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Wastewater sludge is a complex raw material that can support growth and protease production by Bacillus licheniformis. In this study, sludge was treated by different thermo-alkaline pre-treatment methods and subjected to Bacillus licheniformis fermentation in bench scale fermentors under controlled conditions. Thermo-alkaline treatment was found to be an effective pre-treatment process in order to enhance the proteolytic activity. Among the different pre-treated sludges tested, a mixture of raw and hydrolysed sludge caused an increase of 15% in the protease activity, as compared to the untreated sludge. The benefit of hydrolysis has been attributed to a better oxygen transfer due to decrease in media viscosity and to an increase in nutrient availability. Foam formation was a major concern during fermentation with hydrolysed sludge. The studies showed that addition of a chemical anti-foaming agent (polypropylene glycol) during fermentation to control foam could negatively influence the protease production by increasing the viscosity of sludge.

A study was conducted to evaluate the nutrient removal capability of an existing and successfully operated overland flow and wetland wastewater treatment system following a waste stabilization pond. Seasonal temperature effects on performance were also investigated. The treatment system studied consists of a two-cell waste stabilization pond followed by an overland flow system and a wetland system. The influent and effluent samples were analyzed for BOD5, suspended solids (SS), pH, temperature, ammonia nitrogen, nitrate nitrogen, and total phosphorus. The results of the study indicate that the combined pond, overland flow and wetland system provided excellent treatment of municipal wastewater. The overall average BOD5 removal by the entire treatment system was about 90.0% and the overall average suspended solids removal was about 93.4%. The ammonia nitrogen and total phosphorus removal efficiencies of the entire treatment system were 90.7% and 84.2%, respectively.

Activated sludge from different full-scale wastewater treatment plants (municipal, pulp and paper industry, starch manufacturing and cheese manufacturing wastewaters) was used as a source of microorganisms to produce biodegradable plastics in shake flask experiments. Acetate, glucose and different wastewaters were used as carbon sources. Pulp and paper wastewater sludge was found to accumulate maximum concentration (43% of dry weight of suspended solids) of polyhydroxy alkanoates (PHA) with acetate as carbon source. Among the different wastewaters tested as a source of carbon, pulp and paper industry and starch industry wastewaters were found to be the best source of carbon while employing pulp and paper activated sludge for maximum accumulation of PHA. High concentration of volatile fatty acids in these wastewaters was the probable reason.

Water reuse is well established in the United States, with uses ranging from pasture irrigation using reclaimed water that has received a low level of treatment, to augmentation of potable water supplies with highly treated reclaimed water. There are no federal regulations governing water reuse and criteria are developed at the state level. Criteria differ between states that have adopted regulations or guidelines, but criteria among states where water reuse is prevalent are similar and tend to be conservative, with public health protection being the most important consideration. The US Environmental Protection Agency (EPA) has published guidelines for water reuse that include recommended criteria for various reclaimed water applications.

Two laboratory scale fluidized-bed biofilm reactors (FBBRs) were used to investigate the biomass concentration and the biofilm characteristics in a high performance FBBR used for the denitrification of exceptionally high-nitrate wastewater (1000mg-N/L). Reported correlations by other workers for predicting the biomass concentration in FBBR were examined for their validity in comparison with the experimental results of this study and the best set of applicable correlations was recommended. The effects of the two main operational parameters, the superficial velocity and nitrogen loading rate on the biomass concentration in the FBBR were also studied. Correlations for the drag coefficient and the expansion index from the literature, together with the biofilm dry density correlation produced from this study were found to produce the best prediction of the FBBR biomass concentration compared to other reported correlations. The average biomass concentration in the FBBR decreased with the increase of the superficial velocity in the range of 45 to 65 m/h at all the applied nitrogen loadings (i.e. 6, 8, 12 and 16kg-N/m3bed·d).

This study focuses on development of aqueous flowable (suspension) formulations for Bacillus thuringiensis (Bt) based biopesticides from wastewater sludge. Different inerts like sorbitol, sodium monophosphate, sodium metabisulphite, sorbic acid, propionic acid, Tween-80, Triton X-100 and glycerol were tested for formulations. Five different formulations for non-hydrolyzed (NH) secondary sludges were tried and the best combination selected on the basis of various physical parameters like viscosity, particle size, suspendibility, entomotoxicity, and microbiological purity tests. F5 formulations (for secondary sludge) comprising sorbitol, sodium monophosphate and sodium metabisulphite gave better physical and biological characteristics with a small effect on entomotoxicity and spore concentration after 120 days at pH 6, 6.5 and temperatures 40 and 50°C and viscosity change at 40 and 50°C. The formulations were more stable at pH 4.0 to 5.0 and temperatures 4 to 30°C whereas at pH 6.0 and 6.5 and temperatures 40 and 50°C, there was degeneration of the product. Lower proteolytic activity and physical factors like ionic strength and surface group changes at pH 6 and 6.5 were responsible for the instability of the formulation.

