Comparing the performance of a High Rate Algal Pond with a Waste Stabilisation Pond in rural South Australia

Author: Alan Neil Buchanan

Buchanan, Alan Neil, 2014 Comparing the performance of a High Rate Algal Pond with a Waste Stabilisation Pond in rural South Australia, Flinders University, School of the Environment

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Abstract

This study compares the performance of two natural wastewater treatment systems; waste stabilisation ponds (WSP) and High Rate Algal Ponds (HRAP) in rural South Australia. The systems were located in similar geographic and climatic zones, East North East of Adelaide. The WSP treated the domestic wastewater from the township of Lyndoch, with an approximate population of 1,750 inhabitants, and daily treatment plant influent of 165 kL. The HRAP treated domestic wastewater from the smaller township of Kingston-on-Murray, with an approximate population of 140 producing daily treatment plant influent of 12 kL. All households in both townships had domestic septic tanks connected to a reticulation system to harvest their overflow to a central sump and pump station that pumped to the treatment plant. The WSP treatment plant was a three cell system with gravity feed between ponds, and a theoretical hydraulic retention time of 36 days in pond 1 and 15 days each in pond 2 and 3, for a total of 66 days. This system was observed over a period of two years. The HRAP was a single raceway 30 m x 5 m with adjustable depth settings. The HRAP was run at 0.32 m, (Θ=4.7 d), 0.42 m (Θ=6.6 d) and 0.55 m (Θ=9.2 d). The depth setting was altered regularly to encompass observation periods in all seasons at all depths. This system was observed for a year. A second period of 9 months of HRAP observations was made in a similar manner, this time using wastewater that had already spent approximately 36 days in a facultative pond. Parameters measured at both sites in all ponds were:- • Continuously logged water temperature, dissolved oxygen and pH • Continuously logged weather data – temperature, wind speed & direction, total solar radiation, UV radiation, rainfall. • Water samples collected at regular intervals from inlets and all ponds and returned to the laboratory for estimations of the following:- o E. coli enumeration o Chlorophyll a o Suspended solids o Turbidity o BOD5 o Nutrients:– NH4-N, NO2-N, NO3-N, PO4-P The results were analysed to compare both the disinfection performance of the two systems and the relative ability to remove nutrients. A comparison was also made of the albazod productivity of the two systems. A mathematical model to predict the E. coli concentration in the HRAP effluent was constructed and the model outputs were compared with eight separate periods of intensive observation of E. coli numbers over periods of two to five days at a time. There was good correlation between model output and E. coli concentration observations. The study answered in the affirmative the question of whether a High Rate Algal Pond system could replace a Waste Stabilisation Pond system in rural South Australia. It also offers clear advice on the design and operation of a High Rate Algal Pond system in rural South Australia.

Keywords: High Rate Algal Pond,Waste Stabilisation Ponds,disinfection,nutrient removal
Subject: Environmental Science thesis

Thesis type: Doctor of Philosophy
Completed: 2014
School: School of the Environment
Supervisor: Prof Howard Fallowfield