The illustrated lighting device is to be placed in a housing lowered into the ground. Influent is directed to a covered anaerobic reactor, and then to an attached growth pretreatment filter that is at least intermittently exposed to atmospheric oxygen. The cross-section shape of the closure of the present invention is generally round. It also includes an annular locator wall that extends upwardly from the second arm. The bias control signal stabilizes the bias voltage of the first amplifier during gain adjustment of the first amplifier. Thus, the ratio of the area of junction between the bottom plate and the electronic cooling element as a whole to the area of the bottom plate of the package can be increased.