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Narjes Shahheidar, Sahand Jorfi, Afshin Takdastan, Neemat Jaafarzadeh and Mehdi Ahmadi

Abstract

Sludge conditioning is an important stage in sludge management. In the present study, a sequence of freeze/thaw-electro-Fenton process was designed and specific resistance filtration (SRF) was monitored during sludge conditioning as an important factor in sludge dewaterability. Furthermore, protein and polysaccharide concentrations were measured during the experiments. Results showed that the lowest SRF value contributed to −10°C in freezing process which showed a reducing trend by decreasing solution pH. In addition, results revealed that solution pH less than 3 caused a significant improvement in sludge dewatering; so the lowest SRF has been registered at pH = 2. By increasing current intensity from 0.5 to 1A, SRF values were reduced and then followed by an enhancement with increasing current intensity to 3.2 A. The lowest SRF value (6.1 × 104 m/kg) was obtained at H2O2 = 30 mg/L which was the best conditions for sludge dewatering.

Open access

Mehdi Hajsardar, Seyed Mehdi Borghei, Amir Hessam Hassani and Afshin Takdastan

Abstract

Optimized methods for simultaneous removal of nitrate, nitrite and ammonium are important features of nutrient removal. Nitrogen removal efficiency in an intermittently aerated sequencing batch reactor (IA-SBR) with multiple filling events was studied. No external carbon source was added and three filling events were considered. Oxidationreduction potential (ORP) and pH curve at solids retention time (SRT) of 20 d were analyzed. Effects of three organic loading rates (OLR), 0.67, 1.0 and 1.5 kgCOD/m3d, and three nitrogen loading rates (NLR), 0.054, 0.1 and 0.15 kgN/m3d, on nitrogen removal were studied. Nitrate Apex in pH curve and Nitrate Knee in ORP profile indicated that the end of denitrification would be achieved sooner. The kinetic coefficients of endogenous decay (kd) and yield (Y) were identified to evaluate heterotrophic specific denitrification rate (SDNRb). In period 2 at NLR of 0.054 kgN/m3d and considering 2 anoxic and 3 aerobic phases, nitrogen removal efficiency was 91.43%.