Hydraulic ram pumps and Sling Pumps

F WATER QUALITY AND SUPPLY: McCONNACHIE, WARHURST, POLLARD and CHIPOFYAFigure 2. Yield and comparative adsorption properties of activated carbons.(Note that the first group of four values are derived from 0.2g samples of carbon and the rest from 0.5g samples)teracted this problem and the results shown for the podsin Figure 2 are from carbons treated in this way.The BET surface areas derived from the nitrogen adsorptionisotherms for EH800/30 was 713m 2 /g and afterrinsing, 931m 2 /g (Warhurst, McConnachie et al., in press).Waste productThe composition of the derived gases and condensate hasnot been determined so far but other work on steampyrolysis volatiles from apricot stones and coconut husks(Razvigorova, Goranova et al., 1994) has identified thepresence of derivatives of phenol, guaicol, syringol,resorcinol, free fatty acids and the esters of fatty acids.Unless a use can be found for this material it will have tobe disposed of. Fortunately it is likely to be readilybiodegradable.ApplicationsThe potential applications for activated carbon includethe adsorption of excessive concentrations of iron andmanganese from groundwater, taste and odour compounds,bacterial and viral pathogens as well as thetertiary treatment of wastewaters.Seasonal problems of taste and odour in drinking waterfrom a number of lake sources in Malawi arise from algalblooms, mainly of the species Oscillatoria and Anabaena,which are difficult to remedy and it is planned to assessthe effectiveness of carbon treatment at the BlantyreWater Treatment Works. Current treatment there is asequence of microstraining, addition of potassium permanganateas an algicide and to remove iron and manganese,addition of chemical coagulant, flow through amixing channel then rapid gravity filters. Chlorination isapplied at various points along the pipe distributionnetwork. The filter medium is sand obtained locally.ConclusionsActivated carbons can be produced from Moringa husksand pods which compare favourably with commercialcarbons using a one stage steam pyrolysis process.For husks the most economical process is likely to beat 800 o C for 30 minutes and for the pods, 650 o C for 30minutes.For some applications a rinsing stage of treatment forthe carbon might be beneficial.Further workAspects of the carbon work still to be undertaken are,• power requirements for various combinations of processtemperature and soak time• adsorption capacity of granular carbons after use andregeneration• application of carbon in treating Malawi drinkingwater supplies for removal of taste and odour• maximisation of carbon production.AcknowledgementsThe financial support of the U.K. Overseas DevelopmentAdministration is acknowledged. The authors are alsograteful for assistance and technical support provided bypersonnel of the University of Malawi and the BlantyreWater Department and for the contribution to the work atEdinburgh and Malawi by Henrietta Ridgeon and EmmaPatey as part of B.Eng. project work.ReferencesGergova, K., N. Petrov, et al. (1993). “Evolution of theactive surface of carbons produced from various raw281