Centering of equations in classicthesis style

Question

I'm using the classicthesis package. Unlike math in $$, an equation is not centered:

\begin{equation}
mod(\zeta, G) := \sum_{C \in \zeta} \left ( \frac{\omega(C)}{\omega(E)} - \frac{vol(C)^2}{4 \omega(E)^2} \right )
\label{eq:mod}
\end{equation}

I'd like an equation to be centered with respect to the column by default.

My preamble looks as follows:

%----------------------------------------------------------------------------------------
%   PACKAGES
%----------------------------------------------------------------------------------------

\usepackage{longtable}
\usepackage{minted}
%\usepackage[backend=bibtex]{biblatex}
\usepackage{lmodern}    % standard latex math font
%\usepackage{cmbright}
%\renewcommand\rmdefault{hfoldsty}



\usepackage{todonotes}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[ruled,vlined, linesnumbered]{algorithm2e} % algorithms
\usepackage{scrextend}  % addmargin command comes from here
\usepackage{aurical}
\usepackage{amsthm}
\usepackage{thmtools}
\usepackage{amssymb}
\usepackage{colortbl}
%\usepackage{subcaption}    % TODO: doesn't cooperate with subfig
\usepackage{pgfplots}

% https://tex.stackexchange.com/questions/174186/todonotes-group-list-of-todos-by-section
\usepackage{tocloft,xpatch}




%----------------------------------------------------------------------------------------
% COMMANDS
%----------------------------------------------------------------------------------------

% formatting
\newcommand{\term}[1]{\textit{#1}}
\newcommand{\algo}[1]{\textsf{#1}}
\newcommand{\TODO}[1]{\todo[size=\small, inline]{#1}}

% math
\newcommand{\set}[1]{ \{ #1 \} }

% function definition
\newcommand{\funcdef}[2]
{
    \left\{
        \begin{array}{ll}
            #1 \\
            #2
        \end{array}
    \right.
}


\newcommand{\nwk}{\textsf{NetworKit}\xspace}


%----------------------------------------------------------------------------------------
%  ENVIRONMENTS
%----------------------------------------------------------------------------------------

\newenvironment{koan}
{\color{darkgray} \begin{addmargin}[6cm]{0cm} \begin{footnotesize}}
{\end{footnotesize} \end{addmargin} \bigskip }


%----------------------------------------------------------------------------------------
%  THEOREMS
%------------------------------------------ ----------------------------------------------

\theoremstyle{definition}
\newtheorem{definition}{Definition}

%----------------------------------------------------------------------------------------
%  CONFIG
%----------------------------------------------------------------------------------------

\graphicspath{ {graphics/} }
%\graphicspath{{../Graphics}}

% include needed for pseudocode includes
\input{Pseudocode/Distributed/pseudocodes_setup}

% include needed for TeX-generated plots
\input{graphics/Distributed/plots/plots_setup}

%----------------------------------------------------------------------------------------
%   Colors
%----------------------------------------------------------------------------------------


\definecolor{bg}{rgb}{0.985,0.985,0.985}

\newenvironment{code}[1]
                {
                \begin{minted}[mathescape,
                               linenos,
                               numbersep=5pt,
                               frame=lines,
                               framesep=2mm,
                               fontsize=\footnotesize,
                               bgcolor=codebg]{#1}
                }
                {\end{minted}}

Options to documentclass:

\documentclass[
        twoside,openright,titlepage,numbers=noenddot,headinclude,%1headlines,
                footinclude=true,cleardoublepage=empty,
                BCOR=5mm,paper=a4,fontsize=11pt, % Binding correction, paper type and font size
                ngerman,american, % Languages
                ]{scrreprt}