An initial grab sample from the primary clarifier influent was collected on the 17th May 2009 and analysed for trace metals by an ELEMENT 1 High Resolution Inductively Coupled Plasma Mass Spectrometer in the University of Tasmania Central Science Laboratory, Hobart. The initial metals analysis was undertaken to determine the levels of a broad suite of trace metals for comparison with the estimated trace metal requirements for optimal biological growth reported in the literature (Table 2.1). The concentration of metals in the initial grab sample can be found in Appendix 2. The concentrations of molybdenum and cobalt in the grab sample were an order of magnitude below the estimated trace metal requirements (Table 2.1). The concentration of copper was also below the estimated requirement, with iron and magnesium within the estimated required range for optimal biological growth. Calcium and zinc were detected at significantly higher concentrations than the reported biological requirements (Table 2.1). The measured concentration of zinc (1.35 mg/L) was so high that it would be toxic to AS biota if it remained at this level for extended periods [50, 94]. During the analysis reagent blanks were prepared, however, there were no sample blanks prepared at the time the sample was collected. Therefore, contamination cannot be ruled out as a source of the higher than expected zinc concentration detected in the grab sample.
Primary In COD (mg/L) SE TP C OD R em ov al ( m g/ L) 5000 4000 3000 2000 1000 0 4000 3000 2000 1000 0
27 | P a g e Due to the complex nature of the wastewater the concentrations detected in the grab sample from the Boyer wastewater samples may not be a true representation of the concentration that is bioavailable. Complexation, adsorption and precipitation of metals in activated sludge would decrease the bioavailable portion of some metals especially iron [3]. This will be discussed in full in Chapter 5.
Table 2.1: Experimental results obtained for a range of metals from a Primary Clarifier Influent grab sample collected from the Boyer plant on 17th May 2009. The preliminary analysis of the Boyer sample was determined using ICP MS.
Trace Metals Ca Cu Co Fe Mg Mo Zn
Primary Clarifier
Concentration (mg/L) 11.1 0.08 0.004 1.0 5.9 0.006 1.35
Estimated Trace Element Requirements (mg/L)[8, 71,
76] 3 – 5 0.1 – 1.0 0.02 – 0.50 1 – 4 3 – 10 0.02 – 0.05 0.01 – 1.0
Based on a comparison between their measured concentrations and microbiological requirements calcium, iron, magnesium, copper, zinc, molybdenum and cobalt were selected for further
investigation. Calcium, iron and magnesium were included even though they are within or above the required concentrations in the primary clarifier sample as they are major components for biological cell activity, as indicated by their use as nutrient additions for the standard BOD5 analysis. As the
concentration of zinc was above the maximum estimated requirement for biological growth it was also included in further work.
Two 24 hr composite samples, one from the primary clarifier influent and a secondary clarifier effluent were collected as a quality control measure. The samples were filtered through glass fibre filters and refrigerated by laboratory staff at Norske Skog Boyer on the 17th Nov 2009. The samples were transported to Hobart on the same day, acidified with HNO3 and divided for separate analysis
in Launceston by AAS and Hobart by ICP-MS on the following day (See Table 2.2).
The results from the two inter-laboratory survey samples were comparable (See Table 2.2). From Table 2.2, there were significant changes in the concentrations of metals in the quality control samples compared to the initial grab sample. The quality control samples were collected following the commissioning of the new TMP 3 plant. At the time, operational trials at the plant were using lime as an amendment for pH control as there was no input from the CCS wastewater. Though the
28 | P a g e use of lime was not implemented as a standard procedure, the calcium concentration in the 24 hour composite samples was four times higher than in the initial grab sample of 17th May. The zinc concentration in the quality control samples was 0.22 mg/L and 0.20 mg/L (Table 2.2) in the primary clarifier influent and the secondary clarifier effluent respectively. This was considerably lower than the 1.35 mg/L detected in the initial grab sample (Table 2.1). Due to the variations in the
concentration of zinc detected in the Boyer wastewater and the inability to discount contamination there were no conclusions made in relation to the normal zinc concentration in the SETP.
Table 2.2: Comparative results from selected metal analysis in Launceston and Hobart using AAS and ICP MS, respectively.
Primary Clarifier Influent (mg/L) Secondary Clarifier Effluent (mg/L)
Element AAS CSL - ICP MS
Check Sample AAS
CSL - ICP MS Check Sample Ca 42.18 37.12 47.05 40.42 Co 0.01 < 0.00 0.01 < 0.00 Cu 0.02 0.01 0.02 0.01 Fe 0.37 0.16 0.54 0.24 Mg 8.75 7.21 7.78 6.73 Mo < 0.00 0.01 < 0.00 0.01 Zn 0.22 0.20 0.20 0.19
It was apparent from the inter-laboratory survey samples that the concentration of iron and copper were significantly lower than the initial grab sample at ≤ 0.5 mg/L and ≤ 0.02 mg/L, respectively, justifying their inclusion as metals of interest. There was no apparent change in the concentrations of cobalt, magnesium and molybdenum between the two sampling events.
From the concentrations of metals detected in the initial grab sample and the quality control
samples the selected metals of interest (calcium, magnesium, iron, copper, cobalt, molybdenum and zinc) were retained for further investigation.