Biological nitrification and denitrification of opto-electronic industrial wastewater.
Development and application of biological nutrient removal processes accelerated significantly over the past decade due to more stringent nutrients (nitrogen and phosphorus) discharge limits being imposed on wastewater treatment plants. The opto-electronic industry has developed very fast over the past decade in the world. The wastewater often contains a significant quantity of organic nitrogen compounds and has a ratio of over 95% in organic nitrogen (Org-N) to total nitrogen (T-N). In this study, a 2-stage Anoxic/Aerobic pre-denitrification process was established and the efficiency of wastewater treatment was evaluated. Wastewater from an actual LCD-plant was obtained as the sample for looking into the feasibility of opto-electronic industrial wastewater treatment. Hydraulic retention time (HRT) and mixed liquor recycle rate (MLR) were controlled independently to distinguish between the effects of these two factors. Under suitable HRT and mixed liquor recycle ratio, effluents of NH4-N, NOx-N and COD can fall below 20 mg/l, 30 mg/l and 80 mg/l.
Effect of feed composition, aerobic volume fraction and recycle rate on nitrogen removal in the single-sludge system
Abstract A recently developed and experimentally validated model was used to delineate the effects of various design and operation parameters on the performance of single-sludge systems. Model simulation resulted in charts which illustrate the mutual effects of raw feed COD/ammonia ratio, aerobic volume fraction and recycle rate. The most significant phenomenon, observed experimentally and supported by the simulation, is that increasing recycle may lead to increased effluent nitrate. This situation may occur under low raw COD/ammonia ratios, whereas for high COD/ammonia ratios, as in most domestic wastes, an opposite phenomenon occurs. This means that the recycle has an optimum value which depends on feed composition and on aerobic/anoxic fractionation of the system. The presence of viable cells in the feed in significant numbers affects the composition of biomass in the system and the removal of nitrogen compounds.
Biologische Denitrifikation nitrathaltiger Abwässer und Grundwässer
Biological denitrification of nitrate-containing waste water and ground water. The differing objectives serve to distinguish processes for the treatment of waste water and those for the production of drinking water. In waste water purification, frequent use is made of submerged reactors with deposition and recycling of bacteria. The carbon compounds required by the bacteria are either present in the water or have to be added. If the nitrogen is present as ammonium in the waste water, then there are several different ways of combining nitrification and denitrification reactors. In production of drinking water, both heterotrophic and autotrophic bacteria are used. Since the bacteria are not allowed to enter the supply network, fixed reactors or other reactors with immobilised biomass are used. Sand bed filters are still necessary to retain compounds from the water after denitrification.