# Quantifying Total Phosphorus and Heavy Metals in Residential Septage
## 3 Results and Discussion
### Mass and Watershed Mass of Pollutants from Domestic Septage
The studied septic tanks exhibited large variability in layer thickness and concentration, mass, and total mass of pollutants (Figures 2-4 and Tables 2 and 5). There may be several reasons for the variability in the data collected by the current study, which include but are \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Pollutant**} & \multicolumn{2}{c}{**Median (Range)**} & \multicolumn{2}{c}{**Mean (SD)**} \\ \cline{2-6}  & **Weighted** & **Watershed a** & **Weighted** & **Watershed a** \\  & **Mass (g)** & **Mass (g)** & **Mass (g)** & **Mass (g)** \\ \hline \multirow{2}{*}{TP} & 19.5 & 1694 & 66.6 & 5792 \\  & (0.9–1041) & (76.3–90587) & (178) & (15,483) \\ \multirow{2}{*}{Cadmium} & \multirow{2}{*}{(\(<\)0.01–2.0)} & \multirow{2}{*}{(\(<\)0.9–173)} & \multirow{2}{*}{(0.5)} & \multirow{2}{*}{(45.7)} \\  & (\(<\)0.01–2.0) & & & & \\  & 1.3 & 117 & 19.3 & 1681 \\ \multirow{2}{*}{Copper} & \multirow{2}{*}{(0.1–520)} & \multirow{2}{*}{(4.7–45,238)} & \multirow{2}{*}{(86.9)} & \multirow{2}{*}{(7562)} \\ Lead & & 1.8 & 152 & 4.8 & 419 \\  & (\(<\)0.01–44.2) & & & & (10.8) & (937) \\ Nickel & & 1.3 & 112 & 1.5 & 129 \\ \multirow{2}{*}{Zinc} & \multirow{2}{*}{(\(<\)0.01–4.3)} & \multirow{2}{*}{(\(<\)0.9–378)} & \multirow{2}{*}{(1.4)} & \multirow{2}{*}{(121)} \\  & & 13.8 & 1202 & 55.6 & 4838 \\ \multirow{2}{*}{Zinc} & \multirow{2}{*}{(0.3–788)} & \multirow{2}{*}{(26.8–68,514)} & \multirow{2}{*}{(136)} & \multirow{2}{*}{(11,865)} \\ \hline \hline \end{tabular}  
* These estimates were based on the studied sub-watershed that drains to Lick Creek and not the entire Lick Creek Watershed.  
\end{table} 
Table 4: Estimated mass in all septic systems in the studied sub-watershed (\(n=87\)) based on the median and mean concentrations of total phosphorus (TP) and trace metals from the studied septic tanks (\(n=37\)). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Tank**} & \multirow{2}{*}{**Layer**} & \multicolumn{2}{c}{**Layer**} & \multicolumn{4}{c}{**Pollutant Concentration (mg L\({}^{-1}\))**} \\ \cline{3-8}  & & **(\%)** & **TP** & **Cadmium** & **Copper** & **Lead** & **Nickel** & **Zinc** \\ \hline
1 & Scum & 0\% & & & & & \\
2 & Scum & 19\% & 835 & 0.8 & 206 & 24.5 & 2.1 & 358 \\
3 & Scum & 4\% & 54.4 & 0 & 9 & 0 & 0 & 1.4 \\
4 & Scum & 0\% & & & & & & \\
1 & Liquid & 84\% & 8.5 & 0.2 & 4.5 & 3.3 & 0.1 & 60 \\
2 & Liquid & 38\% & 21.6 & 0.3 & 4.1 & 4.3 & 0.3 & 76.8 \\
3 & Liquid & 72\% & 8.2 & 0 & 4.8 & 0 & 0 & 0.8 \\
4 & Liquid & 72\% & 9.8 & 0 & 1.6 & 0 & 0.2 & 3.8 \\
1 & Sludge & 16\% & 199 & 0.6 & 112 & 9 & 4 & 192 \\
2 & Sludge & 44\% & 252 & 0.6 & 222 & 12.5 & 1.1 & 256 \\
3 & Sludge & 24\% & 3.2 & 0 & 8.2 & 0 & 0 & 1.1 \\
4 & Sludge & 28\% & 45.7 & 0 & 2.8 & 0.3 & 0.1 & 2.8 \\ \hline \multirow{4}{*}{Median (Range)} & \multirow{2}{*}{Scum} & 2\% & 444 & 0.4 & 108 & 12.3 & 1.1 & 180 \\  & & (0–19\%) & (54.4–835) & (\(<\)0.01–0.8) & (9–206) & 24.5) & (\(<\)0.01–2.1) & (1.4–358) \\ \multirow{2}{*}{Median (Range)} & \multirow{2}{*}{Liquid (38–84\%)} & \multirow{2}{*}{(8.2–21.6)} & \multirow{2}{*}{(\(<\)0.01–0.3)} & \multirow{2}{*}{(1.6–4.8)} & \multirow{2}{*}{(\(<\)0.01–4.3)} & \multirow{2}{*}{(\(<\)0.01–0.3)} & \multirow{2}{*}{(0.8–76.8)} \\  & & 26\% & 122 & 0.3 & 60.1 & 4.7 & 0.6 & 97.4 \\  & & (16–44\%) & (3.2–252) & (\(<\)0.01–0.6) & (2.8–222) & (\(<\)0.01–4.0) & (1.1–256) \\ \hline \multirow{4}{*}{Mean (SD)} & \multirow{2}{*}{Scum} & 6\% & 444 & 0.4 & 108 & 12.3 & 1.1 & 180 \\  & & (9\%) & (552) & (0.6) & (139) & (17.3) & (1.5) & (252) \\ \multirow{2}{*}{Mean (SD)} & \multirow{2}{*}{Liquid (20\%)} & 66\% & 12.0 & 0.1 & 3.8 & 1.9 & 0.2 & 35.4 \\  & & (20\%) & (6.4) & (0.2) & (1.5) & (2.2) & (0.1) & (38.8) \\ \multirow{2}{*}{} & \multirow{2}{*}{Sludge} & 28\% & 125 & 0.3 & 86.3 & 5.5 & 1.3 & 113 \\  & & (12\%) & (119) & (0.3) & (104) & (6.3) & (1.9) & (131) \\ \hline \hline \end{tabular}
\end{table}