analysis of a pilot-scale anaerobic baffled reactor treating domestic ...

5 EXPERIMENTAL PHASES II-IV: KINGSBURGH WWTP 2002-2004
The pilot-scale ABR was moved to Kingsburgh WWTP in January 2002. Operation at Kingsburgh
WWTP formed the basis of an MScEng Thesis (Mtembu, 2005). Kingsburgh WWTP is situated
approximately 30 km south of Durban and 30 minutes drive from UKZN. This works treats a
wastewater that has no formal industrial effluent component. It serves a community of about 350 000
population equivalents from middle-income suburbs. The pilot-scale ABR was moved from Umbilo
WWTP to Kingsburgh as it was believed that a better understanding of the functioning of the ABR in
sanitation would be obtained without complications from trade effluent.
A disadvantage of Kingsburgh WWTP compared to Umbilo WWTP was that there was no analytical
laboratory on site. Plant workers could be persuaded to record flow rate data and to report if the
reactor did not seem to be working, but were otherwise not involved in the operation of the plant.
Composite samples of inflow wastewater were withdrawn from the head of works by WWTP staff,
and the results of routine analyses on these samples were made available to the project team by the
municipality. Sampling was performed by project team members and samples had to be transported
back to the university laboratory or to the central municipal laboratories by project team members with
some unavoidable sample deterioration. While improved control and documentation of plant operation
was achieved at Kingsburgh WWTP, there was an inevitable decrease in the abundance and (in some
analytes), quality of data that were obtained during this time.
5.1 KINGSBURGH WWTP INSTALLATION
Prior to removal from Umbilo WWTP, the ABR was allowed to stand for a week to allow sludge to
settle. The liquid fraction in each compartment above the bottom sample/drain valve was drained
away, leaving 200 mm of sludge in the bottom of each compartment. This sludge was available as
seed sludge for start-up at Kingsburgh WWTP.
The pilot-scale ABR was installed near the head of works at Kingsburgh WWTP. The feed pump was
lowered into a sump (Figure 5.1 (right)) that sent screened and degritted wastewater to the activated
sludge plant. Incidences of rags blocking the pump were substantially less during operation at
Kingsburgh WWTP compared to those experienced at Umbilo WWTP since the Kingsburgh
wastewater contained no textile industry effluent. However, string, rubber and hair regularly found
their way into the pump, causing interruptions to pumping and damage to the pump motor. Several
means of eliminating these from the pump were attempted, but by far the most successful measure was
installing the pump in a laundry basket (Figure 5.1). Instances of pump blockages were reduced by
more than half as a result of the laundry basket system (Mtembu, 2005). During the time the ABR was
operated at Kingsburgh, at least 5 laundry baskets were used in this way!
In the first year of operation at Kingsburgh WWTP (Phase II), there were a number of occasions when
the outlet pipe from the ABR blocked. Under normal operation, a siphon breaker on the outflow line
controlled the height of liquid in the reactor. However, when the outlet pipe became blocked, the
reactor would fill up to as much as 100 mm above the normal operating level, causing the
accumulation of up to 300 ℓ of excess liquid in the reactor.
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