TITLE:
Process Adaption of a Small WWTP Operated at Low Loading Conditions for Substantial Energy Savings
AUTHORS:
Stig Morling Sweco, Roland Johansson Pireva
KEYWORDS:
Activated Sludge, Low Load, Energy Savings, Phosphorus Removal, Inter-mittent Operation
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.12 No.6,
June
5,
2020
ABSTRACT: The very long tradition
of the activated sludge treatment model within the water industry has
demonstrated very versatile possibilities to adopt the operation mode for
different enhancements. By looking into other treatment models within the
activated sludge family it is possible to find alternatives for the operation.
This paper concentrates on the possibilities to improve even small WWTP with
respect to energy savings. The small plant in Northern Sweden, called Rosvik
WWTP, is given as an example. Some important findings related to the
intermittent aeration mode may be summarized as follows: 1) An energy savings
for the operation of the small WWTP with respect to aeration needs that
resulted in a decrease of the energy power supply by more than 35%, as compared
with the previous operation based on continuous aeration; 2) The up to date
effluent levels with respect to the main pollutants have remained at very good
levels in 2020, P-level averages 0.16 mg P/l versus consent level 0.5 mg P/l; COD-level 40 versus 70 mg/l and BOD7 9 versus 15 mg/l; 3) Sometimes, also improved sludge settling characteristics
have been observed, thus providing improved discharge figures; 4) The potential
to develop an enhanced biological phosphorus removal. There are however some needed conditions to accomplish these
improvements: 1) Reliable on-line probes for both oxygen control,
SS-concentration control and optionally also for nitrogen control; 2) A
flexible automation system that allows the needed process modifications to take
place; 3) And finally, very important dedicated and competent plant operators,
with the needed curiosity for operation improvements.