Aug. 3, 1888.] 



SCIENTIFIC NEWS. 



"5 



SOCIETY OF ENGINEERS. 

 The members of this Society and their friends paid 

 a visit to the new Precipitation Works at Barking 

 Sewage Outfall, on July 24th, 1888. At the 

 present time the whole of the sewage of the 

 Metropolis north of the Thames is conveyed to Barking 

 Creek by three culverts, each 9 feet high by 9 feet wide, 

 and is, in the first instance, delivered into a covered re- 

 servoir divided into four compartments and altogether 

 extending over an area of nine acres. The sewage is 

 stored in this reservoir during eight hours of each tide 

 and discharged into the river at high water at the top of 

 the ebb. This reservoir is situate on the east side of the 

 sewer and immediately adjacent to the river bank. 



The new works consist of covered precipitation tanks 

 adjacent to this reservoir on its north side, and occupy- 

 ing the ground between the Outfall Sewer and Barking 

 Creek, an area of between ten and eleven acres. 

 There will be thirteen of such tanks, each 31 feet 6 

 inches wide and averaging about 1,000 feet long. Com- 

 munications will be made between the Outfall Sewer 

 and each of these tanks, each fitted with two penstocks, 

 so that communication may be opened or shut off at 

 pleasure. 



The sewage will be admitted into each of the tanks in 

 succession, and after being allowed to remain quiescent 

 for a sufficient time to admit of the deposit of the solids 

 in the sewage, the precipitation of which will be expe- 

 dited by the admixture of 3-7 grains of lime and 1 grain 

 of proto-sulphate of iron per gallon, the effluent will be 

 run off over a weir which will fall as the water in the 

 tank lowers, so that the top film of the effluent only will 

 be taken off, and the tank emptied gradually so as to pre- 

 vent any disturbance of the solids by the operation. 



The effluent after flowing over the weirs (of which 

 there will be ten in each tank) will pass into culverts 

 carried transversely under the tanks and extended, 

 some into the compartments of the existing reservoir, 

 and some into a chamber under the Outfall Sewer 

 through which, at present, the sewage is discharged into 

 the river from the existing reservoirs. When the level 

 of the tide will admit, the effluent will be discharged 

 through this chamber direct into the river, but when the 

 water in the river is too high to admit of this the effluent 

 will be conveyed by the other culverts into the several 

 compartments of the present reservoir, and stored there 

 until the level of the water in the river will admit of its 

 discharge. 



When each compartment is emptied of the effluent, 

 the sludge, which will be in a semi-liquid state, will be 

 discharged through culverts passing under the Outfall 

 Sewers into a collecting culvert, from which it will be 

 conveyed by pipes into a receiving well or sump, and 

 pumped into a series of twelve tanks placed side by side 

 and situated between the Outfall Sewer and the river. 

 These tanks will each be 20 feet wide and 140 feet long, 

 will cover an area of over an acre and a half, and, like 

 the precipitation tanks, will be covered so as to prevent 

 nuisance. 



The sludge will be allowed to remain quiescent in 

 them so as to allow of a further precipitation, and the 

 effluent water will be discharged over weirs into a culvert 

 which will convey it into a store under the tanks, from 

 whence it will be lifted and discharged through pipes 

 to the liming station, there to be mixed with lime which 

 is used for precipitation. 



The settled sludge remaining after this further pre- 



cipitation will be discharged through culverts into a 

 sludge store situate under the tanks, and will be lifted 

 thence and conveyed by pipes along a jetty, and to a 

 landing stage to be erected in the river, and there 

 discharged into ships which will convey the sludge to 

 sea. In the event of the ships being detained by stress 

 of weather there is a further store for sludge at a lower 

 level extending under the whole of the area occupied by 

 the upper stores. 



On the north side of these sludge settling tanks will 

 be erected engine and boiler-houses and workshops in 

 connection, to contain engines and machinery for lifting 

 the sludge in the settling tanks, and the settled sludge 

 into the ships, as well as for pumping the sludge effluent 

 to the liming station. 



The lime for assisting the precipitation of the solids 

 of the sewage is introduced in the Outfall Sewers at a 

 point about 700 yards and the proto-sulphate of iron 

 about 530 yards above the precipitation channels. 



The liming station will comprise a lime store, floors 

 for slacking the lime, and six tanks for mixing the slacked 

 lime with the effluent water from the sludge settling 

 tanks or with sewage taken direct from the Outfall 

 Sewers, an elevated lime-water tank or reservoir built 

 above the lime store, and into which the lime-water will 

 be lifted by pumps, for which machinery and the requisite 

 engine and boiler-houses will be erected adjacent to the 

 lime stores. From this elevated tank the lime-water 

 will be conveyed to and injected into the sewage passing 

 along the Outfall Sewers, through cast-iron injectors 

 placed in the sewers. 



There will be means of turning the lime-water into 

 any one of the three lines of sewers and of regulating 

 the supply by means of sluice-valves fitted to the 

 pipes leading to the injectors. The injectors consist of 

 cast-iron chambers 4 feet 6 inches in length, 6 inches 

 wide and 6 feet in height, fitted with a number of 

 nozzles, through which the lime-water will be injected 

 and mixed with the volume of the sewage as it flows 

 past. 



The iron-water station comprises timber sheds for 

 storing the proto-sulphate of iron, a mixing shed in which 

 the iron will be crushed and mixed with water, an 

 engine shed to contain engines and machinery for crush- 

 ing the iron and mixing it with water, as well as for 

 raising water for boilers and into mixing tanks. The 

 iron-water will be conveyed by stoneware pipes, carried 

 underground and along the top of the Outfall Sewer into 

 a service tank, from which it will be carried by pipes 

 into each of the three Outfall Sewers, and injected into 

 the sewage through perforations in a pipe fixed vertically 

 into each of the sewers. As with the lime-water, there 

 will be appliances for regulating the supply of iron- 

 water to each of the sewers, to meet the varying re- 

 quirements of the discharge. 



There will be a large settling pond, covering an area 

 of i|- acre, situate near the river, divided into six com- 

 partments, each 60 feet by 60 feet, and about 7 feet 

 deep, into which water will be received from the river 

 and allowed to settle ; the clear water being afterwards 

 filtered and used for the supply of the several boilers, 

 for slacking the lime, and for mixing with the proto- 

 sulphate of iron. 



The jetty, which will extend 576 feet into the river 

 from the present river bank, will be 15 feet wide, and 

 will be a timber structure supported upon piles. At 

 the river end will be a timber landing stage 300 feet 



