The paper acknowledges that water carriage sewerage systems are not always the most appropriate sanitation solution for the disposal of liquid domestic wastes in developing countries. However, where water carriage systems are proposed, the first treatment option which should always be considered is the use of stabilization ponds, because in many instances, they represent the most cost effective and efficient way of treating domestic sewage flows. The paper results from a review of pond systems installed in six countries and concludes that: (i) designs differ widely; (ii) maximum use is not made of anaerobic ponds or the reuse potential of effluents; (iii) pond systems are frequently grossly overdesigned; and (iv) the designs are not responsive to the incremental growth encountered in LDCs. Practical design criteria are given for pond systems over a range of ambient temperature conditions and end use requirements together with notes on start up procedures, operation and trouble shooting. The recommendations are derived in part from the Israeli experience where considerable use is made of treated sewage effluent for irrigation purposes.

Notes in the design and operation of waste stabilization ponds in warm climates of developing countries

During two Atlantic cruises of the German research vessel Polarstern, 1988 and 1989, the concentrations of light nonmethane hydrocarbons (NMHC) in seawater were measured. On the basis of a simple budget analysis, the oceanic mixed layer represents a NMHC reservoir with an internal production and a major loss by emission into the atmosphere. As a consequence, the concentrations of NMHC depend on the rates of ocean-atmosphere exchange: high exchange rates reduce the concentrations and vice versa. With the prevailing transfer velocities the emission rates were calculated according to ocean-atmosphere exchange models. The regional averages of the alkene emission rates vary by 1 order of magnitude. For ethene the maximum value was 5×108 molecules cm−2 s−1. The emissions of the various alkanes were generally below 1×108 molecules cm−2s−1. The total C2-C4 hydrocarbon emissions during both cruises average 6×108 molecules cm−2 s−1, 70 % of which are alkene emissions, with ethene alone contributing 42 % to the total. No indications for enhanced emissions of NMHC at high phytoplankton concentrations or in the proximity to coastlines were observed. Thus we regard the emissions as representative for the mid-Atlantic and the season of the investigations, August to October. The calculated emission rates of the shortlived alkenes are validated by comparison with atmospheric measurements of NMHC. The emission rates are substantially lower than the majority of reported oceanic emission estimates by up to about 2 orders of magnitude.

/pdf/emissions-of-light-nonmethane-hydrocarbons-from-the-atlantic-4wd5tiw668.pdf

Emissions of light nonmethane hydrocarbons from the Atlantic into the atmosphere

Lagooned, secondary effluents as water source for extended agricultural purposes

SUMMARY Recirculation of effluent from final ponds in a sequence of stabilization ponds into the first ponds was used first in South Africa, New Zealand and Israel as an emergency in cases where a series of anaerobic-facultative-aerobic ponds system became overloaded and produced malodors. Such recirculation eliminated anaerobiosis at the surface of the ponds and increased ponds performance. Later, recirculation ponds systems were predesigned and operated as a process by itself, notably the “cartwheel” system at Cape Flats, S.A. and the “half orange” at the Dan Region (Greater Tel-Aviv), Israel. Pilot plant studies at the Technion in Haifa and field studies at the Dan Region Wastewater Treatment and Reclamation scheme described herein showed some of the basic parameters of the recirculation ponds system. A recirculation ratio of between 1.8 to 2.5 was found to give the best results as far as hydrogen sulfide control and BOD removal are concerned. BOD5 loadings of about 400 kg/ha-day on the first pond and 180 kg/ ha-day on the entire system proved applicable. The effect of recirculation in increasing surface layer dissolved oxygen levels and in reducing algae predator activity at the first ponds in the sequence, is shown. The concentration of algae in the various ponds at different seasons was measured. Chlorella remained the predominant alga seconded by Euglena. The advantages of recirculation ponds over regular stabilization ponds as evident by increased loadings, odor control and increased ponds stability and performance is discussed and analyzed.

Wastewater recirculation ponds—pilot plant and field studies

Performance of wastewater stabilization ponds or sewage treatment lagoons is dependent upon pond water temperature. In recent years there has been considerable interest expressed in raising 'pond ' watE£r temperatures in an effort to inprove performance of the treatment process. Solar heat may be one energy source useful in raising pond

Solar heating of wastewater stabilization ponds

Biological and chemical aspects of stabilization pond design.

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Biological and chemical aspects of stabilization pond design.