Novel Design Concept for Facultative Ponds Using Rock Filters to Reclaim the Effluent

This paper presents a novel design concept for using rock filters as in-line natural media in waste stabilization ponds. A pilot-scale algae-rock-filter pond (ARP) system was investigated in parallel with algae-based ponds (ABPs) over a period of 6 months to evaluate the treatment efficacy of both systems. Each system entailed four equally sized ponds in a series and was continuously fed with domestic wastewater from Birzeit University. The removal rates of organic matter, nutrients, and fecal coliforms were monitored within each treatment system. The results obtained revealed that the ARP system was more efficient in the removal of organic matter [total suspended solids (TSS) and chemical oxygen demand (COD), 86% and 84%, respectively] and fecal coliforms (4log?) than the ABP system (81%, 81%, 3log?, respectively). The ARPs showed higher removal rates for ammonium and phosphorus (68.8% and 50.0%, respectively) compared with the ABPs (57.9% and 41.5%, respectively). The biogenic-aerated ARP option is a cost-effective and land-saving alternative with effluent quality suitable for restricted agricultural irrigation. The ARPs utilizing a new algae-biofilm design concept should be investigated at a large scale to enhance the information available to relevant decision makers, who are seeking sustainable on-site wastewater treatment alternatives.     

Constant flow solar pond collector/storage system

This paper presents a periodic analysis of the process of heat extraction by the brine layer circulating at constant flow rate through the bottom convective zone of a solar pond. Explicit expressions for the transient rate of heat extraction and the temperature at which heat can be extracted, as a function of time, depths of convective as well as non-convective zones and the flow rate, are derived. Extensive analytical results for the optimum performance of a pond during its year round operation are presented. In a pond with an upper convective zone depth of 0.2 m optimum heat extraction efficiencies of 24 per cent, 29 per cent and 32 per cent corresponding to heat extraction temperatures of 89, 55 and 42°C are predicted for water flow rates of 2 × 10^?4, 5 × 10^?4 and 10^?3 kg/s m², respectively. The load levelling in the extracted heat flux as well as in its temperature improves as the flow rate is lowered and the non-convective zone is over sized. An increase in the total depth of the solar pond improves the load levelling in extraction temperature, but influences the extracted heat flux differently; shifts its maximum to winter months and deteriorates the load levelling. The variability in flow rate required for the maintenance of constant temperature of the heat extraction zone is also investigated. It is found that the required variability is less for higher temperatures of the heat extraction zone and larger depths of the non-convective zone.     

Nitrification of ammonia in wastewater: Field observations and laboratory studies

Complete nitrification of ammonia in partially treated domestic wastewater was demonstrated in a mixed culture chemostat. The optimal detention time of water in the chemostat for maximal nitrification was 6–7 days. In the field, a significant number of nitrifying bacteria was present in a wastewater reservoir, as well as in samples of inflowing water from the preceding anaerobic overloaded oxidation pond.     

An experimental study on a modified design compact shallow solar pond

In this study a design of compact shallow solar pond modified from that of Kudish (Kudish and Wof, 1978) is studied experimentally. The difference between this design and that of Kudish is that the water depth is allowed to be changed from 2–15 cm and is not fixed as in the mentioned reference design. The thermal insulation of the cover is installed between the reflector and the inner surface of the wooden cover. In the design of the reference (Kudish and Wof, 1978), the insulation is fixed on the outer surface of the cover, where it will probably be damaged by water, wind, dust etc. Also in our design, the level of water in the bag is measured using a static pressure manometer. The tests were carried out both in winter and in summer whereas they have been done only in summer in the mentioned reference. The results show that the compact shallow solar pond can provide a suitable water temperature to be used for low and moderate temperature applications even in a cold winter and with 10 cm water depth.     

Physics of shallow solar pond water heater

This communication presents a theoretical analysis of a shallow solar pond water heater, which is in good agreement with the experiments of Kudish and Wolf (1979) and the authors. the heater consists of an insulated metallic rectangular tank with black bottom and sides and a transparent cover at the top. After the collection of solar energy during sunshine hours the heater stores a substantial amount of heat because the top glass cover is covered by an adequate insulation in the night. Analytical expressions for the transient rise of temperature of water in the tank have been derived taking into account the appropriate heat transfer processes during day and night. These experimental results as well as those of Kudish and Wolf (1979) have been found to be in good agreement with the theory presented in this paper. the effects of one more glass cover on the top, and of the thickness of the bottom and side insulation and tank depth on the water temperature have also been studied.     

Study of an indian biogas plant with a water pond

To overcome the problem of reduced biogas production, due to low ambient temperatures during the winter months of northern India, a novel concept of a shallow solar pond (SSP) water heater has been put forward and studied theoretically. The pond is proposed to be integrated with the dome of the conventional Indian (KVIC) biogas design. The results of the study show that system is capable of providing hot water upto a temperature of 40°C which, in turn, can be used for hot charging of the slurry besides reducing the heat losses from slurry to the ambient. Simultaneously, it helps in enhancing the slurry temperature from 20°C to 27°C.     

Design Methodology of Free Water Surface Constructed Wetlands

Simple criteria, guidelines and models are established for free water surface (FWS) constructed wetland selection and preliminary sizing. The analysis employs models for FWS constructed wetland design, considering simultaneously the removal requirements and the hydraulics of the system. On the basis of these models, a step-by-step methodology is developed outlining the design procedure for new and performance evaluation for existing FWS constructed wetland systems. This methodology is combined with simple equations predicting the maximum wetland capacity in summer, so as to assist designers in sizing installations in tourist areas with increased summer populations. Furthermore, this methodology is further simplified, based on sensitivity analysis of the unit area requirements for wastewaters of various strengths, and various design conditions and performance criteria. In addition, comparison of the unit area requirements of FWS constructed wetland systems, subsurface flow (SF) constructed wetland systems and stabilization pond systems for wastewaters of various strengths and design conditions, provides designers with general guidelines concerning the preliminary selection between alternative natural treatment systems in areas where the use of natural systems is favored because of their low-cost, simple operation and high removal performance.     

基于广义互补S型公式的我国不同地区蒸发池蒸发量估算

本文利用全国不同地区13个20 m²或10 m²蒸发池数据,验证广义互补S型公式对小型水体水面蒸发估算的效果,并分析了其参数α_HT的变化特征。结果表明,无论采用暖季(4—9月)的数据还是采用全部数据(有蒸发量观测时期的数据),S型公式均能够有效估算大型蒸发池的蒸发量,效果优于采用率定风速函数的Penman公式。利用暖季(4—9月)数据拟合的参数α_HT介于1.00~1.92,均值为1.52,与相对湿度和温度具有显著负相关关系,利用相对湿度确定参数α_HT的S型公式能够有效估算蒸发池的蒸发量。     

基于健康理论的农村河道疏浚规划浅见

基于新农村建设河道治理方面的需求,以农村河塘健康理论来指导河塘疏浚。在对农村河道现状及存在问题进行分析和诊断的基础上,从水资源开发现状和生态保护方面分析了平原区农村河塘健康的内涵。在规划和管理农村河塘方面,提出了较为明确的方向：在开发和保护中,应维持农村河道良性循环状态,从而实现河塘健康,外在表现为服务功能健全、断面结构稳定、水质优良、生态系统健康。