10 Commandments for By STUART WARD, General Manager of Process Engineered Water Equipment a ater treatment pro-fessionals, whether f they are operators, t vendor representa-v tives or managers, are t often tasked with the removal of total sus-pended solids (TSS) from a waste-stream. This removal may be necessary in order to meet regulatory permit requirements or simply as cost avoidance. Universally the goal is to remove as many solids as pos-sible at the lowest cost. The following rules may be utilized in a wide variety of industrial wastewater applications. And I admit to a bias toward dissolved air flotation (DAF) over a tra-ditional clarifier for solids removal. Why? Because a DAF is easier and quicker to trouble-shoot and it is often the nature of solids that they can be made to read-ily float. To a degree, these rules may be applied to the municipal field. However, the focus within is industrial applications as that is where my expertise is. Industrial wastewater comes in many forms from the simple to the complex; by boiling TSS down to these 10 commandments, better treatment results can be achieved. These basic principals were learned through many years of personal experience first as a “water-treater,” selling coagulants 20 Pollution Engineering SEPTEMBER 2012 Effective TSS Treatment Removing solids from wastewater is not always a simple matter of ﬁ ltering the water. The suggestions below will save a lot of time and money if followed. W and flocculants and later as a wastewater systems solution engineer. During a stint peddling chemistry, I often found wastewa-ter treatment systems either missing critical pieces of equipment or equipment that was not up to the job at hand. The latter may have been due to poor quality out-dated equipment, or simply equipment being misapplied. Unfortunately, it was often operator neglect or even incompetence. A key point about these rules is that they are cumulative. That is, the rules stack effi-ciency in layers and each layer brings with it increased opportunity for cleaner water. Above is a DAF designed and built by P.E.W.E. Provideth adequate flow and load equalization There are two major reasons for adequately controlling the flow and load coming out of a plant. The flow needs to be controlled so that all downstream equipment can be sized such that it consistently operates within an optimal range. In order to do so, an equalization tank (EQ) or basin must be used. This tank will balance a varying discharge flow rate. The tank should be sized at a proportion to the daily plant flow. The more the flow rate varies, the larger the percentage of the daily flow the tank should be designed to handle. As a general rule of thumb, start with 25 percent. If there are wide swings, such as a high flow during nightly clean-up, the percentage might creep to 50 percent. Keep in mind, EQ sizing depends upon other factors to be taken into account, including available space, odor concerns, contain-ment requirements and budget. The second reason adequate EQ should be used is that industrial flows often vary in TSS loading. Some rinse waters during production are relatively clean while others are heavily laden with solids. These must Thou shalt prescreen thy water The first order of business is removing large solids or foreign matter from the wastewater. A screen mechanically removes solids, helps reduce chemical usage and protects down-stream equipment from plugging or damage. Plugged and damaged valves, pipes or DAFs do not efficiently remove TSS. Wastewater screens come in a number of designs such as bar or in-channel, side-hill, externally fed and internally fed. Some incorporate shaker mechanisms or self cleaning spray bars. It is important to select the correct screen for a particular application by consulting with vendors and manufacturers.