and final settler). The models incorporate variable gains, variable time constants, and fixed dead times. Because the parameters may be easily evaluated on site, the models will be particularly useful for process analysis, control system design, and automatic control of a particular plant. Two different cases were studied; one for a plant in which the steady state concentration of suspended solids in the final effluent is directly proportional to the mixed liquor suspended solids, and one in which it is inversely proportional. Due to this difference in steady state gains the final performance of the system is quite different for the two cases although the dynamics are very similar. Therefore, care should be taken in characterizing the final settler.     

The effect of reactor hydraulics on the performance of activated sludge systems—I. The traditional modelling approach

The traditional modelling approach involving only overall substrate and biomass parameters and a Monod-type of a rate expression was used to investigate the effect of reactor hydraulics on the substrate removal efficiencies of activated sludge systems. The traditional kinetics was observed to give a useful, although not a completely accurate picture of performances of different types of reactors: it showed basically that the relative performance of a given hydraulic configuration was significantly affected by the kinetic constants as well as by operating parameters. The results of model simulations indicated that most experimental studies in this area, were designed to operate at a range which should secure complete removal of the growth limiting substrate; therefore, the related experimental data so far available, do not necessarily provide conclusive evidence on the effect of reactor hydraulics.     

Organic desorption from carbon—II. The effect of solvent in the desorption of phenol from wet carbon

The desorption of phenol from active carbon was studied using cyclic and continuous flow desorbers. A wide difference in desorption capabilities was shown among ten solvents. The system employed was complex, with water being present in addition to phenol on the carbon. An attempt to correlate the desorption data with the physical properties of the phenol and solvent and regular solution theory is made. A thermodynamic approach using the linear free energy—enthalpy relationship produced a reasonable correlation of the heat of formation of the phenol—solvent hydrogen bond with the desorption data. This indicates that the desorption of the phenol from carbon in this complex system is dependent upon the ability of the solvent to form hydrogen bonds with the phenol.     

Growth of blue-green algae in the Manukau (New Zealand) oxidation ponds—II. Experimental studies on algal interaction

Water sampled from the Manukau oxidation ponds between 6 December 1973 and 12 July 1974 was tested for its ability to support blue-green algal growth. A local blue-green algal isolate of Anabaena grew well on membrane filtered pond water throughout the year, however the unfiltered water sustained Anabaena only when the resident green algal populations, in particular Chlorella, were low.Temperature and pH optima for growth of Anabaena and the Manukau pond algal dominant, Chlorella, were found to be significantly different: 28–35°C and pH 9–10 and 23–28°C and pH 7–8 respectively. The ambient conditions of the ponds favoured growth of Chlorella over blue-green algae during the period of study.     

Degradation of the herbicide 2,4-D in river water—II. The role of suspended sediment, nutrients and water temperature

The rate of 2,4-D degradation in the Avon River was related to the nutrient concentration, sediment load and dissolved organic carbon content of the water. Addition of sediment and inorganic nutrients increased the rate of 2,4-D degradation, however addition of actively involved organisms did not. This indicates that the rate of 2,4-D breakdown was dependent upon the nutrient status of the river and not the availability of organisms capable of degrading the herbicide.

During the winter, when the river flow rate was at its peak the water temperature was well below optimum for bacterial activity. It is therefore likely that an appreciable amount of 2,4-D washed into the river during winter will eventually be transported into the river estuary.     

The influence of nitrilotriacetic acid on heavy metal transfer in the activated sludge process—II. At varying and shock loadings

In laboratory simulations of the activated sludge process, the impact of shock loads of the detergent builders sodium tripolyphosphate (STPP) and nitrilotriacetic acid (NTA) on the transfer of heavy metals to the effluent, has been studied. Experiments have also been undertaken in which the influent concentration of each builder was doubled, in an endeavour to simulate the effect of a “wash day”. It is apparent from the data presented that NTA, when present under either of these conditions, resulted not only in deterioration of metal removal by the activated sludge process but caused a mobilisation of heavy metals from the sludge. Copper and lead were the metals most extensively affected. The mobilisation of heavy metals from the mixed liquor to the effluent in activated sludge units acclimated to NTA, upon a doubling of the influent NTA concentration, resulted from a failure by the activated sludge unit to completely degrade the additional NTA. The concentration of NTA in the effluent rose to 4.7 mg l⁻¹ following the increase in influent concentration. Ten days were required before effluent NTA concentrations returned to values equivalent to those prior to the increase in influent concentration. When condensed phosphates were added as shock load or upon the doubling of their influent concentration only the removal of copper was adversely affected.     

Cobalt interference in the “non-steady state clean water test” for the evaluation of aerator equipment—II. Occurrence and magnitude for various natural water systems

Water soluble and insoluble oxidizing compounds are formed during the non-steady state clean water test in certain natural water systems causing interference with Winkler dissolved oxygen determination. This results in pseudo high oxygen transfer efficiency of aerator devices. The interfering precipitate consists mainly of hydrated cobaltic oxide. Evaluation of the electrochemical-oxygen equivalent measurements made the presence of hydrated cobalt dioxide in the precipitate plausible. The presence of hydrogen peroxide in the filtrate suggested the formation of peroxodi- and peroxomono-sulfuric acid during the reaeration step. The pH along with the buffering capacity of a test water are the most critical water quality parameters directly affecting the magnitude of the cobalt interference. At pH values of 6.9 and below the cobalt and peroxide interference in the non-steady state clean water tests can be eliminated. Maximum cobalt interference was found to occur at pH values of 10–11.     

A theoretical study of factors influencing the microbial population dynamics of the activated-sludge process—II. A computer simulation study to compare two methods of plant operation

The effects of operating a plant with a constant sludge-wastage rate and with a constant concentration of mixed-liquor solids have been investigated by computer simulations. From a theoretical point of view, if any sewage parameter is not completely stable then a slightly better quality effluent is likely to be achieved when the plant is operated with a constant specific wastage rate. In practice, however, the slight improvement is not likely to be measurable. The effects of a sudden stable increase or a “slug dose” of sewage substrate and bacterial content on the plants operated in the above two ways have been simulated together with diurnal variations in sewage flow, and in the concentrations of bacteria, debris, and substrate in the sewage.