Matlab code to generate Figure 4

% calculate staedy state CSTR volume for different substrate, product and
% flow
clear all

flow = [1:50]';
S = [0.5:0.01:0.9];% in effluent water

for i=1:length(flow)
    for j=1:length(S)
        P(j) = 5.2848-S(j);% assumning 100 mg/l ammonia were in the feed water of reactor1
        V(i,j)=steadystate_cstr_volumeR2(flow(i),S(j),P(j));
    end
end

figure
surf(P,flow,V)
title('Volume of reactor 2 in steady state in [L]', 'FontSize',14)
xlabel('nitrous oxide concentration in [mmol/L]','FontSize',14)
ylabel('flow in [L/min]','FontSize',14)
zlabel('volume of reactor in [L]')
colorbar