Ismail I. Esen

Algae removal by sand filtration and reuse of filter material

Abstract Integrated pond systems consisting of facultative and high-rate ponds operating in series can produce an effluent low in dissolved organic material, nutrients, and hazardous bacteria. However, the effluent is rich in algae, and cannot meet stringent water-quality criteria on suspended solids. The algae, therefore, must be removed before final discharge or reuse of the effluent. This study reports on the efficiency of slow sand filtration in removing algae from high-rate pond effluents. When agricultural sandy soil with an effective grain size of 0.08 mm was used as the filter medium, an average filtration rate of about 1.3 m 3 /m 2 .d was obtained. If filtration was preceded by sedimentation, the duration of a filtration run was about 100 h. At the end of each run, the filter was cleaned by scraping off the top few centimeters of the filter bed. The filtered effluent consistently had a biochemical oxygen demand (BOD) value less than 20 mg/L and undetectable fecal coliforms. The filter media, being rich in organic matter and having moisture-retaining properties, can be used as a soil conditioner.

ESTIMATION OF GREEN-AMPT PARAMETERS FROM INFILTROMETER DATA

The Green-Ampt equation developed early in this century is regaining popularity in describing the infiltration of water into the soil as a function of time. The parameters defining the Green-Ampt equation have physical bases, and they can be determined from the physical properties of the soil. However, small variations in the Green-Ampt parameters may result in large deviations in the predicted values of the cumulative infiltration. In this report, I present a nonlinear least-squares scheme for estimation of the hydraulic conductivity, K, the product of available porosity, n, and the capillary pressure head, &phis;t, which appear in the Green-Ampt equation. The method developed requires only infiltrometer data on cumulative infiltration measured at specified times. Four case studies investigated show that, in general, the method calculates the hydraulic conductivity lower and the capillary pressure head higher than do methods reported in literature.

Physical model study of thermal and chemical pollution in the Shuaiba offshore area of Kuwait

Abstract The cooling and process waters of the industrial plants located in the Shuaiba Industrial Area in Kuwait are supplied by a complex system of seawater outlets and intakes. Discharge of heated water from the industrial plants is considered a major problem since it may recirculate directly through the intake towers, and the cooling water withdrawn may be at a higher temperature than is desirable. Higher cooling water temperature reduces the efficiency of industrial plants and causes thermal pollution, which adversely affects the water of the Arabian Gulf. In addition, the discharged process water may cause chemical pollution in the offshore area. An undistorted physical model with a scale of 1:50 was constructed and tested with the basic objectives of determining the temperature field in the Shuaiba offshore area identifying possible recirculation patterns and temperature increase at the intake, examining the flow and mixing characteristics of chemical effluents discharged, and investigated alternative remedial measures. The model test results showed that, in line with the field tests, the temperature of the sea water at the intakes was about 1.7–2.5°C higher than the ambient temperature. When heated water from the larger outlets was allowed to discharge into a channel running parallel to the shoreline and curved to stay parallel to the outside of the southern breakwater of the Shuaiba harbor, the temperature increase at the intakes was limited to 0.8–1.0°C and tests showed that the concentration of conservative chemical pollutants at the intakes was reduced by about 50%.

Energy Loss at a Drop Structure with a Step at the Base

Abstract The flow over a drop structure placed in a rectangular channel was investigated through an experimental program. It was noted that the downstream depth of flow was crucial to the formulation of the problem. Two procedures were developed for the estimation of the downstream depth. The first procedure was physically based with an empirical component for the estimation of the depth of the pool formed at the base of the drop. The second was a purely empirical procedure, which resulted in an equation for the direct estimation of the downstream depth. The parameters of the equation were determined by least-squares techniques. Both procedures resulted in reasonably accurate estimates of the downstream depth. The energy loss at the drop was then calculated and compared with the results of previous studies. The investigations were repeated with a single step placed at the base of the drop. It was observed that the step significantly increased the energy loss at the drop.

Bod and cod removal in waste stabilization ponds

Two identical facultative ponds were operated in parallel under the same environmental conditions with the same sewage supply. While one pond was operated as control at fixed depth and constant sewage inflow, the hydraulic conditions for the other pond were varied. It was observed that the BOD and COD removals in the control pond varied almost linearly with areal loading at all times. On the other hand, BOD and COD removals exhibited distinctly different patterns in the variable pond.

Rotary biological contractor operation with water action

A model rotary biological contractor (RBC) system was developed such that rotation was achieved by the weight of the influent sewage and recycled treated wastewater. The RBC system developed was intermittently fed by raw sewage 8 h/d. Results of the investigations showed a significant reduction in biochemical oxygen demand (BOD). The dissolved oxygen levels were higher, and power requirements were lower than conventional RBC systems. The recommended values for hydraulic loading and rotational speed are 0.035 m3/d·m2 and 2 rpm, respectively. The corresponding organic loading was about 0.01 kg/d·m3 as settled BOD.

Generalized Horton Model for Low-Intensity Rainfall

Abstract The Horton equation, which is widely used to predict infiltration of water into soil, is inapplicable when the rainfall intensity is less than the initial infiltration capacity of the soil, especially during the early stages of a storm event. This study modifies the Horton equation to satisfy this condition by considering the rainfall intensity as an independent variable in addition to the other physical parameters used in the original model. The modification is based on dividing the entire infiltration relation into two curves intersecting each other at the ponding time. The two curves are then matched asymptotically into a composite relation that does not require implementing the ponding time parameter explicitly. The proposed relation satisfies the infiltration capacity of the soil such that, when ponding occurs, the difference between the potential and cumulative infiltration becomes zero. This agreement suggests that the proposed relation would be valid for describing the infiltration process within a wide range of rainfall intensities greater or less than the infiltration capacity. The proposed relation will be useful to extend our ability for understanding hydrologic processes related to rainfall infiltration in arid and semiarid environments.

Least-squares estimates of the Horton infiltration parameters

The well-known Horton equation is still one of the most frequently used models defining the infiltration of water into soil. The Horton equation has been criticized because it has no theoretical basis, and because direct analytical methods are not available for the determination of the three parameters defining the equation. This paper presents a nonlinear least-squares scheme for estimating the initial infiltration rate, fo, the final infiltration rate fc, and the rate constant, K, which define the Horton equation. For the four case studies investigated, the performance of the Horton model in estimating the infiltration volume was observed to be excellent.

Transient versus steady state testing of thermal jets in the near field - a case study

Two undistorted physical models at scales of 1 : 100 and 1 :50 were built to investigate the hydraulic and thermal properties of the Shuaiba nearshore area in Kuwait. The models reproduced the southern breakwaters of the Shuaiba harbor and the three cooling water intakes and five heated effluent and process water outlets. The 1 : 100 model was operated at frozen tidal levels under steady-state conditions. In the 1 :50 model, transient conditions were simulated, allowing the tidal levels and currents to vary over one complete tidal cycle. The models were constructed in the 56 x 37 m basin of the Hydraulic Laboratory at the Kuwait Institute for Scientific Research (KISR). Tests results indicate that the temperature differential isotherms determined at frozen tidal states are significantly different from those determined under transient conditions.