| dc.description.abstract | Industrial wastewater effluents discharged that contains high nitrate concentration can cause eutrophication, poisoned to baby and child, and also toxic to water biota. High nitrate concentration in drinking water can cause Methemoglobinemia (blue babies). Nitrate-nitrogen yielded from ammonium- nitrogen oxidation through aerobic pond on WWTP.
The case study at WWTP of PT. Capsugel Indonesia (PTC) was aimed to optimalize denitrification process in order to achieve the nitrate effluent quality as according to Baku Mutu I. This research was initiated by identification of WWTP process, analysing process influencing denitrification and followed by various process such as: an internal recycle treatment, SRT and HRT treatment at clarifier, jar test and determination of methanol dosing (as additional substrat) that influenced denitrification. All analytical procedures followed a Standard Operation Procedure (SOP) from WWTP PTC and based on HACH manual book and APHA 1992.
Modified Ludzak-Ettinger (MLE) is a model which is most commonly used at WWTP because of its simply process. MLE represent nitrification- denitrification system in a single sludge activated-sludge for nitrogen removal which combine carbon removal, amonia oxidation and nitrate reductation in the same process.
Shock loading and fluctuation of ammonium-nitrogen in the influent
reduced WWTP performance. Initially, nitrate concentration level has been
controled by adjusting the rate of mixed liquor recicling. Mixed liquor from
aerobic pond to anoxic pond wes expected can bring nitrate as much as possible
for oxidizing carbon source where nitrates replace oxygen in denitrification.
Increasing of the mixed liquor recirculation rate really did not bring nitrate
degradation level to the effluent. This happened because all COD as carbon source
in anoxic pond have been used so that anoxic pond reached the maximum capacity
for denitrification. Another possibility is that WWTP depend on carbon source
only from waste influent. Carbon source from influent pertained a slowly
biodegradable COD so denitrification rate also became slow. One of MLE system purpose is to reduce the cost of additional carbon sources, but in this case, the system was actually require external carbon sources. This research used technical methanol 2% (v/v) with dosing rate was 4 L/h combined with internal return rate (IR) = 4Q, the return activated sludge (RAS) rate IQ and influen rates (Q) = 1.2 m³/h gave acceptable results for nitrate-nitrogen removal. This combination reduced the average effluent nitrate concentration from 46.07 mg/L NO3-N to 12.6 mg/L NO3-N. This value below the regulation of Baku Mutu 1. The methanol addition in WWTP increased alkalinity formed during denitrification. It reduced up to 80% of Na2CO3 consumption. | id |
