Simultaneous Sludge Disintegration and Carbon Source Generation for Enhanced Biological Phosphorous Removal Using Ozonation

摘要

One of the major drawbacks of wastewater treatment is the amount of excess sludge produced,which depends on the type of process applied. Since the quantities of sludge produced in a typicalactivated sludge process are considerable, it has a strong impact on the cost of sludge treatmentand final disposal. The sludge treatment and disposal from an activated sludge process can makeup to 60% of the total wastewater treatment operational cost (Inchauste-Daza et al., 2011). Theozonation of the excess sludge is considered to be one of the extensively studied and successfullyapplied methods for sludge reduction (Chu et al., 2009; Inchauste-Daza et al., 2011). Whensludge is ozonated, a new carbon source is formed and it has been reasoned that due to its newcharacteristics of biodegradability it may be consumed by the microorganisms such as by PAOs(bio-P organisms) in enhanced biological phosphorous removal (EBPR). However, theinvestigation of the use of ozonated sludge as substrate in nutrient removal is limited. Two typesof experiments have been carried out- ozonation tests of activated sludge, and biological activitytests for enhanced biological phosphorous removal. The ozonation of sludge resulted in thereduction of both MLSS and MLVSS; and it is evident from the trend that the volatile fraction isdisintegrated and becomes soluble making the trend of both close to parallel. It has been observedthat while the amount of residual biosolids drops with ozone dose increase, the soluble fractionrises; and the mineralized fraction becomes more significant.The results with acetate (HAc) as carbon source show that during the anaerobic phase all thesubstrate was consumed and stored by PAOs in the first 20 minutes; the poly-P internally storedwas effectively used as energy, releasing up to 3.30 mg PO_4-P/g VSS at the end of the anaerobicphase. In the following stage, PAOs did not uptake all the phosphorus, and thus the specific Puptake was found to be 3.19 mg PO_4-P/g VSS at the end of the tests. The results fromdisintegrated sludge use indicate that the ozonated sludge at various ozone doses were certainlyused by PAOs during the anaerobic phase. However, not all substrates were identically used. Thehighest specific P-release was found to be 2.78 mg PO_4-P/g VSS, with a rate of 5.52 mg PO_4-P/gVSS·h, when using ozonated sludge at higher dose of 0.13 g O_3/g MLSS as substrate. The resultsindicate that the properties of the carbon source present in the ozonated sludge are promising; thewastewater treatment plants can be integrated with sludge ozonation to significantly reduce theamount of sludge generation and external chemical (carbon source) requirement.