Which one of the following is correct?
- The partially treated effluent from a food processing industry, containing high concentration of biodegradable organics, is being discharged into a flowing river at a point $\text{P}$. If the rate of degradation of the organics is higher than the rate of aeration, then dissolved oxygen of the river water will be lowest at point $\text{P}$.
- The most important type of species involved in the degradation of organic matter in the case of activated sludge process based wastewater treatment is $\textit{chemoheterotrophs}$
- For an effluent sample of a sewage treatment plant, the ratio $\text{BOD}$ $_{5-\text{day},20^{\circ}C}$ upon ultimate $\text{BOD}$ is more than $1$
- A young lake characterized by low nutrient content and low plant productivity is called $\textit{eutrophic lake}$