. Water & sewage works . of the time, butwould not be at all satisfactory as a citysupply without filtration. The sludge disposal system has beenvery effective in preventing the accumu-lation of sediment in the bafiled mixingtank and settling basins. The basinshave been drained for examination and 18 MUNICIPAL ENGINEERING cleaning from time to time and havebeen found to contain very little sludge,except in several instances when someof the drains had become clogged. The Filters The usual burden on the filters islargely removed by the effective settling,and washing the beds is reduced to aminim
. Water & sewage works . of the time, butwould not be at all satisfactory as a citysupply without filtration. The sludge disposal system has beenvery effective in preventing the accumu-lation of sediment in the bafiled mixingtank and settling basins. The basinshave been drained for examination and 18 MUNICIPAL ENGINEERING cleaning from time to time and havebeen found to contain very little sludge,except in several instances when someof the drains had become clogged. The Filters The usual burden on the filters islargely removed by the effective settling,and washing the beds is reduced to aminimum. The average service of a fil- addition of coagulants, but occasionallya very fine turbidity has been encoun-tered, which is extremely difficult of re-moval. Analyses prove this material tobe almost pure silica, and as the condi-tion has always occurred after a rainfollowing a period of highly acid water,it is thought possible that the acidleaches the soluble salts from the mate-rial in the beds of the streams leaving. MAIN WEIR BOX. Mckeesport water purification plant. ter between washings is over 120 hours,and runs as long as 200 hours frequentlyoccur. The per cent, of wash water tothe water filtered amounted to percent, last year, which is remarkably this condition prevails a largepart of the time, there are periods ofvery turbid and alkaline water duringfloods, or even following a heavy shower,when it is necessary to add coagulants,and at such times the work of the filtersIs increased and the length of time be-tween washings correspondingly dimin-ished. The turbidity is usually coarseand easily removed, often without the a skeleton of silica, which is loosenedand washed down by the flood water. Ithas been suggested that sedimentationin the river may be responsible for this,the coarser particles settling out whilethe lighter silica remains in the water is neutral or faintly al-kaline, it is occasionally completely coag-ulated in the river and
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectsewerage, bookyear191
