CS203447B1 - Method for transforming aluminous sludge into form once again usable for treatment of water - Google Patents

Description

2G34 «7 (11) IB1) (51) Int. Cl3-C 02 F 11/00 (75)

Author of the invention MELICH IVO, OSTRAVA (54) Method of transferring aluminum water sludge to a water-reusable form 1

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for the recovery of sludge water sludge in water treatment plants whose treatment for drinking water consists of coagulation with aluminum sulfate.

The ever-increasing consumption of drinking water is increasingly covered by surface sources. The quality of these waters differs from the underground mostly by lower hardness, salinity and higher content of organic matter, which is reduced at most water treatment plants by aluminum sulphate dosing and removal of resulting sus. -pendant substances in one or two steps. The cost of aluminum sulphate is one of the largest items in water treatment plants. Aluminum water sludges formed by the hydrolysis of aluminum sulphate and hydrated aluminum oxides and organic and inorganic water impurities are difficult to process on all treatment plants. Calcium hydroxide is dosed on these water treatment plants to adjust the pH, or, together with carbon dioxide or sulfuric acid, is used to cure water. Water hardening is rarely done, because it is a significant economic requirement.

Reducing the consumption of chemicals and, at the same time, improving the workability of the sewage sludge, is a method according to the invention such that sludges from sedimentation tanks, clarifiers and filter washings

S is adjusted in sludge thickening tanks to a concentration of 0.5 to 4 g of dry matter / l. The slurry is added with constant agitation of the calcium hydroxide in the form of lime milk or water in the ratio of dry matter: Ca (OH) 2 = 1: 0.4 to 1. After half an hour of reaction, the remaining, unreacted, sludge can be separated by sedimentation and recovered the aluminum-calcium solution is fed back to the water treatment plant with fresh aluminum sulphate. In the case of very soft waters - up to 0.7mmol / l and uptake and treatment of all suspensions, up to 60% of aluminum sulphate can be replaced in this way. Remaining, unreacted - unlike the original ones, they are easy to use and agriculturally usable. As a rule, when treating raw water with a higher pH value than 6.7, it is advisable to add acid to prevent the penetration of Al 3+ into the drinking water. Example

The water treatment plant in Podhradí prepares surface water from the Kružberk valley reservoir by coagulation filtration, with an average dose of 12 mgAl2 (SOa) 3 X 18 H2O / I and adjusts the pH by dosing calcium hydroxide with an average dose of 11 mg Ca (OH) 2 / 1. Water production is 1850 1. s_1. Annual consumption of aluminum sulphate 203447

Claims (1)

203447 3 is 680 t, calcium hydroxide 650 t, the annual production of sludge is about 400 t of dry matter. Sludge is thickened in sludge thickeners and dried in sludge fields. The daily production of sludge dry matter is on average 1.1 t, when processing sludge with 1 g of dry / 1 it is easy to process 1100 m3 of diluted sludge. The daily consumption of calcium hydroxide is 60%. to sludge dry matter, i.e. 0.65 t, which is about 40 percent of the current dose. So, every day, it is necessary to prepare 6.5 m3 of lime milk with 100 g of Ca (OH) 2/1, which is added to the prepared sludge after stirring. the alumina solution obtained in the sludge field will be pumped back to 12 liters s -1 back to the feed lines. The resulting coagulant replaces annually 2701 aluminum sulphate with increased consumption. This is the amount that remains in the undissolved form in the excess. The process according to the invention can be applied to all water treatment plants treating soft surface waters using aluminum sulphate. The highest economic benefits will be those with a hardness of up to 0.7 mmol / l with a pH of up to 6.5, where it will not be necessary to adjust the pH with an additional acid feed. The closest operational implementation is at those treatment plants where facilities are available to prepare calcium hydroxide additions to the water of the thickening tank, which can be used for this purpose at the same time. The existing equipment will have to be supplemented by dosing of calcium hydroxide into the sludge, pumping the recovered solution back to the treatment plant and the like, obtained by mixing waste aluminum sludge with a dry matter content of 0.5 to 4 g / l of calcium hydroxide in the ratio - · dry matter : Ca (OH) 2 · · 1: 0.4 to 1. Sevorography, np, race 7, Most