Production of Bacillus thuringiensis (Bt) based biopesticide was studied using hydrolysed or raw wastewater sludge as a raw material. The sludge hydrolysis was carried out at different pH (2, 4 and 6). The sludge after hydrolysis was sterilised at 121°C for 30 minutes. The effect of temperature, pH and agitation speed on growth and toxin production was also investigated. The pH in the shake flask was controlled by adding 0.1 M TRIS buffer. The progress of the biopesticide production process was monitored by measuring viable cell count (VC), spore count (SC) and entomotoxicity (Tx). The entomotoxicity was measured against spruce budworm. Control of pH substantially increased the entomotoxicity of the final product. Increased agitation speed resulted in higher VC, SC and Tx values.

The simultaneous production of Bacillus thuringiensis (Bt) based biopesticide and proteases was studied using synthetic medium and wastewater sludge as a raw material. The studies were conducted in shake flask and computer controlled 15-L capacity fermentors. Measuring viable cell and spore counts, entomotoxicity and protease activity monitored the progress of the biopesticide production process. A higher viable cell count and spore count was observed in synthetic Soya medium, however, higher entomotoxicity and protease activity were observed in wastewater sludge medium. Thus, the wastewater sludge is a better raw material than commercial Soya medium for the biopesticides and enzyme production. The maximum entomotoxicity and protease activity observed in the fermentor was 9,332 IU/μL and 4.58 IU/mL, respectively. The proteases produced by Bt were also characterised. Two types of proteases were detected; neutral proteases with pH optimum 7.0 and alkaline proteases with pH optimum 10-11. Further, two types of alkaline proteases were detected; one having a pH and temperature optimum at 10 and 50°C while the other at 11 and 70°C. The protease thermal stability was found to increase in the presence of CaCl2, indicating the proteases were metalloproteases.

In this study, the effectiveness of anaerobic treatment systems in reducing pathogenic density levels was evaluated under the US EPA municipal sludge rule (40 CFR Part 503 Rule). Wastewater and sludge samples were analyzed for both pathogens and pathogenic indicator organisms from six different existing wastewater treatment systems. The results indicate that Class B sludge requirements under the US 503 Rule are reasonable and can be achievable by the existing treatment systems while Class A sludge requirements under the same rule may not be easily achieved by the existing treatment systems. The effects of volatile solids loading rates on anaerobic digester performance were investigated. Under anaerobic digestion conditions, it appears that the log reductions in fecal coliform and fecal streptococcus appeared to be dependent on VSS loading rates. On the other hand, Salmonella sp. density reductions did not appear to be dependent on VSS loading rates.

The objective of this study was to demonstrate that municipal and industrial wastewater sludges could be used as a sole raw material to sustain growth of rhizobia. Growth of two different groups of rhizobium (fast growing: Sinorhizobium meliloti, Rhizobium leguminosarum bv viciae; and slow growing: Bradyrhizobium japonicum and Bradyrhizobium elkanii) was tested on primary, secondary and mixed sludges obtained from different wastewater treatment plants. The results obtained in Erlenmeyer flasks indicated that slow- and fast-growing rhizobia grew well in sludge. Generally, the number of cells of rhizobia exceeds 1 × 109 cfu/mL in 72 h. The composition of sludges varies with the sludge type and origin. The sludge composition affected the generation time, cell yield and nodulation index. Higher solids concentration tended to give higher generation time. The high sludge metals concentration did not affect the growth kinetics of rhizobia. However, primary sludge could inhibit cell growth. Acid, alkaline and oxidative pre-treatments increased the primary sludge biodegradability and consequently the cell count of S. meliloti. Pre-treatment of pulp and paper sludge with NaOH enhanced the bacterial cell concentration to a maximum 1 × 1010 cfu/mL. Sludge pre-treatment decreased the generation time and reduced the process time.

This paper documents the performance of a subsurface-flow constructed wetlands system during its initial five years of operation under variable loading and operating conditions associated with a northern midwestern US climate. The results indicate that effective and sufficient CW seasonal removals of TSS, VSS, CBOD5, COD, and fecal coliform were achieved. Wastewater temperatures seemed to affect CBOD5 and COD removal rates. Nitrogen and phosphorus reductions were not as effective and varied seasonally, as well as with wastewater temperature. The addition of a sand filter, to aid in further nitrification and disinfection following CW treatment, markedly improved the performance of the wetlands system. After a few years of operation, the remarkable performance of the CW system was dampened by apparent clogging and subsequent eruption of wastewater at the head-end of the treatment cells. While clogging was partially caused by biomass build-up in the wetlands substrate, visual observations suggest that excessive vegetation coupled with relaxed maintenance may also be responsible for clogging.

