Treatment of BOF gas cleaning systems sewage sediments by application of flocculants

Many steel-works discharge the sediments from BOF gas cleaning systems sludge pans into the waste accumulators without dewatering, therefore implementation of facilities of their treatment is an extraordinarily actual task. Besides the BOF gas cleaning systems sewage sediments are attributed to a substance rich or relatively rich by iron, which can be utilized in metallurgical production after dewatering. Application of synthetic organic flocculants for sediments conditioning is one of most effective methods of dewatering equipment operation intensification. Results of experiment tests on the treatment of real BOF gas cleaning systems sewage sediment by a high-molecular organic flocculants namely Servey FL9, Nalco 71661 and Nalco 8172 PULV. It was shown, that Nalco 8172 PULV is most effective reagent for the sediment conditioning. The effective doze of high-molecular anion flocculant for treatment of BOF gas cleaning systems sewage sediment before the gravitational thickening and further mechanical dewatering is 0.15 g of active substance per1 kg of dry sediment substance. Technological parameters of dewatering equipment determined when using high-molecular anion flocculant for intensification of the treatment process of BOF gas cleaning systems sewage sediment: the specific load for thickeners by dry sediment substance is 300–400 kg/(h·m2), the specific load for disc vacuum-filter by dry sediment substance is 60–70 kg/(h·m2). Content of suspended particles in bright water from thickeners and filtrate from vacuum-filter is less than 100 mg/dm3.

Problems of modern urban drainage in developing countries

Socio-economic factors in developing countries make it more difficult to solve problems of urban drainage than in countries that are more advanced. Factors inhibiting the adoption of modern solutions include: (1) in matters of urban drainage, 19th-century sanitary philosophy still dominates; (2) both legal and clandestine land settlement limits the space that modern solutions require; (3) contamination of storm runoff by foul sewage, sediment and garbage prevents adoption of developed-country practices; (4) climatic and socio-economic factors favour the growth of epidemics where runoff is retained for flood-avoidance and to increase infiltration; (5) lack of a technological basis for adequate drainage management and design; (6) lack of the interaction between community and city administration that is needed to obtain modern solutions to urban drainage problems. Awareness of these difficulties is fundamental to the search for modern and viable solutions appropriate for developing countries.