Biological Treatment Stage Research Articles

Environmental Impact Evaluation of Istanbul Wastewater Treatment and Marine Disposal Systems

Metropolitan Istanbul Wastewater Treatment System contains 14 marine outfalls, seven of which include secondary stage biological treatment processes. The others have only mechanical treatment units including bar screens and grit chambers. Only one mechanical pre-treatment and marine disposal system, Yenikapi plant, has been operated since 1988 among these 14 plants and six of them are ready for construction. In this paper, the environmental impact of Yenikapi pretreatment and marine disposal system on the water quality of the Bosphorus and the Sea of Marmara has been investigated. Long term water quality measurements which were performed in pre-and post-dischange applications have been evaluated. Water quality parameters including pH, DO, BODs, TKN, P and total coliforms were measured at various sampling stations around the discharge points. A general evaluation of marine outfall systems to be constructed in the scope of Istanbul wastewater treatment project, on the water quality of the Sea of Marmara and the Bosphorus has been presented.

Industrial-Scale Applications of Fixed Biomass on the Mediterranean Seaboard. Design, Operating Results

The technology that consists of treating sewage on submerged granular filters is now far beyond the stages of research and testing on pilot units. Fifteen or so full-scale facilities are in operation in France using, as a biological treatment stage, the fixed biomass technology as realised by the Biocarbone process, particularly for the treatment of sewage from built-up areas along the seaboard. These are cases where the advantages of this technique can be put to decisive use. The Mediterranean seaboard is an ideal site for this technology. Cases in point are the waterworks of Sanary Bandol (pop.60,000) and Perpignan (pop.160,000), that have been in operation for two years and one year respectively. Waterworks in Monaco (pop.100,000) and Antibes (pop.170,000) will be commissioned in 1989 using the same technology. Results obtained during intensive controls show that the fixed biomass, designed with a suitable industrial technology, is capable of producing in routine conditions, on full industrial-scale plant, a very good quality effluent. (COD : 70 mg/l, TSS : 20 mg/l) for pollutant loads in the order of 8 kg COD/m3 day. It enables the fluctuations in the daily flow-rate and pollution load of the influent to be absorbed. The units currently being built are examples of what can be done in compact roofed facilities incorporating a fixed biomass treatment stage, with the objective of reaching a no-nuisance level.

Tests Made of Separate Mechanical Thickening of Surplus Activated Sludge in the Treatment Plant at Wuppertal-Buchenhofen, F.R.G.

For better exploitation of the existing digesters and for optimizing the sludge incinerator, tests have been carried out for mechanical thickening of surplus activated sludge. The biological treatment stage operates at a daily capacity of 6,300 m3 surplus activated sludge with a solids content of 0.7 %. The results of the tests carried out by means of static thickening, flotation, as well as with the aid of nozzle separator, screen bowl, and a standard dewatering centrifuge have not been satisfactory. A newly developed nozzle-thickening centrifuge operating at a rated capacity of 60 m3/h achieved test results within a solids content range of 4 - 6 % in the cake. A larger thickening centrifuge of 120 m3/h capacity is also operating successfully at present. As can be taken from the test results, mechanical thickening of the surplus activated sludge to a solids content of more than 4 % can be achieved, and thus the sludge volume reduced to 1/5 - 1/6 of the original value. By this method, a degree of separation of approx. 80 % and a solids content of between 0.07 and 0.12 % in the centrate is reached without the addition of polymers.

The Use of Biofiltration for Further Wastewater Treatment

The City of Mannheim (FRG) expanded its one stage biological treatment plant by addition of a second stage based on dry bed filtration and designed for an average wastewater flow of QTW = 8.800 m3/h and an average BOD5 of 70 mg/l. Five firms in the foreground of process selection conducted from 1980 to 1982 experiments on purification systems for the effluent from the first biological stage. Systems tested were biofiltration in dry and submerged beds and activated two sludge systems. Filter materials used were inert material, activated carbon and Biolite. In one case a pretreatment by coagulation was employed. The influent of submerged filters without coagulation was supplied with technical oxygen whereas submerged filters with coagulation were supplied with atmospheric oxygen. The two sludge process employed a plastic medium (Flocor E) in an aeration tank of up to 40% total bed volume; aeration was achieved with compressed air. The results of the submerged filtration tests are compared to those of the two sludge system with respect to retention of suspended solids, elimination of BOD5 and COD and soluble and total nitrogenous compounds. A procedural evaluation and cost comparison are made. In addition the problems that arise by solution of oxygen up to high concentrations are indicated and solution possibilities discussed.

Organic groups and molecular weight distribution in tertiary effluents and renovated waters

Group composition and MW distribution of soluble organics in effluents from successive biological and chemical treatment stages were investigated. In secondary effluents, most of the organics fell within the high MW range. Lime treatment caused marked reduction of the latter group, combined with removal of proteins, humics, and carbohydrates. (The overall removal amounted to approx. 65–75%). Simultaneously, there was an increase in the lowest MW range group—strongly hydrophilic, unidentifiable compounds outside the classification scheme used.

Disposal of dairy whey by two stage biological treatment—I kinetic studies of the aerobic stage

A two stage biological treatment process has been proposed for the treatment of whey discharged from cheese and casein factories. The system consists of high rate anaerobic digestion followed by stabilization of the waste in a conventional activated sludge unit. This work embodies the determination of the kinetic parameters describing the second stage—the aerobic biological process. The relationships chosen to describe the system are based on the Monod empirical model describing biological oxidation processes.