A subsurface flow constructed wetlands (CW) system, located at a neighborhood consisting of a small housing development and golf courses outside of Lincoln, NE, was studied for its effectiveness as a small community wastewater system. Extensive monitoring was conducted biweekly between June 1996 and December 2000. Prediction models for soluble CBOD5 NH3-N, and TP removal in CW were employed for comparison with the field data. It was found that the disappearance of BOD5 and NH3-N could be approximated using first-order kinetics, but the kinetics of TP removal were unclear. The reduction rate constants regressed from the field data were found to be lower than literature reported values.

Increasing demands on water resources for domestic, commercial, industrial, and agricultural purposes have made water reclamation and reuse an attractive option for conserving and extending available water supplies. Also, many water reuse projects are implemented to eliminate a source of contamination in surface waters or as a least-cost alternative to meeting stringent discharge requirements. Reclaimed water applications range from pasture irrigation to augmentation of potable water supplies. Water reclamation and reuse criteria are principally directed at health protection. There are no federal regulations governing water reuse in the U.S.; hence, the regulatory burden rests with the individual states. This has resulted in differing standards among states that have developed criteria. This paper summarizes and compares the criteria from some states that have developed comprehensive regulations. Guidelines published by the US. EPA and the rationale behind them are presented for numerous types of reclaimed water applications.

Distribution of cadmium and nickel between operationally defined soluble and solid phases of activated sludge was investigated. The metal sorption process was characterized by describing it quantitatively as a function of time, pH and suspended solids concentration. Reversibility of the sorption process was studied by comparing metal adsorption and desorption edges. The effect of desorption kinetics on hysteresis of nickel was investigated. Equilibrium adsorption isotherms were developed for cadmium and nickel in activated sludge at different pH levels, and sorption capacity of solids and conditional stability constants for metals-sludge reactions were determined using the Langmuir adsorption model.

Rotating biological contactors (RBCs) have been used extensively, but the process units had structural and operational problems. The main problems were related to low dissolved oxygen levels, resulting in thicker biomass growth in the initial stages. This paper discusses the observed value of supplemental aeration in improving RBC performance and in ensuring longer media and shaft life because of reduced mass of biofilm growth. Three full-scale upper-midwest RBC plants, having supplemental aeration in the first two stages, were studied to determine the value of supplemental air in improving RBC performance and in controlling Beggiatoa growth. These plants were operated over a fairly wide range of organic loading. The study results indicated that it was possible to achieve higher BOD5 removal rates when RBCs were provided with supplemental air. In addition, higher dissolved oxygen levels, resulting from the supplemental air, enhanced BOD5 removal and ammonia nitrification significantly. The resulting thinner biofilms also ensured longer life for the media and shaft. Supplemental aeration can be provided with nominal capital investment.

A full-scale, four-stage RBC (rotating biological contactors) plant, having parallel trains used to treat domestic and industrial dairy wastewater, failed to meet standard secondary effluent limits due to overloading in the two initial stages. The plant was first operated under normal loading; subsequently the load to the plant was increased in an incremental fashion by increasing the load from the dairy. This was done to evaluate the effectiveness of the use of supplemental aeration to eliminate oxygen-limiting conditions in the overloaded stages. An enlarged first stage was later created to lower the organic load to the initial stages by removing the wooden baffles between the first and second stages. The experimental work at the plant was conducted for approximately six months, during which daily 24-hour composite samples were collected at the end of each stage and analyzed for various parameters. The experimental results indicated that substrate removal with supplemental air and an enlarged first stage followed first-order kinetics at both lower and higher organic loadings. Without supplemental air, substrate removal followed second-order kinetics at lower loadings and zero-order kinetics at higher organic loadings. With an enlarged first stage only, substrate removal followed first-order kinetics at lower loading and zero-order kinetics at higher loadings. Overall, RBC performance improved significantly with supplemental air and an enlarged first stage. The results also suggest that higher organic loadings and removals can be achieved in the presence of supplemental air due to the maintenance of higher dissolved oxygen levels in the mixed liquor.

The municipal lagoon treatment systems which remove phosphorus by chemical addition are the subject of this special study. The objectives of this study were to determine the degree of success of lagoon treatment systems in removing phosphorus and to identify any operational problems. In order to obtain basic data for this study, thirty-two lagoon treatment systems in Michigan and Minnesota were investigated. Chemicals typically used for phosphorus removal include metal salts such as aluminium sulfate (alum), ferrous and ferric chloride, lime, and various polymers. The overall experience with these lagoon systems is that the technology, in its various configurations, has been working very well. Of the thirty-two lagoon treatment facilities reviewed, only two facilities were having problems meeting consistently the effluent phosphorus limits. Generally, the permitted effluent phosphorus limit is 1 mg/l. The influent phosphorus concentrations varied between 0.5 and 15 mg/l. Alum and ferric chloride applications produced consistently high quality effluents while lime applications were not as effective in removing phosphorus. None of these lagoon treatment systems experienced problems with build-up of sludges to levels which affected the effluent concentrations. Accumulated amounts were an inch or less per year, consistent with solids build-up in the primary lagoon cells.