Effect of EDTA on activated sludge properties

Bacterial extracellular polymers have been found to be important in bioflocculation of activated sludge. In this study ethylene diamine tetra acetic acid (EDTA) method of extracting bacterial extracellular polymers is examined. Following extractions, it is observed that EDTA extracted significant amounts of biopolymers. However, the chemical treatment causes serious changes in sludge properties. Sludge particle size is reduced from 21 mum to 14.6 mum, filtration properties of sludge deteriorates, indicated by an increase of capillary suction time (CST) from 48.1 sec to 232 sec and the viscosity of sludge increases from 5.5 cP to 7.1 cP. The effects are so dramatic, that it is concluded that beyond extracting biopolymers, this technique damages the microbial cell walls and solubilizes some cells

Effect of solution physical chemistry on the rheological properties of activated sludge

Knowledge on rheological properties of sludge is important for the design of pumping and transport facilities and as a tool in process control during treatment. Concentrated activated sludge is known to behave as a non-Newtonian material. The contribution to non-Newtonian behaviour is believed to originate from the colloidal properties of solids more than from the molecular properties of the suspension. Considering that the colloidal proper-ties of sludge depend on factors like pH, conductivity. solids concentration and flocculation properties. this study examines the effects of these variables on the theology of activated sludge. Results show that the rheograms obtained fa best to a power law model indicating that the flow of activated sludge can best be expressed by the pseudoplastic flow model. It is also observed that the apparent viscosity increases sharply with the increase of solids concentration. From the pH values studied, the one that causes the lowest viscosity is the pH 5.5. As the pH increases, the viscosity measured increases considerably. This makes sense considering that the isoelectric point of bacteria is at pH 2-4. Conductivity is also found to affect the viscosity greatly; such that a the conductivity increases, the apparent viscosity decreases. Finally, experimental results reveal that the presence of extracellular polymers and the flocculated nature of activated sludge affect its viscosity

Çamur Stabilizasyon Süreçlerinin Çamurun Mikrobiyal Kalitesine Etkisi

Anaerobik çürütme işlemi uzun yıllardır çamurdaki patojen bakterilerin büyük oranda giderilmesini sağlayan bir çamur stabilizasyon tekniği olarak bilinmekte ve bu yönüyle çürütme sonrası elde edilen arıtım çamurları tarımsal amaçla kullanılmaktadır. Ancak yakın tarihlerde arıtma tesislerinde anaerobik çürütme işleminin ardından uygulanan susuzlaştırma aşamasından hemen sonra ve takip eden depolama süreci boyunca çamurdaki indikatör bakteri düzeylerinde ani artışlar gerçekleştiği anlaşılmıştır. Bu artışların kültür metodlarına dayalı bakteri sayım teknikleri, santrifüj sırasında parçalama kuvvetlerine maruziyet, kontaminasyon ve çürütme sürecinde toksik veya bakterileri inhibe edici bazı kimyasalların ortaya çıkması gibi çeşitli faktörlerin etkisiyle gerçekleştiği düşünülmekle beraber bu duruma sebep olan asıl mekanizma(lar) hala tam olarak anlaşılamamştır. Proje teklifinin amacı ülkemizdeki arıtım süreçlerini bu durumu göz önüne alarak değerlendirmek ve olası artışların sebeplerini araştırmaktır. Çalışma kapsamında, Ankara Arıtma Tesisi başta olmak üzere çeşitli arıtma tesislerinden, susuzlaştırma işlemi öncesi ve sonrasında alınan çamur örneklerinin hem standart kültür metodlarıyla hem de moleküler bir yöntem olan Real Time-PCR ile analiz edilmesiyle indikatör bakteri seviyeleri arasındaki farkların belirlenmesi ve bu durumu açıklayan mekanizmaların değerlendirilmesi amaçlanmaktadır

Occurrence and Reduction of Emerging Contaminants in Sludge

Emerging contaminants consist of a wide range of anthropogenic as well as natural substances which include pharmaceuticals,personal care products, steroid hormones, industrial chemicals, pesticides and many other emerging compounds. Since theirconcentrations vary from a few ng/L to several μg/L, they may also be called as micropollutants. There has been a growingawareness and concern about these chemicals for the last few decades since many of these are known to have toxic, carcinogenic orendocrine disrupting properties.Limited removal of most of these compounds during wastewater treatment processes, cause them enter the water resources andmove up the food chain. The hydrophobic nature of many of these compounds promote their accumulation in organic phases includingsludge during wastewater treatment plants. This creates extra concern due to the beneficial use of sewage sludge in soil in manycountries around the World. The chemically complex nature of many micropollutants make them hard to degrade during conventionalwastewater and sludge treatment systems. Besides, the presence of wide variety of chemicals indicate that one single treatment type(aerobic or anaerobic) may not be enough to effectively remove them from wastewater and sludge.The way wastewater treatment plants and sludge treatment units operated act as an important determinant on the final concentrationof these chemicals. This talk will highlight the occurrence of emerging contaminants in wastewater and sludge and the governingfactors to reduce them from wastewater effluents and from sludge