Treatment of a recycled paper mill waste water using an Upflow Anaerobic Sludge Blanket (UASB) Reactor

Abstract

Manufacturing of paper by recycling of waste paper is currently receiving attention allover the world especially in the developing countries as a consequence of the high cost associated with production of paper from wood and the global environmental campaign against deforestation. As paper manufacturing from waste paper involves many steps of process, it results in effluents whose characteristics vary considerably. Application of Anaerobic treatment systems in the developing countries especially tropical countries (e.g. sub-saharan) can highly be feasible because the system could be operated successfully at ambient temperature and hence the cost for heating the system will be omitted. Moreover, the methane gas produced by such systems can contribute considerably to solving the problems associated with energy availability in these countries. In this study, the characteristics of a recycled paper mill (Chandaria paper mill, Nairobi, Kenya) waste water was investigated and the feasibility of its treatment anaerobically was studied in a laboratory scale UASB rector. The waste water was found to be highly biodegradable with a COD concentration ranging between 1900 and 2300 mg/1 and a BOD cencentration ranging between 1100 and 1300 mg/1. The COD/BOD cerrelation being expressed by:- BOD5 = 0.59 COD + 2.24 The tetal suspended selids cencentration was in the range of 500-900 mg/l. The waste water was acidic (PH between 3 and 5) and deficient in basic inerganic nutrients (phosphereus 3-5 mg/l and NH3-N 0.0). Appreximately all the tetal kjeldahl nitrogen (TKN) exist in the waste water was asseciated with erganic matter at a concentratien ef 11-26 mg/l. The sulphate centent was between 87 and 164 mg/l. The final industrial effluent flow rate was ranging between 1700 and 2100 m3/d and the waste water temperature level was at 22-28°C. The treatability study shewed that, it is feasible to. treat this waste water in a UASB system seeded with sludge frem a municipal anaerebic digester at ambient temperature (average 22°C) whereby the efficiency ef the erganic content remeval in terms ef seluble COD was 58-~3% at an optimum erganic leading rate between l2-l5Kg COD/m3/d. This corresponded to. a hydraulic retentien time (HRT) of 3 hours at an influent COD cencentratien ef 2100 mg/l. The average total biegas preduction was equivalent tro 0.2 litre/g COD remeved. Measurement ef different was~e water parameters; COD, shert chain fatty acids (prepienic and acetic acids), sulphate, pH, free and saline ammonia, organic nitrogen, and total suspended solids; along the rector length provided interesting information regarding the system behavior. The results conform with results obtained elsewhere.