Effect of Activated Carbon on Biological Treatment of Specific Pollutants and Wastewaters: Laboratory- and Pilot-Scale Studies - Activated Carbon for Water and Wastewater Treatment - page 112

Table 4.7 Improvement of effluent quality in leachate treatment by PAC addition to batch
reactors [96].

Leachate ratio in the total
wastewater (%)

Reactor
configuration

PAC dosage
(mg L -1 )

Initial SCOD
(mg L -1 )

Final SCOD after
72 h/( mg L -1 )

5 AS 0 670 95

5 AS+PAC 2500 598 29

10 AS 0 1492 200

10 AS+PAC 2500 1467 68

15 AS 0 1575 280

15 AS+PAC 2500 1538 99

20 AS 0 2466 548

20 AS+PAC 2500 2556 112

25 AS 0 3135 399

25 AS+PAC 2500 3128 109

AS: activated sludge reactor
AS þ PAC: activated sludge reactor with powdered activated carbon (PAC) addition

sanitary landfill had the following characteristics: pH: 8.2, Total COD (TCOD):
10750mg L 1 , Soluble COD (SCOD): 9070mg L 1 , BOD 5 : 6380mg L 1 , TKN:
2031mg L 1 ,NH 4 2 N : 2002mg L 1 ,NO x -N: 128mg L 1 , Total P: 6.8mg L 1 ,
Alkalinity: 10 600mg CaCO 3 L 1 . Leachate and domestic wastewater were mixed
such that the volumetric ratio of leachate in the total wastewater varied from 5%
to 20%.
Biological treatability of the leachate was first studied in batch activated sludge
reactors. Activated sludge (AS) reactors received a feed composed of leachate
and domestic wastewater. The abbreviation AS+PAC indicates activated sludge
reactors which also contained PAC at a concentration ranging from 100 to
3500mg L 1 . The performances of both systems were compared with each other.
Batch studies showed that the leachate contained a nonbiodegradable COD frac-
tion of about 30%. Thus, the nonbiodegradable COD was as high as 3225mg L 1 .
The effect of PAC addition was not significant in the initial periods of aeration
where biodegradable matter was mainly removed. The main effect of PAC was
observed in later periods when PAC adsorbed nonbiodegradable matter and
considerably lowered the final residual COD (Table 4.7). Moreover, PAC addition
considerably improved nitrification and accelerated NO x -N production because
of adsorption of toxic/inhibitory compounds. However, in all cases, high nitrite
accumulation was observed in the reactors, indicating that the activity of nitrite-
oxidizing bacteria was still inhibited.
Experiments were also conducted in Semi-Continuously Fed Batch (SCFB) and
Continuous-Flow (CF) activated sludges with recycling. SCFB operation involved
daily feeding and wastage of wastewater in batch reactors. In both types of
operations, the positive effect of PAC on organic carbon removal and nitrification
became more apparent at high leachate inputs. Organic carbon removal and
nitrification were significantly enhanced by PAC addition in SCFB operation, as