Analysis of a mechanical mixer performance in anoxic reactor

Denitrification is a key process in wastewater treatment since it is responsible for the effective nutrient removal. It requires anoxic conditions, where only chemically bound nitrogen is used as an oxygen source, and no aeration is applied. In suspended biomass systems the growth and homogenization of biomass is essential, high degree of mixing is required, which is achieved only by using mechanical mixers. Mechanical mixing performance relies on the mixing power determined by the equipment dimensions and rotational speed. In this paper the effect of three different rotational speed (rpm: 100, 400, 900 min-1) on flow field and mixing conditions are evaluated. As a result of the simulations, the acceptable flow field was achieved at 400 rpm. The outcome of this research is that the high degree of energy transfer from mixers to fluid flow deteriorated mixing efficiency

Fine-Tuning the Aeration Control for Energy-Efficient Operation in a Small Sewage Treatment Plant by Applying Biokinetic Modeling

Wastewater treatment is an energy-intensive process for treating liquid-phase pollutants in urban settlements. The aerobic processes of the biological treatment involve a significant air demand. An optimal control strategy could be used to minimize the amount of excess air entering the system due to safety factors applied in the design procedures. A plant-wide mechanistic modeling approach including an activated sludge model and one-dimensional settler model was proposed as an effective tool for predicting the actual air demand and for selecting the optimal aeration strategy. In this study, a sewage treatment plant receiving strong influent flow was investigated. At the sludge ages of 14–18 days, the plant was capable of achieving a 90% organic matter reduction and 85% nutrient reduction. By applying a constant dissolved oxygen concentration of 1.5 mg/L, the air demand decreased by 25%, which could be further increased by 10% if the cascade ammonium control approach was applied at peak periods. The dependence of the aeration energy demand on the temperature and dissolved oxygen was formulated, meaning the operators could select the optimal setpoint and minimize the energy consumption while the effluent quality requirements were met

Decentralizált szennyvíztisztítás szerepe a települési vízgazdálkodásban = Role of the Decentralized Wastewater Treatment in Municipal Water Management

A különböző szennyvízkibocsátások elvezetése, kezelése kiemelt fontosságú a közegészségügyi kockázatok elkerülése és a befogadó vízminőségének megóvása érdekében. A csatornahálózat kiépítésekor arra törekszünk, hogy a szennyvíz szállítását úgy végezzük, hogy abban biológiai folyamatok, iszaplerakódás ne induljon be. Az urbanizáció hatására a meglévő hálózatok túlterheltté válhatnak, a telepre a szennyvíz hosszabb úton érkezhet meg. A kiszolgált agglomeráció bővülése esetén szóba jöhetnek decentralizált szennyvízkezelő megoldások, melyek lehetnek a szennyvíz keletkezési helyénél létesített több kisebb kapacitású telep, kisebb lakóövezet, egy-két családot kiszolgáló egyedi kisberendezés és/vagy természetközeli (extenzív) szennyvíztisztítási rendszerek. A cikk célja ezen lehetőségek feltárása

Genome-level insights into the operation of an on-site biological wastewater treatment unit reveal the importance of storage time

On-site wastewater treatment systems are gaining popularity in areas where centralized wastewater treatment is not available. In the current case study a domestic activated sludge system was investigated, where treated effluent was stored in a short-term (1 week turn-over time) and a long-term (over 2–3 months) storage tank and was then used for irrigation. This design provided a unique opportunity to assess the chemical and microbial changes of the effluent upon storage. Long-term storage greatly improved both the chemical quality and the degradation efficiency of most organic micropollutants examined, including petroleum hydrocarbons and the pesticide diethyltoluamide. Taxonomic profile of the core microbiome of the effluent was also influenced upon storage. Relative abundance values of the members of Azoarcus and Thauera genera, which are important in degrading polycyclic aromatic hydrocarbons compounds, clearly indicated the biodegrading activity of these microbes across samples. The abundance of xenobiotics degradation functions correlated with the observed organic micropollutant degradation values indicating efficient microbial decomposition of these contaminants. Functions related to infectious diseases also had the highest abundance in the short-term storage tank corresponding well with the relative abundance of indicator organisms and implying to the significance of storage time in the elimination of pathogens. Based on these results, small, on-site wastewater treatment systems could benefit from long-term storage of wastewater effluent