Texas Waste Water Treatment Ch#01 Introduction

The following are benefits gained from the complete treatment of wastewater: • Protection of public health from waterborne disease • Protection of the natural environment and the wildlife that depends on it • Elimination of nuisance conditions • Protection of downstream water supplies • Conservation of water for reuse • Removal of toxic and hazardous materials • Protection of water sources for recreational use • Prevention of deposits of solids in lakes, streams, and rivers

National, state, and local governments set the standards for treatment. These requirements depend on treatment plant location, the water quality standards set for the receiving stream, and the amount and final use of the effluent. Different treatment plants have different requirements. NOTE: the idea is not to make fresh drinking water but to process waste water to the point that it matches or exceeds the quality of the water way it will be discharged into.

Wastewater treatment involves a series of steps with two goals: (1) a clean effluent discharge, and (2) proper sludge disposal. The steps are as follows: 1. Source pretreatment 2. Wastewater collection 3. Cross-connection control 4. Preliminary treatment 5. Primary treatment 6. Secondary treatment 7. Advanced treatment 8. Disinfection 9. Effluent discharge 10. Sludge treatment and disposal

The collection system may include the following: • Collection lines • Collection system entries (manholes) • Pump stations • Grease and sand traps • Inverted siphons • Diversion structures NOTE: The waste water COLLECTION system is everything required to get waste water to the processing plant of which pipes for liquid transport and manholes for cleaning and access are >essential< to that function. Cross connections are any connection between potable and non-potable water systems which should not mix. Infiltration structures and flooded lift stations are fictitious options to throw you off.

The following aspects of the collection system can affect wastewater: • Excessive infiltration of groundwater or inflow of storm water into the collection system • Flat grades or low spots in the collection system that cause wastewater to flow more slowly and allow more time for bacterial action • Poorly designed, constructed, or maintained collection systems • High temperatures and unventilated collection lines • High organic loads that quickly deplete available oxygen supply • Poorly maintained and operated lift stations • Industrial waste discharges

As the wastewater enters the treatment plant, preliminary treatment removes materials that might interfere with proper treatment, cause damage, or cause excessive wear on system components (Figure 1.4). Important aspects of preliminary treatment include the following: • Coarse or fine screening • Grinding • Grit removal • Grease removal • Pre-aeration • Flow equalization • pH adjustment NOTE: Grit removal is usually accomplished in preliminary treatment because it is necessary to protect equipment further in the process and so that plant employees can maintain the grit removal equipment in a cost effective manner.

In secondary treatment, microscopic living creatures called microorganisms remove additional contaminants from the wastewater. Conditions are purposely created that favor the growth and reproduction of treatment microorganisms. These organisms trap and consume waste, using contaminants in wastewater as their food supply. After these organisms are later removed as biological solids, the wastewater will be less contaminated. NOTE: The purpose of the microorganisms.... is to BE the biology in "biological treatment" they eat things and turn them into other things that are more easily removed than the original contaminants.

Biological secondary treatment processes may include any of the following: • Stabilization ponds • Trickling filters • Rotating biological contactors • Activated sludge systems • Sand and rock beds • Hyacinth ponds • Overland flow systems • Mechanically aerated ponds NOTE: An RBC is an alternative to a trickling filter that is also used for biological secondary treatment.

Disinfection destroys or inactivates pathogenic (disease-causing) bacteria, viruses, and protozoa. These infectious agents can cause outbreaks of dysentery, typhoid, hepatitis, cholera, or other diseases if not eliminated during wastewater treatment. NOTE: The purpose of the disinfection process is to eliminate microorganisms in the waste water. this includes both the helpful ones used in the treatment process and pathogens that come in with raw waste water.

Disposal methods for wastewater sludge include: • disposal in landfills; • application on farm land or forest land; • incineration; • disposal in lagoons; and • application for commercial purposes.

Using reclaimed wastewater for irrigation frees up fresh water to be used for other purposes while also acting as fertilizer.

Stabilization is a chemical or biological process that stops the natural fermentation of the sludge.

hauling sludge anywhere is not generally used specifically as a method of dewatering, incineration, or stabilization

Each treatment facility while similar must be tailored to the area and population it serves to maximize efficiency.