The treatment and disposal of waste waters from dairies and milk products factories.

  • Great Britain. Water Pollution Research Board
Date:
1941
Catalogue details

Licence: Public Domain Mark

Credit: The treatment and disposal of waste waters from dairies and milk products factories. Source: Wellcome Collection.

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    12] The approximate range of temperature and of pH value of the liquid at each of these positions is shown in Table LX XVIII. TABLE LXXVIII. Conditions of Exposure of Cubes of Cement Mortar in Experimental Plants at Ellesmere ners Temperature of liquid to which cubes were ex- pH value of liquid Position of cubes | Conditions of exposure to which cubes were posed: (° C.) oe Storage and balanc- | Completely im- | Inlet to tank, 10 to | Range, 4:2 to 6-6; ing tank for crude mersed 59 usual value about liquid Intermittently im- | Outlet from tank, 5:0 | mersed 6:5 to 43 | Primary sedimenta- Com pletely im- 6:5 to 39 Range, 4:2 to 6-6; tion tank | mersed usual value about Partially immersed 5:0 see Filter No. 1 Buried about 1} in. 2 to 25 Range, 4:4 to 68: under vsurface of | usual value about Filter No. 2 filtering medium : 5:8 Aeration tank of | Co mpletely im- 6 to 29 Range, 64 to 86; activated sludge mersed usual value about plant, near inlet Partially immersed ) 7:3 In the storage and balancing tank the temperature of the crude milk washings or whey washings was usually relatively high and the liquid was always acid in reaction; the strength of the liquid, as measured by the test for biochemical oxygen demand, was greatest in this part of the plant. In the primary sedimentation tank for crude liquid the strength and #H value of the washings were about the same as in the storage and balancing tank, but the temperature was rather lower. After treatment in the primary sedimentation tank the crude liquid was diluted with purified effluent before distribution on the primary filter. The temperature of the diluted liquid was usually lower, and the pH value was usually higher, than in the undiluted liquid in the primary sedimentation tank. Each of the two filters, Nos. 1 and 2, was used as a primary filter for a period of 2° or 3 weeks; the order of the filters in series was then reversed and the filter was used for a similar period as a secondary filter. The average biochemical oxygen demand of the liquid distributed on a filter in the primary position was about 25 parts per 100,000 parts, though comparatively large fluctuations occurred from time to time; the biochemical oxygen demand of the effluent from the primary filter, which was distributed on the secondary filter, varied from 1 part to 4 parts per 100,000. The average biochemical oxygen demand of the liquid supplied to the aeration tanks of the activated sludge plant was about 50 parts per 100,000, but the biochemical oxygen demand of the liquid in contact with the specimens was less than this, since the incoming crude liquid was diluted by the partially purified liquid in the aeration tanks. The liquid in the aeration tanks was usually neutral or slightly alkaline in reaction. Observations on the condition of the cubes of mortar after exposure for periods of 7 months and 15 months are given in Tables LX XIX, LXXX, LXXXI, and LXXXII. In the storage and balancing tank for crude liquid the cubes of untreated Portland cement mortar were severely attacked, the surface of the mortar being softened and the aggregate exposed, in some cases to a depth of $} in. The attack appeared to be due to leaching and softening, since it was progressive from the surface and did not affect the interior of the specimens. Specimens treated with sodium silicate and magnesium silico- fluoride were rather more severely attacked than were untreated specimens. The tar-base paint was almost completely removed by softening or powdering, but the exposed surface of the mortar had not been so severely attacked as the untreated mortar, since the paint had afforded protection during the early part of the period of exposure. Bitumen-base paint was intact on specimens completely immersed in the liquid, but patches of the paint had been removed from the cubes which were immersed intermittently. Coating with bitumen-base paint appeared to be the most effective of the methods of treatment of Portland cement mortar tried. Specimens of untreated mortar made with aluminous