Field tests were conducted and historical operating data were evaluated to assess the performance of the Monterey WWTP utilizing subsurface flow (SF) constructed wetlands. Previous work with SF wetlands has demonstrated adequate, but variable removal of organic matter, suspended solids, and nitrogen. Few research studies have observed the generation of compounds in the wetlands that affect other treatment processes, specifically reduced compounds that contribute to the chlorine demand. This study attempts not only to distinguish the factors leading to the inadequate performance of the SF wetlands in removing organic matter and nitrogen, but also to identify the cause of the frequent occurrences of a nondetectable chlorine residual in the chlorine contact tank at the Monterey WWTP. Collection and analysis of historical operating data from January 1998 to May 2000 revealed a constantly decreasing removal of carbonaceous biochemical oxygen demand (CBOD5) by the SF wetlands and a poor removal of ammonia-N throughout the system. The decreasing removal of CBOD5 appeared to be caused by clogging of the wetland bed media by accumulated solids. The inability to remove the accumulated solids by pumping was shown. Analysis of field data also showed that the SF wetlands removed 88% of the influent TSS and 71% of the influent CBOD5, while experiencing a 18% increase in ammonia-N. Bisulfide produced in the anaerobic wetland beds accounted for 95% of the chlorine lost in contact tank. The variable production of sulfide is the cause of the frequent nondetectable chlorine concentrations observed. The results of this study suggest that chemical costs of chlorine and sulfur dioxide may be greatly reduced if bisulfide can be removed before chlorination. Also, the use of large rocks as media in SF wetland beds may significantly reduce the physical and biological removal of organic matter. / Master of Science

Constructed wetlands are one of alternative solution wastewater treatment. Compared to conventional wastewater plants have many advantages. For example it´s technology saving construction, low operating costs, cleavability diluted wastewater and little or no need for electrical power. There are many publications dealing with Natural Ways wastewater treatment or even constructed wetlands. I decided to look for a thesis on one of the key processes – clogging bed media. The thesis is focused on ways to prevent clogging of bed media, mitigate the consequences and technology to increase hydraulic conductivity of constructed wetlands. The main test method is improving drainage parameters using pulsed filling and emptying of the bed media. This method is a very effective way to achieve quality requirements for effluent water from the treatment plant. Another test method is based on the injection of air into the media bed and sludge extraction using a specially modified industrial vacuum cleaner or pump.