Pond systems

The need for redundancy in the culture system needs to be assessed. Failure of a well pump that brings up water to supply a static pond system may not be a serious problem in countries where new pumps can be purchased in a nearby town. However, it can be disastrous in developing countries where new pumps and pump parts are often not available, but must be ordered from another country. Several weeks or months may pass before the situation can be remedied unless the culturist maintains a selection of spares. 

J. F. Hagman, Ponding Systems for 1A4AE4C, Bulletin E-36062, Du Pont Polymers, Stow, Ohio, July 1980. 

Primary treatment and secondary treatment are also cosdy. Where appropriate, therefore, the millions of dollars spent on wastewater treatment might be shifted to alternative methods of waste management, such as advanced integrated pond systems, which are described next. 

ADVANCED INTEGRATED POND SYSTEMS TREAT WASTEWATER... 

The advanced integrated pond (AIP) system, shown in Figure 16.24, is a method of wastewater treatment that makes sense for many communities of 2000 to 10,000 people in both developed and developing nations. Wastewater is channeled into an extensive pond system where plants use nutrients from the sewage as fertilizer. A system of paddlewheels guarantees constant aeration of the effluent,... 

The pilot advanced integrated pond system in St. Helena, California, which has been in operation since the 1960s. There are now more than 85 AIP systems in operation in various spots around the world. 

What is the source of the energy used to aerate wastewater in an advanced integrated pond system ... 

Advanced integrated pond systems to date are best suited for small communities that have access to wide areas of land and lots of sunshine. But even if the conditions are right for a particular community, there is still the social inertia to overcome for doing something different. 

Combined Dry Tower-Cooling Pond Systems for Power Plant Cooling... 

Figure 8. Schematic flow diagram for ponding system (28).

Therefore it is very common to find islands of solids floating in the anaerobic ponds. This often results in dead spots and short-circuiting in the ponds, which reduces the treatment efficiency of the system. Obviously it is very labor intensive and expensive to maintain the ponding system in very satisfactory conditions. It is also imperative to ensure that as little oil as possible is allowed to get into the anaerobic pond. Otherwise the oil will agglomerate with the rising solids brought up by the biogas and form a sticky scum that is difficult to remove. It is not advisable to allow excessive accumulation of the scum so that the effectiveness of the system is not adversely affected. 

As compared to the ponding system, the scum and solid buildup in the digester can be readily monitored and controlled. 

FIGURE 10.1 Flowsheet for the electric furnace process for the production of elemental phosphorus. Phossy water from the phosphorus phase separator (sump) is normally maintained in a closed-circuit holding pond system which also provides the feedwater for the phosphorus direct contact condenser. Some facilities have a further indirect, heat exchange condenser for the carbon monoxide stream, after the direct contact condenser. 

The physical reaction of the ash to aqueous leaching is an important factor when considering the potential contamination of groundwater by these leachates. Concentrations of elements in leachates will be determined by the amount of ash exposed to leaching solutions. Observations of this type are useful in determining the mode of disposal most suited for the ash being produced. For example, the WYO-FA sample would be better suited to a dry disposal system, with an occasional wetting, rather than the pond system which is most frequently used. 

The effect of single applications of esfenvalerate [S-alpha-cyano-3-phenoxybenzyl (S)-2-(4-chlorophenyl)-3-methylbutyrate] was examined (Lozano et al 1992) in a pond system containing plant and animal communities including the following macrophytes and phytoplankton, micro- and macroinvertebrates and fish (fathead minnows, bluegills, and northern redbelly dace (Phoxinus eos)) which were placed in enclosures. A range of toxicant exposure concentrations was employed, but at the lowest that were used, the concentrations of the toxicant were unmeasurable after 24 h. 

The author, in association with W. J. Oswald, over the past four years has studied lower cost algal production and harvesting systems for application to both wastewater treatment and energy production (26-28). The research has concentrated on the problems of microalgal harvesting and species control in experimental and pilot-scale sewage high-rate pond systems. The first... 

Table V shows the effect of wastewater treatment level on the cost-effectiveness of a hypothetical 1-MGD algae pond system in Greensboro. NC, as a base case. Cash flow decreases as the level of treatment increases. For...

The algae pond system developed for the base case was applied to each of the 15 candidate PEF sites using local data. The major factors which influenced the relative value of the cash flow at the different sites were months of operation, the level of treatment, and the plant size. Higher levels of treatment result in lower net annual cash flows and increasing capital cost. The results of the site-specific performance runs indicate that, for the present, a carbon-limited, secondary treatment system will be most cost-effective. 

---